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Wideband acoustic immittance : instrument, ethnicity, and gender specific normative data Jaffer, Sukaina 2016

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WIDEBAND ACOUSTIC IMMITTANCE: INSTRUMENT, ETHNICITY, AND GENDER SPECIFIC NORMATIVE DATA by  Sukaina Jaffer  Hon. B.Sc., The University of Toronto, 2010  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF  MASTER OF SCIENCE in THE FACULTY OF GRADUATE AND POSTDOCTORAL STUDIES (Audiology and Speech Sciences)  THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver)   April 2016  © Sukaina Jaffer, 2016  ii Abstract   This study investigated whether wideband acoustic immittance (WAI) values differed significantly in a normal hearing young adult population based on gender, ethnicity, and instrument. Normative data collected from this study can be utilized to create a repository of norms for clinical use as suggested by consensus among researchers in the Eriksholm Workshop. Eighty normal hearing young adults (age 18-34) were recruited from the University of British Columbia to undergo WAI testing with two hand-held devices (Otostat Mimosa Acoustics and Titan Interacoustics) and two non-portable devices (Reflwin Interacoustics and Mimosa Acoustics HearID). Approximately twenty participants were recruited from each of the male, female, Caucasian and Chinese groups. It was found that Caucasians had significantly higher mean power absorbance (PA) in the low frequencies between 630 – 1250 Hz and the Chinese had significantly higher mean PA in the high frequencies from 5000 - 6300 Hz overall collapsed across all devices. When the effect of equivalent ear canal volume (ECV) was adjusted for, mean PA for females were significantly higher than males at high frequencies between 4000 – 6300 Hz depending on the device used and at 5000 Hz across all devices. Mean PA at peak pressure were significantly higher than ambient pressure between 250 – 2000 Hz and significantly lower between 3150 – 5000 Hz collapsed across all devices tested (ReflWin and Titan), genders, trials, ears, and ethnicities. Mean PA did vary slightly across some frequencies for the Interacoustics devices but not the Mimosa Acoustics devices between trials; however, the test-retest differences were no more than those observed across various studies of a normal hearing population and much smaller than the difference between normal and pathological ears indicating good reliability. Mean PA varied across frequencies between devices, but using HearID instrument  iii specific data didn’t greatly improve the ability to distinguish the normal group from a sample with surgically confirmed otosclerosis obtained using the HearID system at 800 and 2000 Hz. It is advised that future investigations utilize gender, ethnicity, and instrument-specific data to determine whether these factors improve the sensitivity and specificity of identifying middle ear pathologies using a larger frequency bin for analysis.   iv Preface  This thesis is based on work conducted at UBC’s Middle Ear Lab by Dr. Navid Shahnaz, Ainsley Ma, Shahab Ravanparast, and Sukaina Jaffer. I contributed to the identification of the research question and methodology with great guidance from Dr. Navid Shahnaz. I was responsible for writing of the thesis, carrying out the procedures proposed in the study along with statistical analysis of research data. I was also responsible for briefing new lab members on the test procedures and analysis to be carried out in the study. Ainsley Ma and Shahab Ravanparast contributed greatly to the scheduling of participants, testing, and data extraction in the study. Allison Beers and Dr. Tony Herdman were thesis committee members who provided great input to the writing of this paper.      v Table of Contents Abstract .......................................................................................................................................... ii	Preface ........................................................................................................................................... iv	Table of Contents ...........................................................................................................................v	List of Tables .............................................................................................................................. viii	List of Figures .................................................................................................................................x	List of Abbreviations ...................................................................................................................xv	Acknowledgements .................................................................................................................... xvi	Dedication .................................................................................................................................. xvii	Chapter 1: Introduction ................................................................................................................... 1	1.1	 Basic Principles of Wideband Acoustic Immittance .................................................. 5	1.2	 Effect of Gender .......................................................................................................... 4	1.3	 Effect of Ethnicity ....................................................................................................... 6	1.4	 Effect of Instrument .................................................................................................... 7	1.5	 Effect of Ear Canal Pressurization on Power Absorbance Measurements ............... 10	1.6	 Test-Retest Reliability of PA Measurements ............................................................ 12	1.7	 Wideband Tympanometry ........................................................................................ 16	1.8	 Other Variables Measured in the Study .................................................................... 20	1.9	 Reflectance Phase Angle and Admittance Magnitude .............................................. 26	1.10	Hypothesis................................................................................................................. 29	Chapter 2: Methods ....................................................................................................................... 31	2.1	 Sample Group ........................................................................................................... 31	2.2	 Inclusion Criteria ...................................................................................................... 32	 vi 2.3	 Wideband Acoustic Immittance Devices .................................................................. 33	2.4	 Measurements in the Study ....................................................................................... 40	2.5	 Statistical Analysis .................................................................................................... 42	Chapter 3: Results ......................................................................................................................... 45	3.1	 Effect of Instrument, Ethnicity, Gender, and Ear on PA at Ambient Pressure ......... 45	3.2	 Effect of Ambient vs. Peak Pressure on PA between Titan and ReflWin Systems .. 63	3.3	 Covariates of Power Absorbance .............................................................................. 78	3.4	 Other Variables ......................................................................................................... 84	Chapter 4: Discussion ................................................................................................................... 99	4.1	 Summary ................................................................................................................. 100	4.2	 Possible Covariates of Power Absorbance ............................................................. 107	4.3	 The Effect of Ethnicity, Gender, and Ear on PA at Ambient Pressure ................... 112	4.4	 Test-Retest Reliability for PA Measurements at Ambient Pressure ....................... 120	4.5	 The Effect of Instrument on PA Measurements at Ambient Pressure .................... 124	4.6	 The Effect of Ethnicity, Instrument, Gender, and Ear on Ambient vs. Peak Pressure Measurements ......................................................................................................... 138	4.7	 The Effect of Gender, Instrument, and Ethnicity on Frequency-Averaged PA Using Wideband Tympanometry ...................................................................................... 146	4.8	 Reflectance Area Index (RAI) ................................................................................ 151	4.9	 Reflectance Phase Angle and Admittance Magnitude ............................................ 153	4.10	Limitations and Future Directions .......................................................................... 160	Chapter 5: Conclusion ................................................................................................................. 164	Bibliography ............................................................................................................................... 169	 vii Appendices .................................................................................................................................. 185	  viii List of Tables  Table 1 Mean and standard deviation of power absorbance values measured at ambient pressure using all four WAI instruments for frequencies between 250 – 8000 Hz averaged across all trials, genders, and ethnicities. Note that HearID doesn’t provide PA measurements at 8000 Hz. ........ 46	Table 2 Mean PA averaged across 2 trials from 250 – 8000 using 4 WAI devices in the Chinese group. Note that HearID doesn’t provide information at 8000 Hz. .............................................. 48	Table 3 Mean PA averaged across 2 trials from 250 – 8000 using 4 WAI devices in the Caucasian group. Note that HearID doesn’t provide information at 8000 Hz. ............................. 49	Table 4 Descriptive statistics table including mean and standard deviation of PA measurements obtained from 250 – 8000 Hz (in 1/3 octave frequencies for a total of 16 frequencies) at ambient pressure organized based on categories of instrument, trials, and genders for the Chinese participants. ................................................................................................................................... 58	Table 5 Descriptive statistics table including mean and standard deviation of PA measurements obtained from 250 – 8000 Hz (in 1/3 octave frequencies for a total of 16 frequencies) at ambient pressure organized based on categories of instrument, trials, and genders for the Caucasian participants. ................................................................................................................................... 59	Table 6 Mean and standard deviation of power absorbance values using two Interacoustics devices (Titan and ReflWin) at both ambient and peak pressure for frequencies between 250 – 8000 Hz averaged across all trials, genders, ears, and ethnicities. ............................................... 64	Table 7 Descriptive statistics including the mean and standard deviation of parameters including resonance frequency (RF), peak tympanometric peak pressure (TPP), static admittance (Ytm) and reflectance area index (RAI). ................................................................................................. 85	 ix Table 8 descriptive statistics, including mean and standard deviation of admittance magnitude (Y) values obtained with ReflWin across frequencies from 250 – 8000 Hz for categories of ethnicity and gender. ..................................................................................................................... 93	Table 9 Summary of AUROC plots and 95% CI along with pair-wise comparison of AUROC plots for PA at 800 Hz between HearId (HiD) at ambient pressure, Otostat (Ot) at ambient pressure, ReflWin (Ref) at ambient pressure, Titan at ambient pressure, ReflWin at peak pressure, and Titan at peak pressure. All highlighted cells represent pairwise comparisons which were significant (p < 0.05). ......................................................................................................... 135	Table 10 Summary of AUROC plots and 95% CI along with pair-wise comparison of AUROC plots for PA at 2000 Hz between HearId (HiD), Otostat (Ot), ReflWin (Ref), and Titan at ambient pressure along with ReflWin and Titan at peak pressure. All highlighted cells represent pairwise comparisons which reached significance. .................................................................... 136	 x List of Figures  Figure 1 A depiction of the frequency averaged PA (between 0.38 – 2 kHz) as a function of air pressure. Each panel shows the results at a different sweep speed and direction. The traces show responses from individual ears (N=92). Reprinted with permission from Liu, Y., Sanford, C.A., Ellison, J.C., Fitzpatrick, D.F., Gorga, M.P., & Keefe, D.H. (2008). Wideband absorbance tympanometry using pressure sweeps: system development and results on adults with normal hearing. J. Acoust Soc. Am., 124, 3708–3719. Copyright 2008, Acoustic Society of America. .. 19	Figure 2 Illustration of the Mimosa Acoustics HearID hardware are depicted. The USB Audio Processing Unit, MEPA Calibration Cavity Set, Etymotic ER10C probe, and a selection of eartips. Reprinted with permission from Mimosa Acoustics, Inc. ................................................ 34	Figure 3 Illustration of the Reflwin Interacoustics WAI system. The assembly includes the AT235h audiometer used for changing the pressure in the ear canal and a probe tip (bottom right) which is connected to a PC. Reprinted with permission from ReflWin Interacoustics, Inc. ........ 36	Figure 4 Illustration of the Titan Interacoustics system. The handheld unit can be used independently or while connected to the PC. Reprinted with permission from Interacoustics, Inc........................................................................................................................................................ 38	Figure 5 Hand-held Otostat Mimosa Acoustics hand-held unit includes a calibration cavity set, probe, ear tips, USB cable, and power adaptor. Reprinted with permission from Mimosa Acoustics, Inc. ............................................................................................................................... 39	Figure 6 Mean PA at ambient pressure displayed in 1/3rd octave intervals from 250 – 6300 Hz is shown for the 2 ethnicities across 4 instruments (ReflWin, HearID, Otostat, and Titan). Vertical bars denote 95% confidence intervals (CIs). ................................................................................ 50	 xi Figure 7 Mean PA at ambient pressure displayed at 1/3rd octave intervals from 250 – 6300 Hz for the 2 ethnicities collapsed across all devices, genders, and ears. Vertical bars denote 95% CIs........................................................................................................................................................ 52	Figure 8 Depicts mean PA values at ambient pressure as a function of frequency (in 1/3rd octave intervals) from 250-6300 Hz for the 2 genders across 4 instruments (ReflWin, HearID, Otostat, and Titan). Vertical bars denote 95% CI. ..................................................................................... 53	Figure 9 Depicts mean PA at ambient pressure as a function of frequency from 250 – 6300 Hz for the 2 genders collapsed across all devices, ethnicities, and ears. Vertical bars denote 95% CI........................................................................................................................................................ 55	Figure 10 Depicts mean power absorbance (PA) at ambient pressure in 1/3rd octave intervals from 250-6300 Hz for the ReflWin, HearID, Otostat and Titan instruments. Vertical bars denote 95% confidence intervals (CI). ..................................................................................................... 57	Figure 11 Mean power absorbance (PA) in 1/3rd octave intervals from 250-8000 Hz is shown across frequencies collapsed across all systems, trial numbers, ethnicities, genders and ears. Vertical bars denote 95% confidence intervals (CI). .................................................................... 66	Figure 12 Mean power absorbance (PA) in 1/3rd octave intervals from 250-8000 Hz is shown for the two genders collapsed across all systems, pressurization methods, trial numbers, ethnicities and ears. Vertical bars denote 95% confidence intervals (CI). ..................................................... 68	Figure 13 Mean power absorbance (PA) made at ambient and peak pressure is shown in 1/3rd octave intervals from 250-8000 Hz for the 2 genders collapsed across all systems, trial numbers, and ears. Vertical bars denote 95% confidence intervals (CIs). ................................................... 69	 xii Figure 14 Mean power absorbance (PA) made at ambient and peak pressure is shown in 1/3rd octave intervals from 250-8000 Hz for the 2 ethnicities collapsed across all systems, trial numbers, and ears. Vertical bars denote 95% confidence intervals (CIs). ................................... 71	Figure 15 Mean power absorbance (PA) values depicted in 1/3rd octave intervals from 250-8000 Hz obtained at peak pressure and ambient pressure using either the ReflWin or Titan systems.  Vertical bars denote 95% confidence intervals (CI). .................................................................... 74	Figure 16 Mean power absorbance (PA) values depicted in 1/3rd octave intervals from 250-8000 Hz obtained using either the ReflWin or Titan systems at peak pressure and ambient pressure.  Vertical bars denote 95% confidence intervals (CI). .................................................................... 75	Figure 17 Mean power absorbance (PA) values depicted in 1/3rd octave intervals from 250-8000 Hz obtained using the ReflWin and Titan systems during trial 1 and trial 2. Vertical bars denote 95% confidence intervals (CI). ..................................................................................................... 77	Figure 18 Depicts equivalent ear canal volume measured using all 4 systems at a frequency at or near 226 Hz for both genders. ....................................................................................................... 81	Figure 19 Depicts equivalent ear canal volume measured using all 4 systems at a frequency at or near 226 Hz for both ethnicities. ................................................................................................... 82	Figure 20 Frequency-averaged power absorbance between 375 – 2000 Hz measured by the Titan system is plotted across pressure from +100 to -100 daPa for both genders. Vertical bars represent 0.95 CIs. ........................................................................................................................ 88	Figure 21 Frequency-averaged power absorbance averaged between 375 – 2000 Hz measured by the Titan system is plotted across pressure from +100 to -100 daPa for both ethnicities. Vertical bars represent 0.95 CIs. ................................................................................................................. 89	 xiii Figure 22 Admittance phase in degrees measured by the ReflWin system is plotted from 250 – 8000 Hz for both genders. Vertical bars represent 0.95 CIs. ........................................................ 91	Figure 23 Admittance phase measured by the ReflWin system (in degrees) is plotted from 250 – 8000 Hz for both ethnicities. Vertical bars represent 0.95 CIs. .................................................... 92	Figure 24 Admittance magnitude (in dB) obtained by the ReflWin is plotted from 250 – 8000 Hz for both genders. Vertical bars represent 0.95 CIs. ....................................................................... 95	Figure 25 Admittance magnitude (in dB) obtained by the ReflWin system is plotted from 250 – 8000 Hz for both ethnicities. Vertical bars represent 0.95 CIs. .................................................... 96	Figure 26 Reflectance phase (in rd/2d π) measured by the HearID system is plotted from 258 - 6000 Hz for both genders. Vertical bars represent 0.95 CIs. ........................................................ 98	Figure 27 A graph comparing differences in mean PA values between trials (using values from the descriptive statistics chart in the Appendix) across frequencies for all four systems to demonstrate differences in mean PA values between normal ears (obtained in trial 1) for each instrument and those with surgically confirmed otosclerosis. .................................................... 123	Figure 28 A depiction of the average PA values and standard deviations across frequency using the ReflWin Interactoustics in the current study at ambient pressure as compared to earlier versions of the device documented in the literature. ................................................................... 128	Figure 29 A depiction of the average PA values and standard deviations across frequency using the Mimosa Acousics devices (HearID and Otostat) in the current study as compared to earlier versions of the PC-based Mimosa devices documented in the literature. ................................... 129	Figure 30 A depiction of the average PA values and standard deviations across frequency using the Titan Interacoustics device in the current study as compared to the Titan Interacoustics device used in a fairly recent study by Polat et al. (2015) at ambient pressure. ......................... 130	 xiv Figure 31 Receiver operating characteristic curve analysis for power absorbance values at 800 Hz using the HearID at ambient pressure, Otostat at ambient pressure, ReflWin at ambient and peak pressure, and Titan at ambient and peak pressure. ............................................................. 133	Figure 32 Receiver operating characteristic curve analysis for power absorbance values at 2000 Hz using the HearID at ambient pressure, Otostat at ambient pressure, ReflWin at ambient and peak pressure, and Titan at ambient and peak pressure. ............................................................. 134	  xv List of Abbreviations ANOVA Analysis of variance AUROC Area under the receiver operating curve daPa deka pascal DPOAE Distortion-product otoacoustic emissions PA Power Absorbance PR Power Reflectance HSD Honestly significant difference Hz Hertz ROC Receiver operating characteristic TPP Tympanometric peak pressure ECV Equivalent ear canal volume WAI Wideband acoustic immittance WT Wideband tympanometry Ytm Static admittance Y Admittance magnitude WT Wideband tympanometry RF Resonance frequency Y Admittance magnitude dB Decibels  RAI Reflectance Area Index BMI Body Mass Index   xvi Acknowledgements  I offer my enduring gratitude to Dr. Navid Shahnaz for his direction and supervision as my Thesis Advisor. His wisdom, penetrating questions, and enthusiasm for my progress made for a successful and enjoyable journey in the completion of this thesis. I am honored to have had the opportunity to learn from him and trust that the knowledge he has imparted upon me throughout my time at UBC will be invaluable as I begin my work as a clinician.   I am also very grateful for the support of and suggestions made by my committee members Dr. Tony Herdman and Allison Beers. Special thanks are due to my colleagues Ainsley Ma and Shahab Ravanparast for their encouragement and support in carrying out this endeavor. I must also thank my clinical co-ordinator, faculty, and administrative staff at UBC who have offered kind words of encouragement and prepared me for the road ahead. You know who you are.   Thank you to my colleagues and the overwhelming number of residents from St. John’s College who demonstrated a keen interest in my work and who were always willing to lend me their ears. I can assure you that your commitment to research will help improve the quality of audiology services in the years to come.  Finally, I would like to thank my lovely parents (Jameela Jaffer and Rustam Jaffer) and brother (Mustafa Jaffer). Without your moral and financial support, I would never have made it this far.   xvii Dedication  For Jameela and Rustam Jaffer    1 Chapter 1: Introduction  Wideband Acoustic Immittance (WAI) is a quick, reliable, objective, cost-effective tool for the assessment of middle ear function. It can quantify the reflected or absorbed sound energy in the ear canal across a wide range of frequencies important for speech and language comprehension (Hunter & Shahnaz, 2014). Complex sounds (typically clicks or chirp stimuli) ranging from 200 to 10 000 Hz or higher are presented into the ear canal and the amount of acoustic energy reflected back from the middle ear is calculated in the form of pressure reflectance (Liu et al., 2008).  One of the parameters used to quantify WAI measurements is power reflectance (PR) or energy reflectance (ER), which is a square of the pressure reflectance. PR is a real number expressed without dimension and only in magnitude not phase; it varies from zero indicating all energy has been absorbed into the middle ear to one meaning all energy has been reflected back from the middle ear (Stinson, 1990).  This paper will consistently use the term power absorption (PA) to refer to the incident sound energy absorbed by the middle ear. PA is a real number and the complement of PR. It is expressed as PA = 1 – PR (Sanford et al., 2013; Neely, Stenfalt, & Schairer, 2013) and can either be represented on a linear scale ranging from 0.0 to 1.0 or on a log scale (10Log10 PA) as absorbance level (Feeney et al., 2013). Pressure reflectance phase characterizes the temporal characteristics of WAI (Feeney et al., 2013). Power reflectance phase is derived from pressure reflectance and provides information about how the wave was propagated across a range of frequencies into the ear during WAI testing (Mimosa Acoustics Inc., 2012). Information about reflectance phase may be useful in assessing the presence of acoustic leaks in ear-canal measurements and identifying other potential sources of errors (Rosowski, Stenfelt, & Lilly, 2013).    2 The application of WAI in clinical assessment has only recently emerged; it has a number of diagnostic advantages over conventional tympanometry and multi-frequency tympanometry. WAI assesses middle ear function more rapidly over a wider range of frequencies compared to conventional tympanometry or multi-frequency tympanometry alone (Vander Werff, Prieve & Geogantas, 2007).  Also, since WAI doesn’t rely on the calculation of ear canal volume between the probe and the ear drum to determine static admittance at the level of the ear drum as in tympanometry, the location of the probe in the ear canal is not as critical in assessing middle ear function in adults and children especially at high frequencies (Huang, Rosowski, & Peake, 2000; Stinson, Shaw, & Lawton, 1982; Voss & Allen, 1994). Voss et al. (2008) found that measures of WAI (PA and PR) are relatively stable and independent of location for much of the length of the ear canal that is in close proximity to the tympanic membrane (TM) or more specifically the osseous bony portion of the canal as opposed to the cartilaginous portion. This is also due to the fact that WAI measurements are less sensitive to standing waves in the ear canal compared to measurements of admittance or impedance (Margolis et al., 1999).   226 Hz tympanometry has been deemed ineffective for use in young infants as it has been known to demonstrate normal tympanograms in many cases of middle-ear effusion and double-peaked tympanograms which cannot be evaluated in this population (Alaerts, Luts, & Wouters, 2007; Vanderwarff, Georgantas, & Prieve, 2007). There has been research to suggest that higher frequency probe tones could identify conductive hearing loss in infants (Paradise, Smith, & Bluestone, 1976; Hunter & Margolis, 1992; Keefe & Levi, 1996; Alaerts, Luts, & Wouters, 2007). While this is promising, it is known that introducing negative and positive air pressure distends infant ear canals in addition to modifying the middle ear which violates underlying   3 assumptions of tympanometry (Margolis & Shanks, 1990; Vanderwarff, Georgantas, & Prieve, 2007). Onuska (2004) states that tympanometry is not reliable in infants younger than seven months given the highly compliant nature of infant ear canals. There is a great need for diagnostic tests that can assist in clinical decisions regarding middle ear dysfunction and conductive hearing loss. WAI tests performed at ambient pressure are quick, objective, cost-effective, and do not require pressurization of the ear canal to assess middle ear status.   Compared with standard 226 Hz tympanometry, WAI may provide for a more sensitive test in evaluating middle ear disorders and conductive hearing loss (Beers et al., 2010; Feeney, Grant, & Maryott, 2003).  For instance, Beers et al. (2010) found that WAI measurements at 1250 Hz were significantly better at identifying ears with middle ear effusion compared to static admittance using 226-Hz probe tone frequency. In addition, a study by Ellison et al. (2012) suggests that the accuracy of diagnosing middle ear effusion utilizing PA is similar to performing pneumatic otoscopy. A review by Prieve et al. (2013) found that multivariate statistical measures which combine WAI across frequency are superior to using WAI in one frequency band and tympanometry at a single frequency for detecting air-bone gaps of 15 to 30 dB in children. Keefe et al. (2012) found that PA (at both ambient and peak tympanometric pressure) was a better predictor of conductive hearing loss than either tympanometric width or peak-compensated static admittance at 226Hz.  Conductive hearing loss with intact tympanic membranes (TM) and aerated middle ears are difficult to differentially diagnose in the clinic; they could potentially be associated with three conditions: ossicular fixation (usually from otosclerosis), ossicular discontinuity, and superior semicircular canal dehiscence (Nakajima et al. 2012). Nakajima et al. (2012) reported that the combination of audiometry with WAI showed good clinical utility in the   4 differential diagnosis of conductive hearing loss in these cases. Specifically, they reported 86% sensitivity and 100% specificity for stapes fixation, 83% sensitivity and 96% specificity for ossicular discontinuity, and 100% sensitivity and 95% specificity for semicircular canal dehiscence. These numbers should be interpreted with caution due to the small sample size (N = 31) in their study. Otosclerosis is often difficult to diagnose when utilizing conventional tympanometry due to an overlap of tympanometric configurations presented in some of these cases with the normal population (Browning et al., 1985; Shahnaz & Polka, 1997). Shahnaz et al. (2009) found that PA was the most effective way of identifying ears with otosclerosis compared to 226 Hz tympanometry and multi-frequency tympanometry. PA was able to identify otosclerosis in 82% of their sample and had a false positive rate of 17.2%. Their study suggests that the use of PA in a test battery including other tools of middle ear function will improve the identification of otosclerotic ears in a clinical setting. In addition, WAI is safer and more useful to utilize in comparison to tympanometry to objectively evaluate the impact of the various stapedial reconstructive surgery protocols and prosthetic devices on middle ear transmission properties (Shahnaz, Longridge, & Bell, 2009). However, the pressure change required for tympanometry can move the stapedial prosthesis more readily as the placement of the prosthesis eliminates the resistance of the annular ligament in the middle ear (Shahnaz, Longridge, & Bell, 2009).  WAI tests performed at ambient pressure do not perturb the placement of the stapedial prosthesis after surgery.   Participants of the Eriksholm Workshop on WAI measures developed a consensus statement regarding important areas of research in this realm (Feeney et al., 2013). The authors acknowledged that normative data collection is still in its infancy, but that a shared data   5 repository for norms should be developed. Parameters they suggested for data inclusion included the specific WAI system used, participant age, gender, ear, and ethnicity. They stated that investigations related to the consistency of WAI measurements across different commercial systems in adults and children are needed. In addition, acceptable limits for clinical test-retest variability and guidelines for determining the validity of WAI test measurements also need to be established. For this reason, Keefe et al. (2000) suggest calculating an equivalent volume at low frequencies, where a negative volume suggests an acoustic leak. Voss et al. (2013) suggest taking phase angle into account, ensuring that phase angle of impedance is relatively flat with frequency, negative at most frequencies below 500 Hz and impedance magnitudes are within specific bounds. However, these bounds were not identified in the review by Voss et al. (2013) due to the dearth of research surrounding this area. There was a consensus during the Erikshom Workshop that the value of characterizing the temporal aspect of WAI through pressure reflectance phase has been ignored to date and there is a need to include this parameter in future studies to determine its utility in identifying acoustic leaks.     1.1 Basic Principles of Wideband Acoustic Immittance Power Reflectance varies by frequency and pressure; it is mathematically defined as follows: PR (f, P) = 1 – ZcY (f, P)                    1 + ZcY (f, P) This formula states that PR is defined as the ratio of 1 minus the product of the characteristic impedance (Zc)1 and admittance (Y)2 at different frequencies (f) and static pressures (P) and 1 plus the product of admittance and characteristic impedance at different frequencies (f) and static pressures (P) (Keefe & Levi, 1996).  As discussed above, PA is the complement of PR defined as  1. The characteristic Impedance (Zc) of the ear canal is defined as Zc   =  pc/s where p is density, c is speed of sound and s is cross-sectional area of the ear canal in the plane of the measurement. 2. Admittance Y (f) is defined as Y(f)   =  1 / Z(f) where Z is the acoustic impedance at frequency f.    PA = 1- PR  Immittance encompasses the terms admittance and impedance. The term admittance (Y) refers to the acoustic energy that flows into the middle ear system and is the parameter most commonly assessed by 226 Hz tympanometry and multi-frequency tympanometry (Shahnaz & Davies, 2006). Impedance (Z) is the total opposition to the flow of acoustic energy within the middle ear system. Acoustic impedance varies with frequency as the relative contributions of acoustic resistance (R) and acoustic reactance (X) change (Feeney, Grant & Marryott, 2003). Measures of PR are dependent on how much energy is prevented from being absorbed into the middle ear at each frequency or the impedance of the system (Keefe & Simmons, 2003). Greater overall impedance results in lower PA (or higher PR) at the specific frequency assessed.  PA varies as a function frequency and depends on how the acoustic impedance of the middle ear varies with frequency. It is important to note that for frequencies below 800 Hz, impedance is due mostly to stiffness-based reactance (which is 10 times larger than resistance) resulting in only a small proportion of the incident power being absorbed into the middle ear (Puria & Allen, 1998; Allen et al., 2005) At frequencies below 1000 Hz, impedance is due to the stiffness of the tympanic membrane, middle ear volume, and most importantly—the stiffness of the annular ligament (Lynch, Nedzelnitsy, & Peake, 1982). When low frequency pressure waves reach the stapes, almost all of their power is briefly stored as potential energy in the stretched ligament and 2  then returned to the ear canal as a retrograde pressure wave. In other words, an increasing impedance mismatch at the entrance to the middle ear causes most of the acoustic power at frequencies below 1 kHz to be reflected back into the ear canal. At higher frequencies above 6000 Hz, mass-based reactance of the ossicles becomes more important and the overall contribution of reactance is greater than resistance. Between 1 and 5 kHz, stiffness- and mass-based reactance values of the middle ear interact to cancel each other (Allen et al., 2005). As a result, most of the incident acoustic power that reaches the eardrum in the mid-frequency region between 1 and 5 kHz is absorbed into the middle ear and transmitted to the inner ear. This also happens to be the frequency region at which the ear is most sensitive to sound. In summary, at the low- and high-frequency regions the eardrum’s reactance is larger than its resistance, whereas in the mid-frequency region the resistance is larger than the combination of the stiffness- and mass-based reactance.  Due to these properties the overall trend in normative data collected for WAI is consistent with low low-frequency PA, high mid-frequency PA, and low to moderate high-frequency PA values (Margolis et al., 2001; Shahnaz et al., 2009; Margolis, Saly, & Keefe, 1999).    Measures of WAI can be made at ambient or dynamic pressure, allowing flexibility in performing PA measurements of the middle ear as a joint function of frequency and air pressure (Liu et al., 2008). Static pressure (also known as ambient pressure) refers to the pressure that exists within the ear canal when no external forces are applied and dynamic pressures refer to the pressure exerted from either a built-in or external pressure pump, similar to that used in tympanometry (Shaw, 2009).  The current study utilizes systems with built-in and external pressure pumps that change pump speed continuously to perform WAI measurements in a sweep 3  pressure paradigm similar to tympanometry (Interacoustics of America, 2015; Ibraheem, 2014; Liu et al., 2008).    It has been demonstrated that dynamic or pressurized WAI measurements, which obtain acoustic transfer functions (such as PR or PA) as a joint function of frequency and air pressure, reveal more information about middle ear function compared to those performed at ambient pressure alone (Margolis, Saly, & Keefe, 1999; Sanford & Feeney, 2008). This means that when utilizing dynamic pressures, PA measurements can be displayed in the frequency and pressure domain. Margolis, Saly and Keefe (1999) presented a case in which retraction, fibrosis, and atrophy of the tympanic membrane co-existed with negative middle ear pressure. The PA at ambient pressure resembled that of a pressurized normal ear. Consistent with negative middle ear pressure without pathology, 226 Hz tympanometry indicated a TPP of approximately -150 to -250 daPa, normal static acoustic admittance, and tympanometric width. However, otomicroscopy of the ear revealed tympanic membrane retraction, fibrosis, and atrophy, without evidence of middle ear effusion. When the ear canal was pressurized to compensate for middle ear pressure (near -250 daPa), an abnormal PA pattern was revealed when plotted in the pressure domain consistent with pathologic middle ear changes in addition to middle ear pressure. The authors concluded that in the presence of significant middle ear pressure, it may be necessary to compensate by varying ear canal pressure in order to detect additional middle ear pathology. This is an example of pressurized WAI measurements providing more diagnostic information than those made at ambient pressure. Additionally, Sanford and Feeney (2008) found absorbance measurements made under pressurized ear canal conditions in 4, 12, and 24 week infants reflected age related maturational effects. Keefe and Simmons (2003) obtained data on a sample of 42 normal 4  functioning ears and 18 ears with conductive hearing loss. They found that for a fixed specificity of 0.90, the sensitivity in detecting conductive hearing loss was 0.28 for static admittance (using 226 Hz tympanometry), 0.72 for transmittance at ambient pressures, and 0.94 for pressurized transmittance measurements.  1.2 Effect of Gender Margolis, Saly, and Keefe (1999) found that relative to females, males had less stiffness dominated ear drums and greater middle ear resistance for frequencies below 1 kHz, but had less resistance between 2- and 4 kHz. Werner, Levi and Keefe (2010) report that reactance magnitudes at low frequencies (below 600 Hz) and resistance magnitudes were greater for females than males, but there was no effect of gender on PA in their sample of infants 2-9 mo of age and adults. Beers et al. (2010) found no gender related differences in PA measurements using the Mimosa Acoustics device at ambient pressure in children (mean age 6.15 years). Hunter et al. (2008) also found no gender related differences in PA in infants and children (birth to 47 months) using the Mimosa RMS-IV measurement system. A cross-sectional study on healthy neonates and infants aged 1, 2, 4, and 6 months found no gender related differences in PA measurements made at ambient pressure (Athial, Kei, & Driscoll, 2014). Keefe et al. (2000) found PA values below 2000 Hz were lower in males compared to female neonates likely due to the finding that female ears were stiffer than male ears acoustically in this age group. Pooled data from the studies by Shahnaz and Bork (2006) and Shaw (2009) using a sample of 186 Chinese and Caucasian young adults aged 18 – 38 years obtained at ambient pressure with the Mimosa Acoustics system revealed that the interaction between frequency and gender was significant (Shahnaz et al., 2013). Specifically, it was found that females had higher PA than males at the 5  mid-frequencies between 4000 - 5000 Hz. Feeney et al. (2014) who tested a sample of 112 adults aged 23.9 – 51.4 years at ambient pressure also demonstrated a pattern of lower mean PA at frequencies less than the minimum at 3000 Hz and higher mean PA at and greater than this frequency in female participants compared to males. Rosowski et al. (2012) who tested a sample of 29 adults aged 22–64 years at ambient pressure demonstrated significantly higher mean PA at 4 kHz in female participants compared to males. Feeney and Sanford (2004) tested a sample of 40 young adults with a mean age of 21.4 years and 30 older adults with a mean age of 71.6 years at ambient pressure; the researchers found that female young adults had significantly lower PA than males in the low frequencies at 794 and 1000 Hz, but higher PA at 5040 Hz. There was a trend toward lower PA at low- to mid-frequency regions and higher PA at 4000 Hz in elderly females compared to males, but this didn’t reach significance. Kenny (2011) reported that the interaction between gender, frequency, and ethnicity was significant for PA obtained at ambient pressure using the ReflWin system.  Specifically, it was found that Chinese females had higher PA than males at the mid-frequencies between 4000 - 5000 Hz, but this difference was not found in the Caucasian group. Kenny (2011) also reported that the interaction between frequency and gender was significant for all ethnicities when PA measurements were obtained at peak pressure (using the ReflWin) with female participants having higher PA than males at 5000 Hz. A relatively recent study by Polat et al. (2015) on a sample of Turkish young adults aged 18.3 – 26.2 years also found that females had significantly higher PA than males in the mid- to high- frequency range from 3100 Hz to 6900 Hz using the Titan Interacoustics system at ambient pressure. For the most part, it seems that significant differences in mean PA values are observed in the mid-high frequency range for adults, but not necessarily for children or infants.   6  1.3 Effect of Ethnicity Chinese young adults have been demonstrated to have lower low-frequency PA and higher mid- to high-frequency PA compared to Caucasians (Shahnaz & Bork, 2006; Shaw, 2009). Shahnaz and Bork (2006) found that the Chinese group had lower low-frequency PA values between 469 – 1500 Hz and higher mid- to high-frequency PA values between 3891 – 6000 Hz compared to the Caucasian group. Similarly, Shaw (2009) found that PA values for Chinese young adults were lower than Caucasians for frequencies at and below 1250 Hz, similar between 1600 and 3150 Hz, and higher between 4000 and 6000 Hz. Interestingly, they also found that that PA profiles of Caucasian young adults had two distinct minima (at frequencies of 1250 and 3150 Hz) while the Chinese had only one distinct minimum at 3150 Hz. The differences in PA patterns between these groups have been attributed to the variation in size and mechano-acoustical properties of the middle ear such as mobility and thickness of the tympanic membrane or mass of the ossicles. The size of the ear canal and/or middle ear can be indicated by measurements related to body size such as weight, height and circumference of the head. As proposed by Shahnaz and Bork (2006), the larger body sizes in the Caucasian sample may have meant that this sample had larger ear canal volumes and middle ear volumes, which is associated with a decrease in stiffness of the air in the middle ear space and a lower resonance frequency. This in turn could boost low frequency absorbance in the Caucasian group in comparison to the Chinese sample. It was also suggested by Shahnaz and Bork (2006) that larger body sizes in the Caucasian group could be associated with an increase in size of middle ear structures (e.g. area of the tympanic membrane, mass of ossicles, footplate), which in turn could increase the mass of the middle ear system (Werner et al., 1998; Werner & Igic, 2002; Jayesh et al., 2014). An increase in mass of the middle ear system could explain the degradation of high-frequency 7  absorbance of the middle ear in the Caucasian group compared to the Chinese group (Shahnaz & Bork, 2006; Allen et al., 2005; Relkin, 1988; Saunders et al., 1998).   1.4 Effect of Instrument Several researchers have shown that normative data for WAI measurements vary by instrument (Kenny, 2011; Shahnaz, Feeney, and Schairershow, 2013; Shaw, 2009). For instance, Shaw (2009) found that PA measurements made using the Reflwin Intercoustics system for ambient pressures were significantly higher at frequencies below 2000 Hz than those obtained using the Mimosa Acoustics HearID system; Kenny (2011) found that Caucasian participants measured using the Reflwin Interacoustics device had significantly higher estimates of PA from those measured using the Mimosa Acoustics HearID device at 5 kHz, while Chinese participants did not show a difference. The researchers attributed these differences between instruments to different protocols used to calibrate these devices. Specifically, the estimation of ear canal area and differences in the type of probe tip used to seal the ear canal. However, the observed differences between these systems are much smaller than the variance observed among groups with different middle ear pathologies in other literature for these instruments (Feeney et al., 2003; Shahnaz & Bork, 2006; Shahnaz et al., 2009).      Calibration of the probe tip using both the Mimosa Acoustics systems uses four cavities of various known volumes. Proper calibration is dependent on the quality of the probe tip and the level of noise in the room (Hunter & Shahnaz, 2014). The input acoustic admittance of the middle ear (Ym) is calculated as follows (Withnell, Jeng, Waldvogel, Morgenstein & Allen, 2009): 8   Ym  = Us / Pm – Ys  Where Us is the velocity of the sound source (determined during calibration). Pm and Ys (obtained directly during the measurement within the ear canal) are the sound pressure of the microphone source and admittance of the source, respectively.  Ym is related to PR through the following equation:  Ym     =     1 – Rm Yo             1 + Rm  Where Yo  = A/ ρc and A is the cross-sectional area of the ear canal, ρ is the density of air in the ear canal, and c is the speed of sound. ρ and c are constants, but A is estimated based on the probe tip selected on the computer when the measurement is made. Thus, measurements of WAI  rely on the assumption that impedance at the ear drum is similar to that at the microphone, and the cross-sectional area in all participants who use a specific probe tip size are approximately the same (Feeney, Grant & Marryott, 2003).  During calibration, a foam ear tip is placed into four cavities with a diameter of 0.74 cm and two measurements of the pressure response are made within each cavity (Voss & Allen, 1994). The pressure response is plotted with respect to the noise floor for each frequency. The sound pressure of the sound source and acoustic impedance at the source are calculated at each frequency to determine Us (velocity of the sound source). The calibration procedure is verified 9  by turning the cavity back to the first position where the computer determines the mean square error for each of the two measurements made in the four cavities (Hunter & Shahnaz, 2014).   Calibration of the Reflwin Interacoustics system is similar to that of the Titan Interacoustics system. It is done by making measurements in two tubes of specified lengths; the computer then compares the data related to wave characteristics from both tubes and makes a chi-square calculation to determine statistical compatibility (Reflwin Interacoustics, 2008). The diameter of the tube is 0.794 cm, which is slightly larger than the estimation of ear canal diameter (0.74 cm) made by the Mimosa systems (Keefe & Simmons, 2003; Voss & Allen, 1994). Calibration is successful when the chi- square value is close to 1 and RMS is approximately 0.00. In this method, PR is calculated using the following equation:  Q (f) [1 + R(f)]  = P(f) 1 – R(f) x Ro(f)    The Q(f) and Ro(f), which refer to the Fourier transform of the incident sound pressure wave and pressure at the probe respectively, are calculated during calibration. P(f), which is the recorded sound-pressure response, is calculated in the subject’s ear. Taken together, these values allow for the calculation of PR through the following equation:  /R(f)/2 = PR  10  The objective of the current study is to collect normative WAI data from Chinese and Caucasian young adults (aged 18-34) of both genders using four widely available wideband reflectance instruments (Mimosa Acoustics HearID, Otostat Mimosa Acoustics, Titan Interacoustics and Reflwin Interacoustics). If significant differences in normative data between ethnicities, genders and/or instruments are found, it will facilitate further investigation to determine if these differences are larger than the differences observed in various diseased groups as compared to normal groups. If they are not, instrument, gender or ethnicity specific norms may not be necessary to detect middle ear pathology when using WAI.   1.5 Effect of Ear Canal Pressurization on Power Absorbance Measurements WAI measurements can be taken at ambient pressure, which is the static pressure present in the ear canal when no external forces are applied (Shahnaz, Longridge, & Bell, 2009). Dynamic pressure measurements can also be made in which the pressure in the ear canal is varied in a manner identical to tympanometry (Keefe & Levi, 1996).   At ambient pressures, typical adults reveal a WAI pattern consistent with low absorbance in the low frequencies which increases to a maximum between 1000 Hz and 4000 Hz prior to decreasing in the high frequencies (Shahnaz and Bork, 2006; Shaver, 2004). However, when PA measurements are obtained at peak tympanometric pressure (TPP) an increase in low-frequency absorbance and decrease in high-frequency absorbance just above the resonance frequency (1121 Hz) is observed (Margolis, Saly and Keefe, 1999). These changes are consistent with an increase in stiffness of the middle ear due to pressurization (Margolis, Saly and Keefe, 1999).   11  Liu et al. (2008) had expected that EA values would be similar when measured at either TPP or static pressure, given that their sample’s mean TPP was within one standard deviation of ambient pressure. However, they found that PA values at TPP were higher than at ambient pressure in the low frequencies and slightly lower at high frequencies.  Shaw (2009) similarly found higher PA values at dynamic pressures as compared to static pressure in the low frequencies. Burdiek and Sun (2014) reported lower PA values at ambient pressure compared to TPP below 1.5 kHz. Liu et al. (2008) suggest that residual positive pressure present in the external ear canal prior to the ambient measurement state (due to the compression of air when the probe tip is inserted into the ear) could explain the observed differences. The residual pressure could have been avoided by providing ventilation in the probe or setting the pressure back to zero using the pressure pump prior to ambient pressure measurements. However, the presence of this discrepancy would not affect clinical utility of either mode, as these effects would be shared by both healthy and pathological ears.   Kenny (2011) reported significantly lower estimates of PA in both Caucasian and Chinese participants at low frequencies while measuring at ambient pressure compared to TPP. Additionally, they reported that Caucasian participants demonstrated slightly higher estimates of power absorbance using the static method of measurement from 4000 to 5000 Hz. Similarly, Shaw (2009) found that both Chinese and Caucasian young adults showed an increase in the mean PA values overall when dynamic pressures were used instead of static pressure. PA values overall were even higher in the Caucasian group compared to the Chinese group during dynamic pressure measurements.   12  In summary, most studies have shown that PA values are higher in the low frequencies and lower in the high frequencies when measurements were made at TPP in comparison to ambient pressure (Liu et al., 2008; Margolis et al., 1999; Keefe & Simmons, 2003; Sanford & Feeney, 2008).  1.6 Test-Retest Reliability of PA Measurements Vanderwarff, Georgantas, and Prieve (2007) evaluated test-retest variability in a sample of infants (N=127) and adults (N=10). WAI measurements were made with the probe left in place in the ear canal between the first and second tests, and reinserted in the third test. They found that test-retest reliability was excellent in adults with differences being less than or equal to 0.05 PA units across frequencies whether the probe was reinserted between tests or not. For most infants, they found that test-retest differences were small (close to 0.1), particularly when repeated measures were made with the probe in place and only slightly larger when the probe was reinserted between measures. The poorest test-retest performance in infants was found for the lowest (below 500 Hz) and highest frequencies (above 4000 Hz), while test-retest differences were smallest for the mid-frequency range. There was also greater test-retest variability in the frequencies above 2000 Hz in the infants, but these were minimized for the higher frequencies when the probe was kept in place between tests. According to the authors, some factors affecting test-retest performance included environmental noise, subject state, time available for testing, and ear canal size. Ear canal size was mentioned due to the fact that differences in ear canal size may have contributed to probe fit issues, differences in calibration, and differences in estimation of ear canal diameter resulting in variable PA estimates. Much of the variability in PA 13  measurements for the lowest and highest frequencies in these infants may have been related to how well the probe fit in the ear.   Beers et al. (2010) also evaluated test-retest reliability in a subset of their subjects in order to determine the proportion of observed differences due to probe reinsertion compared to those attributed to middle ear effusion. The differences following reinsertion was insignificant compared to the large changes in PA introduced by the presence of effusion in the middle ear. Beers et al. (2010) indicated that test-retest variability was likely due to the fit of the probe in the ear canal.  Werner et al. (2010) measured the test-retest reliability of PA measurements in 183 adults aged 18–30 years. Absolute test-retest correlations for tests conducted approximately 2 weeks apart ranged from 0.95 (at 364 Hz) to 0.28 (at 5823 Hz) and were lowest in the high frequencies compared to the middle and low frequencies. The absolute test-retest differences in PA increased significantly after 3688 Hz and were smaller in the mid-frequency range than at higher frequencies. The authors stated that both test-retest correlations and absolute differences in PA indicated greater stability of WAI transfer functions in the middle frequencies.   Feeney et al. (2014) conducted WAI tests annually (ranging from one to five years) in 112 normal hearing adults (between 27.7 – 45.9 years). They found that individual patterns of PA stayed stable over multiple tests and test-retest variance was about 0.1 at 1000, 2000, and 4000 Hz. This study was in good agreement with Rosowki et al. (2012) who made four weekly PA measurements on seven adults and found that the standard deviation for those measurements was 14  also about 0.1 at 1.0, 2.0 and 4.0 kHz. Rosowski et al. (2012) noted that their mean differences and corresponding standard deviations in PA measurements were not so different from that of the normal population. Feeney et al. (2014) was also in agreement with Werner et al. (2010) who reported that the mean absolute test-retest difference between two PA measurements obtained a week apart in adults was approximately 0.1. Feeney et al. (2014) state that this suggests that the test-retest measurements at these frequencies should fall within + 0.1 PA units about 70% of the time. On source of variability in repeated PA measurements was attributed to small acoustic leaks between the foam ear tip and the ear canal in their study. They suggested that this might be overcome by using an impedance probe tip to obtain a hermetic seal as is done for tympanometry.   Hunter et al. (2008) analyzed test-retest variability of PA measurements in children 3 days to 47 months of age (N=97) using the Mimosa Acoustics RMS-IV system by making sequential measurements within the same test session and reinserting the foam probe tip. The intra-class correlation coefficient was found to be significant and high across all nine frequencies ranging from 0.68 to 0.97. Thus, the authors found evidence of “good reliability” of repeated measures within the same test session.    Voss et al. (2008) made WAI measurements in nine human cadaver ears to investigate the effect of ear canal cross-sectional area (estimated or assumed) at the measurement location, the distance of probe to the tympanic membrane (TM), and middle ear cavity volume on the calculation of PA. They found that all these variables affected PA calculations to some extent. However, middle ear cavity volume had the largest impact on PA measurements (below 1000 Hz 15  and in the high frequencies due to the resonance effects of the entire volume of the middle ear and the geometry of the middle ear); the middle ear cavity volume was deemed to be the only factor (out of the three) contributing substantially to test-retest variations clinically. None the less, it is interesting to note that the study did find that PA increased slightly at frequencies below 5000 Hz and largely above this point as measurement positions moved further from the TM. Also, that PA measurements made with a constant fixed cross-sectional area estimate of 0.43 cm3 compared to those measured (either acoustically or using cross-sections of a silicone based mold) differed only somewhat. Practically speaking, the authors state that this means that the assumptions that diagnostic tests need not control for measurement location and can use a constant cross-sectional area to estimate PA are valid. The authors note that their conclusions about ‘clinical significance’ of cross-sectional ear canal area estimates on PA were made on a sample of only 9 human cadaver ears. It is quite possible that cross-sectional area estimates might vary largely and significantly in a larger sample size causing greater variation in PA measurements between systems, genders, and ethnicities. Indeed, Keefe et al. (1993) found that changes in ear canal area or ear canal diameter (but not ear canal length) over development translated to equally large changes in characteristic impedance of the ear canal such that the impedance of their normal hearing participants at 1 month of age was nearly six fold larger than that of the adults. According to the equation in section 1.1., impedance is indirectly proportional to PA indicating that higher estimates of ear canal diameters would lead to lower values of impedance and higher PA especially at low frequencies where stiffness makes a significant contribution to impedance (Allen et al., 2005).  16  A review by Voss et al. (2013) stated that some additional factors causing test-retest variability include changes in ear canal static pressure or fluid levels between tests. In addition, the orientation of the probe in the ear canal (e.g. blocked against the canal, bent or twisted) can also lead to variations. They conclude that most studies have found that test-retest differences in PA are smaller for adult ears than infant ears.   1.7 Wideband Tympanometry Instead of performing tympanometry at traditional frequencies (e.g. the resonance frequency or at 1000 Hz.), a wideband tympanogram can be obtained in which the average power absorbance between a range of frequencies and pressures is instantaneously measured. Unlike pressurized WAI measurements which display PA three dimensionally as a function of frequency and pressure, wideband tympanometry (WT) displays frequency-averaged PA between 375 – 2000 Hz as a function of pressure level which is swept from 200 to -450 daPa at a rate of 200 daPa/s (the pump speed). The resulting output resembles the conventional two dimensional triangular shaped tympanogram with the exception that it is a calculation of impedance of the middle ear between 375 – 2000 Hz and not admittance at the eardrum using 226 Hz alone. WT is less influenced by noise and offers more reliable information than traditional 226 Hz tympanometry in adults and 1000 Hz tympanometry in infants (Titan Interacoustics, 2013). Particularly for infants, WAI tests (including WT) has been shown to be more accurate at predicting middle ear status when an OAE screening has resulted in a refer result compared to 1000 Hz tympanometry (Sanford et al., 2009). Keefe and Simmons (2003) found WAI tests (ambient and tympanometric) had better test performance compared with 226 Hz tympanometry in predicting conductive hearing loss in young children suspected of having otitis media with effusion.  17  Sanford et al. (2009) recommend considering the implementation of the wideband technologies in the follow-up diagnostics of neonatal screening programs.   Some Clinicians are apprehensive about the use of newer middle ear assessment technologies such as multi-frequency tympanometry because the Vanhuyse model of tympanometric shapes are more difficult to interpret in a busy clinical setting compared to the classic model proposed by Liden (1969) and Jerger (1970) for 226 Hz and 1000 Hz tympanometry. Wideband tympanometry (WT) is a promising new alternative as it may potentially be easy to interpret (given that it has been shown to produce single peaked tympanograms up to 2000 Hz), less influenced by noise, and offer more predictive value in identifying conductive disorders than traditional 226 Hz tympanometry in adults and 1000 Hz tympanometry in infants (Titan Interacoustics, 2013; Sanford et al., 2009; Keefe & Simmons, 2003; Pikorski et al., 1999).  WT using frequency-averaged PA (from 375 – 2000 Hz) may also potentially be interpreted using the model proposed by Jerger (1970) since it can be set to instantaneously measure impedance (unlike multi-frequency tympanometry) at a wide range of frequencies below 1000 Hz at which impedance is due to the stiffness of the tympanic membrane, middle ear volume, and the annular ligament (Allen et al., 2005) creating single peaked tympanograms (Sanford & Feeney, 2008).   However, research needs to be done to determine its utility in identifying specific types of middle ear pathology in different age groups using the model proposed by Jerger (1970). There have been very few published studies on WT thus far due to the technological constraints and questions regarding analysis techniques (Sanford et al., 2013). However, WT data collection has only recently evolved from mathematical calculations of power-based response functions to a 18  hand-held device (Keefe & Simmons, 2003; Sanford et al., 2013). Currently, 226 Hz tympanometry is being utilized clinically to assess middle ear status in adults. However, this probe tone was preferred and standardized because the current day microphones were nonlinear at high frequencies and the probe tone level could be increased without eliciting an acoustic reflex during tympanometry at that time (Shanks & Shohet, 2014). The selection of 226 Hz tympanometry was made without any consideration of its diagnostic value in evaluating middle-ear function (Shanks & Shohet, 2014).  A seminal study on WT by Liu et al. (2008) conducted on 92 adult ears with normal hearing aimed at developing a clinically useful system for the measurement of wideband aural acoustic transfer functions (particularly PA) under tympanometric conditions at a bandwidth of 0.38 – 2 kHz. They noted that this tympanometric bandwidth is preliminary and may be adjusted as more is known about WT in ears with middle ear pathology. The upper limit of 2 kHz was selected in their study because single-peaked PA tympanograms remained present at least up to this frequency in adults. A lower limit of 0.38 kHz was chosen because physiological noise is higher at low frequencies (where SNR for a click stimulus is relatively low). In addition, tympanometric changes in PA are larger at and above 0.38 kHz as opposed to below it. The authors found that their wideband absorbance tympanograms measured using sweep-pressure paradigms were similar to those measured using a sequence of fixed static pressures (Margolis et al., 1999; Keefe & Simmons, 2003; Sanford & Feeney, 2008).  Their results are depicted in Figure 1 below. They plotted frequency-averaged (0.38-2 kHz) PA as a function of air pressure noting that there is a practical advantage to reducing the two-dimensional PA tympanograms to a smaller number of one-dimensional functions, but it is unknown whether significant diagnostic information is 19  thereby lost. Their sweep-pressure technique with feedback control allowed for a shorter measurement duration time which is advantageous for clinical applications. In summary, this study demonstrated that wideband frequency-averaged PA tympanograms had single pressure peaks in normal hearing adults at least up to 2 kHz, allowing for greater ease of interpretation compared to multi-frequency tympanometry.   Figure 1 A depiction of the frequency averaged PA (between 0.38 – 2 kHz) as a function of air pressure. Each panel shows the results at a different sweep speed and direction. The traces show responses from individual ears (N=92). Reprinted with permission from Liu, Y., Sanford, C.A., Ellison, J.C., Fitzpatrick, D.F., Gorga, M.P., & Keefe, D.H. (2008). Wideband absorbance tympanometry using pressure sweeps: system development and results on adults with normal hearing. J. Acoust Soc. Am., 124, 3708–3719. Copyright 2008, Acoustic Society of America.    The tympanograms obtained by Sanford and Feeney (2008) were all single peaked functions at frequencies of 250 Hz, 500 Hz, 1000 Hz, and 4000 Hz with the exception of 2000 Hz. The frequency region where admittance notching is observed in adults is consistent with previous 20  research, showing that the 10th – 90th percentile range for adult middle ear resonant frequency is between 0.8 – 2 kHz (Margolis & Goycoolea, 1993). It is interesting to note that the admittance magnitude tympanograms obtained by Sanford and Feeney (2008) for 12 – 24 week old infants (N=40) were similar in morphology to adult admittance magnitude tympanograms with respect to the absence of notching up to 2000 Hz. However, their admittance magnitude tympanograms for 4-week old infants (N=20) exhibited single peaked tympanograms at 250 Hz and 1000 Hz, but not 500 Hz consistent with infant admittance tympanometry patterns. The admittance magnitude tympanometry patterns in infants was suggestive of canal-wall resonance in the low frequency region which is related to the more compliant nature of the infant ear-canal wall, mass characteristics of the middle ear (e.g. tympanic membrane and ossicles), and changes in ear-canal diameter (Sanford & Feeney, 2008; Alaerts, Luts, & Wouters, 2007).   The current study will obtain normative data in a sample of young adults (using the Titan) to facilitate further research on the clinical utility of WT in assessing middle ear function. This is the first study to collect normative data for WT using the Titan Interacoustics system while taking the effect of ear, gender, and ethnicity into account.  1.8 Other Variables Measured in the Study 1.8.1 Body Mass Index and Equivalent Ear Canal Volume Although body size indices have been correlated to the size of the ear canal, middle ear volume, area of TM, and stapes footplate in animal models, this has not been shown to be the case in human models (Werner et al., 1998; Werner & Igic, 2002). However, a study by Jayesh et al. (2014) demonstrated differences in mean height, width, and length of the stapes between various 21  groups including India and Turkey which could potentially be due to differences in body size. In addition, the average volume of the adult middle ear cavity is 1.5 times larger than that of infants under 1 year of age (Ikui et al., 2000). Adult humans have a canal length between 25 and 27 mm (Shaw, 1978), while newborns have at approximate ear canal length of 22.5 mm (McLellan & Webb, 1957). Thus, it may be reasonable to assume that ear canal size and middle ear volume are correlated to body size in humans.   Shahnaz and Bork (2006) did find that ear canal volumes (calculated using 226 Hz tympanometry) were larger in the Caucasian group compared to the Chinese group, but that observed differences in PA between the Caucasian and Chinese individuals may not have been entirely related to differences observed in their ear canal volumes (ECV).  The authors stated that it would be worthwhile for future studies to calculate ECV using different methods in order to further assess its possible contribution to PA patterns in different ethnic groups. However, indirect estimations of body size (made by comparing PA values of Chinese males and Caucasians females) led to the conclusion that part of the difference in low-frequency PA values between ethnicities was due to body size.   It is important to note that the study by Shahnaz and Bork (2006) compared PA patterns of Caucasian females to Chinese males in order to test the hypothesis that the differences in these two groups could be attributed to body size. Although, they did find that the PA values were comparable in these two groups, this comparison was made based on published data about height and weight from large-scale studies about Caucasian and Chinese participants. The authors mentioned that body size indices were not measured directly and future studies should measure 22  them in order to better establish a correlation between body size and observed differences between people of different ethnicities. The current study directly measured body size using calculations of body mass index (BMI) and ECV estimates from WAI measurements made by four systems. Groups with higher body sizes indicated by higher BMI and ECV values (e.g. Cauacasian and male) were expected to have higher middle ear volumes leading to decreases in the stiffness of the air in their middle ear cavities and higher low-frequency PA (Relkin, 1988). Groups with higher body sizes were also expected to have heavier conductive mechanisms (in terms of size of middle ear structures, area of tympanic membrane, ossicles etc.) which would potentially degrade high-frequency PA responses of the middle ear (Relkin, 1988; Saunders et al., 1998). If these indicators of body size are good correlates of middle ear volume and ear canal size, they were expected to co-vary with observed differences in PA between ethnicities and genders.  1.8.2 Static Acoustic Admittance Peak compensated static admittance (Ytm) is the measurement of the admittance of the middle ear system. It is derived from the subtracting the calculated admittance of the external ear canal from the measurement of the admittance of the probe tone through the ear canal and middle ear system medial to the probe (Fowler and Shanks, 2002). In clinical tympanometry, Ytm is defined as the difference in admittance magnitude at TPP and the admittance magnitude at the most positive static pressure (Keefe & Simmons, 2003).   When ASHA (1990) specified norms were used in a clinical study in Hong Kong up to 48% of Chinese children at various ages failing tympanometric screening were found misdiagnosed for 23  middle ear pathology (Wan & Wong, 2002). This underscored the importance of utilizing the appropriate norms for a specific population in a clinical setting. Norms for Ytm using 226 Hz tympanometry have been shown to vary by gender, ethnicity, as well as several other factors including age (Roup et al., 1998; Wan & Wong, 2002; Shahnaz & Bork, 2006; Shaw, 2009).  These studies have generally found that Ytm is much lower in the Chinese and female groups as compared to the Caucasian and male groups. This is due to the fact that the smaller middle ear cavities (associated with the Chinese and female groups) are thought to be less compliant or more stiffness based middle ear transmission systems resulting in lower Ytm values (Wan & Wong, 2002; Kenny, 2011; Shahnaz & Davies, 2006; Shahnaz & Bork, 2006).  Ytm estimates were obtained by the Titan Interacoustics system in the current study to determine whether groups exhibited differences in compliance or stiffness in their middle ear transmission systems. Since stiffness makes its greatest contribution to impedance in the low frequencies (Allen et al., 2005), higher Ytm values were expected to be associated with groups with lower stiffness elements (males and Caucasians)  in their middle ear systems and higher PA especially at low frequencies.    1.8.3 Resonance Frequency Resonance frequency (RF) corresponds to the frequency at which mass and stiffness contribute equally to middle ear admittance (Shahnaz & Bork, 2008). Various pathologies can alter the mass and stiffness characteristics of the middle ear to produce changes in the static immittance function with concomitant shifts in middle ear resonance (Shanks, Wilson, & Cambron, 1993). For instance, stiffness related pathologies such as otosclerosis tends to shift RF to higher frequencies (e.g. above 800 – 1200 Hz) while mass related pathologies such as ossicular 24  discontinuity shift RF to lower frequencies (Shanks, Wilson, & Cambron, 1993). Normative data for RF are necessary to establish because it has implications in identifying mass and stiffness related pathologies (e.g. otosclerosis or otitis media with effusion).   It is generally known that individuals with smaller ear canal volumes (ECV) have higher resonance frequencies. Previous studies have found that the Chinese and female groups tend to have smaller ECVs and higher RFs as compared to Caucasian and male groups (Shahnaz & Davies, 2006; Wan & Wong, 2002; Shahnaz & Bork, 2008; Polat et al., 2015; Shahnaz & Bork, 2008; Wiley et al., 1996). Females also tend to have lower Ytm values indicating a more stiffness dominated middle ear transmission system which could also explain higher RFs compared to males (Shahnaz & Davies, 2006). This study also investigated the effect of gender and ethnicity on normative data for resonance frequency. Given that the acoustic transmission of sound is boosted through means of a sound pressure gain at and adjacent to the resonance frequency of the ear canal and concha (Gerhardt et al., 1987), groups exhibiting higher RFs (e.g. female and Chinese groups) were expected to have higher high-frequency PA values than those exhibiting lower RFs (e.g. male and Caucasian groups).    1.8.4 Tympanometric Peak Pressure Tympanometric peak pressure (TPP) is the pressure at which the point of highest admittance occurs. This point occurs when the pressures on both sides of the tympanic membrane are equal and will shift with fluctuations in middle ear pressure (Harford, 1973). In clinical tympanometry, TPP corresponds to the pressure at which peak acoustic admittance occurs. It is also the pressure at which the maximal mobility of tympanic membrane and optimal absorption of sound energy 25  occurs (Onusko, 2004). In healthy ears, TPP occurs around ambient pressure (Fowler and Shanks, 2002). Some studies have found TPP to be more positive in normative data collected from Chinese groups compared to Caucasian groups (Shahnaz & Davies, 2006; Wan & Wong, 2002). Differences in normative values for TPP in ethnic groups are thought to be related to anatomic variations in Eustachian tube among these groups (Robinsons & Allen, 1984). Robinsons, Allen, and Root (1988) believed that racial differences in the prevalence of middle ear disorders are related to mechanical and anatomical variations allowing the middle ear to drain more readily in certain groups including African-Americans. The same concept has been hypothesized to explain the lower prevalence of otitis media with effusion in Chinese children (Rushton et al., 1997). Significant gender differences in TPP have not generally been found in most studies (Wan & Wong, 2002; Shahnaz & Davies, 2006; Shahnaz & Bork, 2008). Since the middle ear absorbs sound energy optimally at TPP, it was expected that PA measurements made for all groups at TPP would be higher than at ambient pressure. In addition, since pressurizing the ear stiffens the tympanic membrane and stiffness makes its greatest contribution to impedance in the low frequencies (Allen et al., 2005), it was expected that all groups would exhibit higher low-frequency PA at TPP compared to ambient pressure. At frequencies below 1000 Hz, impedance is due to the stiffness of the tympanic membrane, middle ear volume, and most importantly—the stiffness of the annular ligament (Lynch, Nedzelnitsy, & Peake, 1982). Thus, stressing or stiffening the middle ear systems (with pressurization) was expected to increase PA especially at frequencies up to 1000 Hz. Groups with TPPs which were more negative than atmospheric pressure were expected to have slightly stiffened tympanic membranes (Beers et al., 2010) which would lead to higher stiffening or straining of the eardrum 26  with pressurization (Gaihede, 1996) leading to lower low-frequency PA (than groups with less negative TPP) since stiffness impacts the low frequencies.   1.9 Reflectance Phase Angle and Admittance Magnitude 1.9.1 Reflectance Phase Angle  The review by Voss et al. (2013) had emphasized the need for data selection criteria that would identify acoustic leaks and probes that were either blocked or pushed up against the edge of the canal. In addition to ensuring ECV is not negative in the low-frequency range and low-frequency PA is high below 500 Hz, an interesting suggestion included measuring phase angle of impedance. Voss et al. (2013) suggested that phase angle of impedance should be relatively flat with frequency, negative in most cases for frequencies below 500 Hz and impedance magnitudes should be within bounds. However, these bounds were not identified in the review paper and the authors stated that more research had to be done in the area.   The reflectance phase angle provides information about how the wave is propagated in the ear across frequencies (Mimosa Acoustics, 2012). It is the phase of the reflected pressure relative to the incident pressure (Rosowki et al., 2012); it can also be used to estimate the length of time (group delay) it takes the incident wave to travel to the TM, the time associated with the reflected sound from the TM, and the time it takes for the reflected sound to return to the microphone (Rosowski et al., 2012). The phase of the pressure reflectance or reflectance phase angle is sensitive to the distance between the measurement location and the TM (Rosowki et al., 2012). Thus, the reflectance phase angle and magnitude of immittance varies significantly at different locations within the ear canal (Rosowki, Stenfelt, & Lilly, 2013).  27   Rosowski et al. (2012) measured reflectance phase (in degrees) in 29 normal hearing adults (22 – 64 years of age) using the Mimosa Acoustics HearID system. They found that the phase angle tended to decrease from 0 to more negative values as frequency increased from 0 – 6000 Hz.  This was consistent with Voss and Allen (1994) who found that the reflectance phase (in radians normalized by π) measured in 10 normal hearing young adults (ages 18 – 24 years) tended to decrease from 0 to more negative values with increments in frequency from 0 – 15 kHz.   The average group delay estimated across the whole frequency range measured by Rosowki et al. (2012) was approximately 100 µs, suggesting a distance between the TM and the source in the ear canal of about 1.75 cm. However, the averaged phase versus frequency plot was not a linear relationship throughout the whole frequency range. Frequencies below 1.7 kHz and above 3.7 kHz had a somewhat shorter group delay (76 and 98 µs), compared to the group delay calculated between 1.7–3.6 kHz (150 µs) where there was high PA. The longer delay in the mid-frequency region suggested a distance between source and TM of 2.5 cm.   Sanford & Feeney (2008) measured admittance phase measured in degrees at TPP using a Welch Allyn prototype diagnostic middle ear (DME) analyzer system in 20 normal hearing adults (mean age 24.6 years) and one hundred and one infants with normal hearing. They found that admittance phase in adults demonstrated a general negatively directed monotonic shift from stiffness to mass controlled phase as frequency increased from 0.25 to 5 kHz which then shifted toward a positive direction out to 8 kHz. This pattern was similar to that found by Keefe et al. (1993) and Holte et al. (1991); it may be related to ear canal and/or middle ear resonance effects 28  possibly due to the vibration of the ear-canal wall, TM, and/or middle ear characteristics. Increased ear canal wall compliance may partly explain the multiple resonances observed in the infant groups, and the gradual decline of the resonance at 0.5 kHz with increasing age may reflect developmental changes in ear canal compliance properties.    The phase function zero crossing, indicating equal contributions of outer and middle-ear compliance (+ phase) and mass (- phase) components is approximately near 4 kHz in adults and 2 kHz in children (Sanford & Feeney, 2008). However, the larger adult ear canal volume (resulting in increased compliance) and increased middle ear or ear canal stiffness may also be contributing to the high frequency admittance phase zero crossings in adults as compared to children (Sanford & Feeney, 2008). One might be able to generalize from these findings to predict that all groups with higher ear canal volumes (be it Caucasians compared to Chinese or males compared to females) may exhibit higher frequency admittance phase zero crossings.   1.9.2 Admittance magnitude Admittance magnitude (Y) is defined as the reciprocal of impedance (Mimosa Acoustics, 2012). In addition, it can be viewed as the velocity in the ear to a perfect pressure/force source (Mimosa Acoustics, 2012). Shahnaz and Bork (2006) chose admittance magnitude as an outcome variable in their study because it was thought to be comparable to tympanometric admittance.  In a sample of 126 young adults (age 18 – 32 years), they found that mean Y was significantly higher in the Caucasian group than the Chinese group between 211 to 1313 Hz. This was consistent with tympanometric results obtained by Shahnaz and Davies (2006) which demonstrated that mean compensated Ytm values obtained at probe tone frequencies between 226 - 900 Hz were 29  much lower in the Chinese group compared to the Caucasian group and those obtained up to 1120 Hz were much lower in females than males. Overall, Y values were significantly lower in the Chinese group compared to the Caucasian group at lower frequencies in both genders.   Sanford and Feeney (2008) measured admittance magnitude (measured in mmho) in twenty young adults (mean age 24.6 years) and one hundred and one infants with normal hearing. Consistent with Shahnaz and Bork (2006), they found that admittance magnitude increased with increases in frequency up to a maximal point after which it decreased in magnitude in adults; in contrast to this pattern, infants often had smaller admittance magnitudes and multiple peaks. The authors explained that admittance magnitude is affected by immittance qualities of the air space between probe and TM (unlike PA). Therefore, these measurements are sensitive to acoustic leaks, shallow insertions, and some of the absolute admittance differences observed between age groups may have been due to differences in ECVs.  In the current study, Y was expected to be higher in individuals with higher body sizes such as the Caucasian and male group compared to the Chinese and female group (Roup et al., 1998; Wan & Wong, 2002; Shahnaz & Bork, 2006; Kenny, 2011; Shaw, 2009).   1.10 Hypothesis Based on the main purpose of the study and current literature in the area it was hypothesized that: (1) Female young adults would demonstrate significantly higher PA values in the mid-high frequencies at ambient pressure; (2) Chinese young adults would demonstrate lower low-frequency PA and high mid- to high- frequency PA compared to Caucasians at ambient pressure; (3) PA would vary slightly but significantly by device used and using instrument specific norms 30  would not improve the predictive value in identifying a group of surgically confirmed otosclerotic ears; (4) PA values would be significantly higher in the low frequencies and lower in the high frequencies when measurements are made at tympanometric peak pressure compared to ambient pressure; (5) The instrument would exhibit small significant variation in PA between trials in the low and high frequencies, but that this variation would be much smaller than that between normal and otosclerotic ears; (6) Variation in PA between ethnicities and genders would be related to body size and ear canal volume; (7) Frequency-averaged PA between 375 – 2000 Hz would be higher in male and Caucasian subjects compared to female and Chinese subjects; (8) Phase angle would be higher in female and Chinese subjects compared to male and Caucasian subjects in the high frequencies; (9) Admittance magnitude would be higher in male and Caucasian subjects compared to female and Chinese subjects in the low- to mid- frequencies.      31  Chapter 2: Methods  2.1  Sample Group A cross-sectional research study was conducted to collect ethnic, gender and instrument specific normative data for WAI in normal hearing young adults between the ages 18-34 years. A convenience sample of eightyparticipants were recruited through posters around the campus and an advertisement made on a website created by the psychology graduate student council at the University of British Columbia. This age range was chosen because there is a consensus among researchers in the field of WAI (from the Eriksholm Workshop) that developmental norms are needed for children and adults (Feeney et al., 2013). Although older adults and children have been studied to a great extent, there are very few studies done in the age group selected for the current study and a convenience sample can easily be drawn from the University of British Columbia. Approximately twenty participants were assigned to each of the four subject groups (Caucasian-female, Caucasian-male, Chinese-female, and Chinese-male). As previously specified by Shahnaz and Davies (2006), Chinese groups were comprised of immigrants or Canadian-born children of immigrants from mainland China, Hong Kong, and Taiwan without traceable foreign descent (e.g. both grandparents and parents were from mainland China, Hong Kong, or Taiwan). The Caucasian European group was comprised of individuals of non-Hispanic, non-Aboriginal, non-Arab/West Arab, nonblack, and non-East/South/Southeast Asian, with white or light skin and of European descent (Statistics Canada, 2004; Fillipatos et al., 2013; Shriver et al., 1997). Participants were grouped according to their self-reported classification. Refer to Table Chapter 5:A.1 for a summary of the subject pool demographics.  32  2.2  Inclusion Criteria The subject inclusion criteria for the current study were adapted from Shahnaz and Bork (2006). The inclusion criteria included a case history suggestive of normal hearing, pure tone audiometry indicating air conduction thresholds better than 25 dB HL between 250- 8000 Hz and air-bone gap of < 10 dB between 250 – 4000 Hz, a normal Type A 226 Hz tympanometric configuration, no history of head trauma or middle ear disease, no gross eardrum abnormalities or excessive cerumen as documented by otoscopic examination. As part of the inclusion criteria, the participants also underwent screening of ipsilateral reflexes to determine presence of a response (threshold of compliance > 0.02 ml) in response to 500 Hz, 1000 Hz and broadband stimuli presented from 80 dB HL to 100 dB HL in 5 dB increments. To verify the normal condition of the cochlea and the middle ear, participants underwent transient-evoked otoacoustic emission (TEOAE) and distortion product otoacoustic emission (DPOAE) screening to satisfy inclusion criteria. These tests are sensitive to cochlear hearing loss greater than or equal to 30 dB HL. The criteria for achieving a pass result on the TEOAE were: a pass in 4 out of 5 frequency bands and a good signal-to-noise ratio (SNR) in four out of five half octave bands centered at 1, 1.5, 2, 3 and 4 kHz. The criterion for passing these frequency bands was a SNR of 3 dB at 1, 1.5 kHz and 6 dB at 2, 3, and 4 kHz (Norton et al., 2000); For DPOAE the criteria for achieving a pass result are: a pass in 3 out of 4 frequency bands (1, 2, 3 and 4 kHz) with present emissions at an absolute amplitude above -6dB and an SNR of 6dB at 3 or more of the frequency bands with 4 kHz being a mandatory passing frequency (Gorga et al., 1997). It is often easier to obtain a response at 4 kHz in comparison to 1 kHz due to less residual noise and ensuring that participants pass at this frequency allows us to rule out high frequency hearing loss.   33  2.3 Wideband Acoustic Immittance Devices Currently, four wideband reflectance machines are available for research and clinical purposes. These include two hand-held devices (Otostat Mimosa Acoustics and Titan Interacoustics) and two non-portable devices (Reflwin Interacoustics and Mimosa Acoustics HearID). All participants were tested with all four WAI devices in a randomized fashion (for ear and instrument) to minimize order effects in the study. The participants were then tested again in random order to assess test-retest reliability for all four instruments. All wideband acoustic immittance devices were calibrated once daily before use as recommended by the manufacturers.    2.3.1 The Mimosa Acoustics HearID 5.1 + MEPA3 Module (RMS System Version 5.1.2600) The assembly required an IBM compatible laptop computer attached to a USB audio processing unit which was connected to an ER-10C probe system (with foam ear tips for children and adults or rubber tips for infants).  The HearID+MEPA3 instrumentation employed computer-generated stimuli, automated data monitoring, and advanced signal processing for noise and artifact rejection. Measurements were made rapidly and conveniently over a frequency range of 188 to 6012 Hz at ambient pressure only (Mimosa Acoustics Inc., 2012). Once the probe was placed in the patient’s ear, the time for measuring an ear’s power reflectance was typically less than 30 seconds (Mimosa Acoustics Inc., 2012). The measurement relied on determining the pressure frequency responses through a calibration procedure in which the probe was inserted into a four tube calibration chamber. The probe interface cable connected the probe to the PC board and functioned as a pre-amplifier for that probe. WAI measurements were made by combining the thevenian equivalent determined during calibration with the in-the-ear calibration and measurements made when the probe was in the participants’ ears, as discussed earlier. 34    Figure 2 Illustration of the Mimosa Acoustics HearID hardware are depicted. The USB Audio Processing Unit, MEPA Calibration Cavity Set, Etymotic ER10C probe, and a selection of eartips. Reprinted with permission from Mimosa Acoustics, Inc.  The foam ear tips used in the study were compressed carefully using a squeezing and rotating motion in a controlled manner between the thumb and forefinger before deep insertion into the ear.  We used 14A and 14B size foam ear tips for this study and allowed them to expand fully in the ear for approximately 1 minute before making a measurement. This is relevant due to the fact that when an ear tip is selected, it is indicated on the system to give an estimate of the ear canal volume which is used to set the output voltage for the probe speaker in order to reduce the variations in SPL for different sizes (Mimosa Acoustics Inc., 2012). This estimate is used only if the in-the-ear pressure calibration is not active. With an active in-the-ear pressure calibration, the program uses the volume estimate for the sound pressure that is presented during the in-the-ear calibration. This is approximately 60 dB SPL. The eartip selection also gives MEPA3 an estimate of the ear canal diameter. This value is required to compute the normalized impedance from which all other measures are derived. During the in-the-ear calibration procedure, a 1 kHz tone is presented at an estimated 60 dB SPL re artificial ear cavity through the probe transducers 35  (each transducer is calibrated separately). If a stimulus level of approximately 60 dB SPL and a signal-to-noise ratio of 40 dB or greater is obtained, the pressure calibration is accepted and WAI parameters are calculated. Although HearID is capable of using both a chirp and tone stimulus, this study utilized a chirp stimulus during testing. There are advantages to using sine wave stimuli which tests specific frequencies. These include allowing more control over signal-to-noise ratio (important consideration when testing in high background noise such as in newborns) and optimizing diagnostic sensitivity and specificity if specific frequency regions have been identified as indicative of pathology (Hunter et al., 2008). However, for most participants a chirp stimuli is an optimal stimulus to use since it provides a better frequency resolution and is fast to measure (Mimosa Acoustics Inc., 2012; Lapsley, 2013). Hunter al. (2008) found that broadband chirp and frequency specific sine wave stimuli were equivalent for measures of power absorbance. Given that various middle ear pathologies are characterized optimally at different frequencies, a chirp stimulus was used to characterize the immittance properties of the middle ear at a wide range of frequencies in this study. The current study utilized HearID 5.1 + MEPA3 Module (RMS System Version 5.1.2600).  2.3.2 ReflWin Interacoustics (Software Release Version V.3.2.1) ReflWin is a non-portable system which can make WAI measurements at ambient pressure and dynamic pressures. It consisted of an AT235 probe tip with two output transducers, one input transducer and a probe interface cable that was connected to an AT235h audiometer that can change the pressure in a continuous manner within the ear canal for making measurements of WAI tympanometry. The AT235h audiometer was connected to a personal computer by means of an IFC69 cable that enabled communication between the computer and the audiometer. 36    Figure 3 Illustration of the Reflwin Interacoustics WAI system. The assembly includes the AT235h audiometer used for changing the pressure in the ear canal and a probe tip (bottom right) which is connected to a PC. Reprinted with permission from ReflWin Interacoustics, Inc.   WAI measurements required a calibration procedure in which the waveform responses obtained in two plastic tubes with lengths of 295 cm and 8.4 cm were obtained, as discussed earlier. The waveform characteristics obtained within these two tubes were compared in order to determine the Fourier transform of the incident sound-pressure wave [Q(f)] and the SPL spectra within the tubes were also compared in order to determine the pressure reflectance of the probe [R0(f)]. These measurements were then combined with those made when the probe was in the subject’s ear canal in order to calculate WAI parameters. ReflWin utilizes a zero-phase frequency weighted click stimulus calibrated to 100 dB SPL for patients over 6 months of age during 37  testing. The stimulus rate of the click was approximately 21.5 Hz. The current study utilized ReflWin Interacoustics (Software Version V.3.2.1)  2.3.3 Titan Interacoustics (OtoAccess Version V.1.2.1) A handheld device which allowed viewing traditional tympanograms; it also allowed to view power absorbance as a function of frequency (from 226-8000 Hz) and pressure. It included endless airflow, pressure control technology, high resolution recordings, and an intelligent built in pump system with an adaptive speed control around the tympanic peak (Interacoustics of America, 2015). It can be customized for screening, diagnostic and advanced clinical testing. The Titan is capable of performing impedance testing, auditory brainstem response testing (ABR), otoacoustic emission testing and WAI testing. It can be set to measure high frequency and conventional tympanometry, acoustic reflexes, TEOAE, DPOAE and WAI. In addition, it has a built in pressure pump which can be utilized to conduct WAI tympanometry. Similar to the Reflwin, its measurement of PA relies on a calibration procedure requiring the insertion of a rubber probe tip into two tubes and a direct measurement in the subject’s ear canal. The Titan utilized a zero-phase frequency weighted click stimulus at a rate of 21.5 Hz that flattened the response of the incident wave of the probe. The click was calibrated to 100 dB peSPL for patients over 6 months of age. The current study utilized Tian Interacoustics (OtoAccess Version V.1.2.1).  38   Figure 4 Illustration of the Titan Interacoustics system. The handheld unit can be used independently or while connected to the PC. Reprinted with permission from Interacoustics, Inc.  2.3.4 The Otostat Mimosa Acoustics (Software Version 1.1.9591) A portable, touch-screen, battery powered, handheld screener and diagnostic unit (Mimosa Acoustics, 2013). It employs computer-generated stimuli, automated data monitoring, and advanced signal processing for noise and artifact rejection. Measurements are made rapidly and conveniently at ambient pressure only. Once the probe is placed in the patient’s ear, the time for measuring an ear’s power reflectance is less than 10 seconds (Mimosa Acoustics, 2013). It tests wideband acoustic immittance (MEPA reflectance and absorbance) and measures DPOAEs. The assembly includes a hand held unit (with graphical user interface on the touch-sensitive screen), probe, eartips, calibration cavity set (calibrator), power adaptor, USB cable and support software. The etymotic ER 10-C probe contains two loudspeakers and a microphone to deliver and record sounds in the ear canal. Two disposable foam ear tips of various sizes (14B, 14A) identical to those used by the Mimosa HearID device were used in this study to seal the subject’s ear. The Otostat has an internal rechargeable battery that lasts for about 5 hours and the power adaptor is used to charge this battery. The USB cable connects the Otostat to a computer, which is 39  necessary for probe calibration and test management. Similar to the Mimosa Acoustics HearID instrument, WAI measurements with this device require calibration of the probe tips in a 4 cylinder cavity chamber in addition to measurements made when the probe is in the subject’s ear.   Figure 5 Hand-held Otostat Mimosa Acoustics hand-held unit includes a calibration cavity set, probe, ear tips, USB cable, and power adaptor. Reprinted with permission from Mimosa Acoustics, Inc.  Similar to all the other devices, this instrument employs wideband chirp stimuli, the level of which is not controlled by an in-the-ear calibration like the Mimosa Acoustics HearID MEPA3 system (Mimosa Acoustics, 2013). Instead, the speaker output voltage is based on the eartip used for the test. Smaller eartips are associated with smaller ear canal volumes, so lower speaker voltages are used. The target RMS pressure at the microphone is 60 dB SPL, as measured in an artificial ear (but the true level varies with ear-canal volume). Two measurements are made when the probe is in the ear; the first is displayed as the MEPA result and is also used as the in-the-ear calibration for the first DPOAE stimulus. The second measurement is not displayed and is used only for calibrating the second DPOAE stimulus. Artifact rejection is done for each data block 40  where the instantaneous noise is compared to a threshold in the time domain (Mimosa Acoustics, 2013). The current study utilized Otostat Mimosa Acoustics Software Version 1.1.9591.  2.4 Measurements in the Study Most research in this area collects and analyzes power reflectance or power absorption values as a function of frequency and presents it graphically. Hence, PA is the main outcome variables which was measured in this study at ambient pressure (using the Reflwin Interacoustics and both Mimosa Acoustics instruments) and dynamic pressures (using the Titan interacoutsics and Reflwin Interacoustics). There was a recommendation from the group at the Eriksholm Workshop for future researchers to inspect acoustic impedance measures within groups to determine features that can be used to identify faulty measurements. To this effect, phase angle and admittance magnitude were measured to explore their utility in identifying acoustic leaks. In this study, phase angle was measured by both HearID and ReflWin. Reflectance phase angle provides information about how the wave has propagated in the ear across frequencies (Mimosa Acoustics, 2012). Admittance magnitude was measured by ReflWin and it is defined as the reciprocal of impedance (Mimosa Acoustics, 2012). In addition, it can be viewed as the velocity in the ear to a perfect pressure/force source (Mimosa Acoustics, 2012).   Body mass index as reported by participants was measured in all participants. The equation for body mass index as suggested by Jakobsson et al., 2014 was used for the study:  [Weight (in kg)] / [Height (in m)]2 41   Other variables which were measured in the study include static admittance or compliance (Ytm), resonance frequency (RF), ear canal volume (ECV) and tympanometric peak pressure (TPP). Ytm was measured at 226 Hz by the Titan. It is the peak compensated static acoustic admittance or the compliance value at the peak of the 226 Hz tympanogram when the ear canal volume is compensated for (Interacoustics, 2013). The Titan obtains resonance frequency at peak pressure from WT which calculates frequency-averaged PA between 375 – 2000 Hz (Interacoustics, 2013). The resonance frequency was calculated by the Titan by obtaining the lowest frequency at which the magnitude of the susceptance from the mass is equal to the one from the stiffness (resulting in zero susceptance). Tympanometric peak pressure (TPP) was also measured by the Titan and it was defined as the pressure at which the peak (or highest equivalent volume) was detected (Interacoustics, 2013) Ear canal volume (ECV) was measured by all four WAI devices. ECV is defined as the acoustic admittance estimate of the volume of the ear canal between the probe tip and tympanic membrane (DeBonis & Donohue, 2004). The equivalent ear canal volume in the two MEPA devices was derived from the reflectance group delay measuring phase as a function of frequency (J. L. Miller, personal communication, October 14, 2015). The Titan system measured the equivalent volume at 226 Hz using the susceptance value calculated from the positive tail of pressure sweep (Interacoustics, 2013). The ReflWin calculated ECV from the WAI measurement based on the susceptance (imaginary part of the acoustic admittance) and provided ECV estimates from 250 – 8000 Hz (ReflWin, 2008). The ECV at 250 Hz was extracted from ReflWin to be used in the current study   42  The reflectance area index (RAI) which is expressed in percentage and summarizes reflectance as a function of frequency was measured by HearID (Hunter et al., 2010). RAI is equivalent to the average power reflectance over the (user-defined) specified frequency range of 800 – 5000 Hz (the default range) in the current study (Mimosa Acoustics, 2012). This frequency range can be modified based on user preferences in the software.  Frequency averaged PA was obtained by the Titan during wideband tympanometry in the current study. The Titan Interacoustics device calculates average power absorbance between 375 – 2000 Hz at various pressure levels (daPa) during WAI measurements. This is called wideband tympanometry (WT); the output is what looks like the familiar single peaked tympanogram from positive to negative pressure levels with the exception that the y-axis contains the average PA value between 375 – 2000 Hz.   2.5 Statistical Analysis The ANOVA design was used to analyze the effect of gender, ethnicity, and instrument on wideband acoustic immittance measures; it was also used to assess test-retest reliability. These analyses were performed using Statistica for windows, version 12.   In this model PA was measured using all 4 instruments twice (within-subject factor with two levels) in a repeated measures design to determine test-retest reliability of a given instrument for making WAI measurements. The between-subject factors were incorporated to determine if significant PA measurement differences existed between categories of ethnicity, instrument, ear, and gender. Ear canal volume and body mass index were investigated as possible covariates in the mixed model ANOVA investigating differences in PA measurements between groups. Tympanometric 43  peak pressure, static admittance using 226 Hz tympanometry, and resonance frequency were investigated in univariate tests of significance to determine if they varied significantly between genders, ethnicities, or ears. These three parameters were analyzed due to the fact that they may explain differences in PA measured between various groups. Additionally, the effect of gender, ethnicity, and ear on frequency averaged PA using wideband tympanometry, reflectance phase angle, admittance phase, and admittance magnitude were also investigated using a mixed model ANOVA.   In order to determine if HearID instrument-specific norms are warranted to identify otoslcerotic ears, a receiver operating characteristic (ROC) curve was generated using PA data obtained from all four instruments at 800 and 2000 Hz using normal hearing participants and those with surgically confirmed otosclerosis (Shahnaz et al, 2009) using the HearID system. These frequencies were selected for analysis, because they are points at which the greatest differences in mean PA values occur between normal and pathological ears (See Figure 5.1). These frequencies are also within the range of frequencies found to differ significantly in PA between normal and otoslcerotic ears (Shahnaz et al., 2009; Shahnaz, Longrdige, & Bell, 2009).   An ROC curve is a graph that plots the true positive rate as a function of the false positive rate at different cut-off points (mean PA values in this case). ROC statistical analyses were performed using MedCalc for Windows, version 15.8 (MedCalc Software, Mariakerke, Belgium). The area under the ROC (AUROC) and 95% CI which is the interval in which the true (population) AUROC curve lies with 95% confidence (Hilgers, 1991) was used to conduct this analysis. Interpretation of the AUROC curve for norms at either 800 Hz or 2000 Hz from a particular 44  system is as follows: the area value ranges from 0.5 to 1, where 0.5 indicates that the PA at that frequency (either 800 or 2000 Hz in this case) using normative data for that particular system in order to distinguish between normal and otosclerotic ears is at chance level and 1 indicates perfect test performance. The significance level or p-value is the probability that the observed sample area under the ROC curve is found when in fact the true (population) area under the ROC curve is 0.5. If p is small (p<0.05) then it can be concluded that the area under the ROC curve is significantly different from 0.5 indicating that the test does have the ability to distinguish the normal group from that with the middle ear pathology (Shahnaz, Longridge, & Bell, 2009).     45  Chapter 3: Results   The results section is divided into 4 sections, each of which covers descriptive statistics followed by statistical analysis. These sections include (3.1) The effect of instrument, ethnicity, gender, and ear on PA at ambient pressure; (3.2) The effect of Ambient vs. Peak Pressure on PA between Titan and ReflWin Systems  (3.3) Covariates of Power Absorbance including Body Mass Index and ear-canal volume (3.4). The effect of gender, ethnicity, and ear on tympanometric measures (static admittance, resonance frequency, and tympanometric peak pressure), reflectance phase, admittance magnitude, frequency-averaged PA using wideband tympanometry, and reflectance area index.   3.1 Effect of Instrument, Ethnicity, Gender, and Ear on PA at Ambient Pressure Table 1 shows the descriptive statistics, including mean and standard deviation of PA values obtained with all four WAI instruments at ambient pressure averaged across mean PA values from all two trials, genders, and ethnicities for a total of fifteen frequencies from 250 – 6000 Hz. The average of the mean and standard deviation values for all four devices across frequencies are displayed in the last column.        46   Ambient Pressure  ReflWin Titan HearID  Otostat All Devices Frequency Mean SD Mean SD Mean SD Mean SD Mean SD 250 Hz 0.10	 0.06	 0.12	 0.06	 0.05	 0.07	 0.06	 0.04	 0.08	 0.06	315 Hz 0.09	 0.06	 0.12	 0.07	 0.08	 0.08	 0.08	 0.05	 0.09	 0.07	400 Hz 0.10	 0.08	 0.16	 0.09	 0.12	 0.09	 0.12	 0.07	 0.13	 0.08	500 Hz 0.18	 0.11	 0.24	 0.11	 0.20	 0.11	 0.19	 0.10	 0.20	 0.11	630 Hz 0.27	 0.15	 0.33	 0.14	 0.30	 0.15	 0.30	 0.14	 0.30	 0.15	800 Hz 0.35	 0.18	 0.43	 0.17	 0.39	 0.16	 0.40	 0.16	 0.39	 0.17	1000 Hz 0.43	 0.18	 0.52	 0.16	 0.48	 0.15	 0.49	 0.15	 0.48	 0.16	1250 Hz 0.50	 0.14	 0.59	 0.12	 0.53	 0.14	 0.54	 0.13	 0.54	 0.13	1600 Hz 0.54	 0.14	 0.61	 0.11	 0.57	 0.13	 0.58	 0.13	 0.57	 0.13	2000 Hz 0.58	 0.13	 0.63	 0.12	 0.63	 0.12	 0.63	 0.12	 0.62	 0.13	2500 Hz 0.71	 0.13	 0.72	 0.12	 0.70	 0.12	 0.70	 0.12	 0.71	 0.12	3150 Hz 0.76	 0.13	 0.71	 0.14	 0.74	 0.12	 0.73	 0.12	 0.74	 0.13	4000 Hz 0.74	 0.14	 0.67	 0.17	 0.71	 0.16	 0.71	 0.16	 0.71	 0.16	5000 Hz 0.57	 0.16	 0.52	 0.17	 0.58	 0.22	 0.58	 0.22	 0.56	 0.19	6300 Hz 0.38	 0.14	 0.36	 0.15	 0.45	 0.21	 0.35	 0.20	 0.39	 0.18	8000 Hz 0.36	 0.16	 0.27	 0.18	   0.21	 0.18	 0.28	 0.17	Table 1 Mean and standard deviation of power absorbance values measured at ambient pressure using all four WAI instruments for frequencies between 250 – 8000 Hz averaged across all trials, genders, and ethnicities. Note that HearID doesn’t provide PA measurements at 8000 Hz.   A more detailed version of the descriptive statistics including mean, median, standard deviation, 5th – 95th percentile, maximum, and minimum power absorbance values displayed across frequencies and grouped by trials, gender, ethnicity, and system at ambient and peak tympanometric pressure conditions can be found on Table A.2 in the appendix.  47  Data for the variable PA at ambient pressure was explored using a mixed-model ANOVA. In this model, ethnicity (2 levels), ears (2 levels), and gender (2 levels) served as between subject factors while frequency (15 levels) and instrument used (4 levels including HearID, Otostat, Titan, and ReflWin) served as within subject factors. The resulting design was a 2 x 2 x 2 x 4 x 15 mixed-model ANOVA design, where the first three factors are between-subject factors and the last two are within-subject factors. The results of this ANOVA are summarized in the proceeding section 3.1 of the results and Table Chapter 5:Appendix B  of the appendix.                48  3.1.1 Ethnicity Table 2 and 3 below are descriptive statistics tables for mean and standard deviation of PA values across frequencies from 250 – 8000 Hz based on categories of instrument, ethnicity, and gender.   Power	Absorbance	Chinese	ReflWin	 Titan	 HearID	 Otostat	Gender	 M	 	 F	 	 M	 	 F	 	 M	 	 F	 	 M	 	 F	 	Frequency	(Hz)	M	 SD	 M	 SD	 M	 SD	 M	 SD	 M	 SD	 M	 SD	 M	 SD	 M	 SD	250	 0.10	 0.06	 0.07	 0.03	 0.13	 0.06	 0.08	 0.04	 0.05	 0.03	 0.04	 0.04	 0.06	 0.03	 0.05	 0.05	315	 0.10	 0.06	 0.05	 0.03	 0.13	 0.07	 0.07	 0.04	 0.08	 0.04	 0.07	 0.05	 0.09	 0.05	 0.08	 0.06	400	 0.11	 0.07	 0.06	 0.04	 0.16	 0.09	 0.10	 0.05	 0.12	 0.06	 0.11	 0.07	 0.12	 0.06	 0.11	 0.08	500	 0.18	 0.10	 0.13	 0.06	 0.23	 0.09	 0.16	 0.07	 0.19	 0.09	 0.17	 0.10	 0.19	 0.09	 0.17	 0.11	630	 0.25	 0.12	 0.19	 0.09	 0.32	 0.11	 0.23	 0.10	 0.28	 0.13	 0.25	 0.13	 0.29	 0.13	 0.25	 0.15	800	 0.32	 0.17	 0.28	 0.14	 0.41	 0.14	 0.33	 0.14	 0.37	 0.15	 0.35	 0.15	 0.39	 0.15	 0.37	 0.16	1000	 0.39	 0.17	 0.38	 0.16	 0.51	 0.15	 0.43	 0.16	 0.45	 0.13	 0.45	 0.14	 0.47	 0.13	 0.46	 0.15	1250	 0.48	 0.15	 0.46	 0.13	 0.59	 0.12	 0.52	 0.13	 0.51	 0.11	 0.49	 0.13	 0.52	 0.11	 0.50	 0.12	1600	 0.54	 0.13	 0.51	 0.15	 0.62	 0.09	 0.56	 0.14	 0.56	 0.11	 0.53	 0.15	 0.58	 0.11	 0.54	 0.15	2000	 0.60	 0.13	 0.53	 0.14	 0.66	 0.11	 0.58	 0.14	 0.64	 0.12	 0.59	 0.15	 0.65	 0.12	 0.59	 0.15	2500	 0.73	 0.14	 0.66	 0.13	 0.75	 0.13	 0.67	 0.13	 0.71	 0.12	 0.65	 0.14	 0.72	 0.12	 0.64	 0.14	3150	 0.77	 0.15	 0.75	 0.13	 0.74	 0.16	 0.73	 0.14	 0.74	 0.11	 0.71	 0.14	 0.74	 0.11	 0.70	 0.15	4000	 0.72	 0.16	 0.81	 0.12	 0.67	 0.18	 0.78	 0.12	 0.71	 0.17	 0.75	 0.18	 0.70	 0.17	 0.74	 0.18	5000	 0.58	 0.15	 0.69	 0.12	 0.54	 0.16	 0.64	 0.14	 0.58	 0.22	 0.68	 0.21	 0.58	 0.22	 0.68	 0.21	6300	 0.44	 0.14	 0.46	 0.12	 0.41	 0.15	 0.44	 0.15	 0.47	 0.21	 0.57	 0.19	 0.39	 0.20	 0.47	 0.18	8000	 0.45	 0.15	 0.40	 0.16	 0.36	 0.18	 0.31	 0.17	 	 	 	 	 0.28	 0.21	 0.27	 0.18	Table 2 Mean PA averaged across 2 trials from 250 – 8000 using 4 WAI devices in the Chinese group. Note that HearID doesn’t provide information at 8000 Hz.       49   Power	Absorbance	Caucasian	ReflWin	 Titan	 HearID	 Otostat	Gender	 M	 	 F	 	 M	 	 F	 	 M	 	 F	 	 M	 	 F	 	Frequency	(Hz)	M	 SD	 M	 SD	 M	 SD	 M	 SD	 M	 SD	 M	 SD	 M	 SD	 M	 SD	250	 0.13	 0.07	 0.10	 0.06	 0.14	 0.04	 0.13	 0.06	 0.07	 0.14	 0.04	 0.04	 0.06	 0.04	 0.06	 0.03	315	 0.13	 0.08	 0.10	 0.06	 0.15	 0.06	 0.13	 0.07	 0.10	 0.13	 0.07	 0.05	 0.09	 0.05	 0.09	 0.05	400	 0.15	 0.09	 0.11	 0.07	 0.20	 0.07	 0.16	 0.09	 0.15	 0.13	 0.11	 0.07	 0.14	 0.07	 0.12	 0.06	500	 0.24	 0.13	 0.18	 0.10	 0.29	 0.10	 0.23	 0.09	 0.25	 0.15	 0.18	 0.10	 0.23	 0.11	 0.19	 0.09	630	 0.35	 0.17	 0.25	 0.12	 0.41	 0.13	 0.32	 0.11	 0.37	 0.17	 0.28	 0.13	 0.36	 0.15	 0.29	 0.13	800	 0.43	 0.19	 0.32	 0.17	 0.51	 0.14	 0.41	 0.14	 0.46	 0.18	 0.39	 0.15	 0.45	 0.16	 0.39	 0.15	1000	 0.50	 0.18	 0.39	 0.17	 0.59	 0.12	 0.51	 0.15	 0.52	 0.17	 0.51	 0.16	 0.52	 0.16	 0.47	 0.13	1250	 0.55	 0.14	 0.48	 0.15	 0.63	 0.09	 0.59	 0.12	 0.55	 0.16	 0.58	 0.13	 0.56	 0.15	 0.52	 0.11	1600	 0.58	 0.13	 0.54	 0.13	 0.64	 0.09	 0.62	 0.09	 0.59	 0.13	 0.59	 0.13	 0.59	 0.12	 0.58	 0.11	2000	 0.61	 0.13	 0.60	 0.13	 0.64	 0.10	 0.66	 0.11	 0.64	 0.10	 0.65	 0.12	 0.63	 0.10	 0.65	 0.12	2500	 0.71	 0.12	 0.73	 0.14	 0.71	 0.10	 0.75	 0.13	 0.70	 0.09	 0.75	 0.10	 0.69	 0.09	 0.72	 0.12	3150	 0.74	 0.12	 0.77	 0.15	 0.66	 0.12	 0.74	 0.16	 0.73	 0.10	 0.77	 0.11	 0.73	 0.11		 0.74	 0.11	4000	 0.66	 0.13	 0.72	 0.16	 0.57	 0.15	 0.67	 0.18	 0.67	 0.15	 0.72	 0.14	 0.68	 0.15	 0.70	 0.17	5000	 0.45	 0.11	 0.58	 0.15	 0.41	 0.11	 0.54	 0.16	 0.50	 0.19	 0.55	 0.23	 0.51	 0.20	 0.58	 0.22	6300	 0.34	 0.11	 0.44	 0.14	 0.30	 0.11	 0.41	 0.15	 0.36	 0.17	 0.40	 0.22	 0.27	 0.14	 0.39	 0.20	8000	 0.36	 0.14	 0.45	 0.15	 0.23	 0.16	 0.36	 0.18	 	 	 	 	 0.14	 0.14	 0.28	 0.21	Table 3 Mean PA averaged across 2 trials from 250 – 8000 using 4 WAI devices in the Caucasian group. Note that HearID doesn’t provide information at 8000 Hz.  The main effect of the between-subject factor, ethnicity, was not significant [F (1,149) = 3.31, p = 0.071] indicating that mean PA values (obtained from 226 – 8000 Hz using one-third octave analysis) did not differ significantly by ethnicity collapsed across frequencies at ambient pressure. The interaction between ethnicity and system was also not significant [F (3, 447) = 0.89, p = 0.448] indicating that mean PA values collapsed across frequencies didn’t differ significantly by the system used for measurement at ambient pressure. The main effect of the within-subject factor, frequency, was significant [F (14, 2086) = 989.97, p = 0.000] indicating PA values varied significantly by frequency at ambient pressure. Furthermore, the interaction between frequency and ethnicity was significant [F (14, 2086) = 22.40, p = 0.000] indicating that PA values did differ significantly across frequencies between the two ethnicities at ambient 50  pressure. There was also a significant interaction between system, frequency and ethnicity [F (42, 6258) = 2.45, p = 0.000] indicating that PA measurements differed significantly by frequency and ethnicity across systems at ambient pressure; this interaction is plotted in Figure 6.  Caucasian ChineseFrequency - HzRefWin250400630100016002500400063000.00.10.20.30.40.50.60.70.80.91.0Power Absorbance - PAFrequency - HzHearID25040063010001600250040006300Frequency - HzOtostat25040063010001600250040006300Frequency - HzTitan25040063010001600250040006300Figure 6 Mean PA at ambient pressure displayed in 1/3rd octave intervals from 250 – 6300 Hz is shown for the 2 ethnicities across 4 instruments (ReflWin, HearID, Otostat, and Titan). Vertical bars denote 95% confidence intervals (CIs).     51  To investigate the frequencies at which mean PA values differed significantly by ethnicity in the various WAI instruments, a post-hoc tukey test was performed. Using the ReflWin, Caucasians had higher mean PA values from 630 – 1000 Hz and lower mean PA values from 5000 – 6300 Hz compared to the Chinese. Using HearID, the Caucasians had higher mean PA values from 1000 - 1250 Hz and lower mean PA values from 5000 – 6300 Hz. Using the Otostat, the Caucasians had higher mean PA values at 1250 Hz and lower mean PA values from 5000 – 6300 Hz. Using the Titan, the Caucasians had higher mean PA values from 500 – 1250 Hz and lower mean PA values from 4000 – 6300 Hz. A post-hoc tukey test of the frequency and ethnicity interaction showed that Caucasians had significantly higher mean PA values from the low to mid frequencies (630 – 1250 Hz ) and the Chinese had significantly higher mean PA values in the high frequencies (5000 - 6300 Hz) overall across all devices, genders, and ears. This is depicted in Figure 7 below which shows mean PA values at ambient pressure for Chinese and Caucasian groups collapsed across all devices, genders, and ears. 52   Caucasian Chinese250 400 630 1000 1600 2500 4000 6300Frequency - Hz0.00.10.20.30.40.50.60.70.80.91.0Power Absorbance - PAFigure 7 Mean PA at ambient pressure displayed at 1/3rd octave intervals from 250 – 6300 Hz for the 2 ethnicities collapsed across all devices, genders, and ears. Vertical bars denote 95% CIs.  3.1.2 Gender The main effect of the between-subject factor, gender, was not found to be significant [F (1,149) = 0.17, p = 0.684] indicating that mean PA values (obtained from 226 – 8000 Hz using one-third octave analysis) didn’t differ significantly by gender at ambient pressure. The interaction between gender and system was also not significant [F (3, 447) = 1.99, p = 0.114] indicating that mean PA values didn’t differ significantly between genders and systems at ambient pressure. The interaction between frequency and gender was significant [F (14, 2086) = 7.63, p = 0.000] 53  indicating that PA values did differ significantly by frequency between genders collapsed across all devices, ethnicities, and ears at ambient pressure. There was an interaction between system, frequency, and gender [F (42, 6258) = 2.74, p = 0.000] indicating mean PA values varied significantly by frequency between genders and systems at ambient pressure; this interaction is plotted in Figure 8.    Female MaleFrequency - HzRefWin250400630100016002500400063000.00.10.20.30.40.50.60.70.80.91.0Power Absorbance - PAFrequency - HzHearID25040063010001600250040006300Frequency - HzOtostat25040063010001600250040006300Frequency - HzTitan25040063010001600250040006300Figure 8 Depicts mean PA values at ambient pressure as a function of frequency (in 1/3rd octave intervals) from 250-6300 Hz for the 2 genders across 4 instruments (ReflWin, HearID, Otostat, and Titan). Vertical bars denote 95% CI.   54  Another post-hoc tukey test was performed to determine the frequencies at which mean PA values differed by gender in the various systems at ambient pressure. It was found that mean PA values for females were higher than males in the high frequencies between 4000 – 5000 Hz for both Interacoustic devices (ReflWin and Titan). Albeit not significant, mean PA values were higher in the female group compared to the male group in the higher frequencies using the Mimosa devices (HearID and Otostat). As seen from figure 3, mean PA values varied significantly by gender and frequency for all 4 systems collectively [F (14, 2086) = 7.63, p = 0.000], as well all systems individually (see test-retest reliability analysis below). Mean PA values are plotted by gender and frequency collapsed across all systems, ethnicities, and ears in Figure 9.   55   Female Male250 400 630 1000 1600 2500 4000 6300Frequency - Hz0.00.10.20.30.40.50.60.70.80.91.0Power Absorbance - PAFigure 9 Depicts mean PA at ambient pressure as a function of frequency from 250 – 6300 Hz for the 2 genders collapsed across all devices, ethnicities, and ears. Vertical bars denote 95% CI.  3.1.3 Ear The main effect of the between-subject factor, ear, was not significant [F (1, 149) = 0.05, p = 0.824] indicating that there were no differences in mean PA values (obtained from 226 – 8000 Hz in one-third octave frequencies) between ears at ambient pressure. In addition, the interaction between system and ear used was not significant [F (3, 447) = 1.54, p = 0.204] indicating that mean PA values didn’t differ between systems by ear at ambient pressure. The interaction between frequency and ear was also not significant [F (14, 2086) = 0.72, p = 0.759] indicating 56  that mean PA values didn’t differ significantly between ears across frequencies at ambient pressure. The interaction between frequency, ear, and system was also not significant [F (42, 6258) = 0.58, p = 0.987] indicating that mean PA values didn’t differ significantly between ears and systems across frequencies at ambient pressure.  3.1.4 WAI Instruments The main effect of the within-subject factor of system [ F (3, 447) = 21.48, p = 0.000] was significant indicating that mean PA values varied significantly by the system used for measurement at ambient pressure. The interaction between system and frequency was also significant [F (42, 6258) = 24.77, p = 0.000] indicating that PA values differed between systems across frequencies at ambient pressure. The PA means measured using the four instruments are plotted in Figure 10.   A post-hoc tukey test was performed to determine the frequencies at which the Interacosutics and Mimosa devices differed in PA measurements at ambient pressure. Among the Mimosa Acoustics devices, HearID and Otostat showed significant differences in mean PA measurements at 6300 Hz. Among the Interacoustics devices, Titan and ReflWin showed significant differences in mean PA measurements from 400 - 2000 Hz and 3150 - 5000 Hz.  Mean PA values differed significantly between ReflWin and Otostat at 250 Hz and 800 - 2000 Hz. They also differed significantly between ReflWin and HearID at 250, 630 - 1000, 2000, and 6300 Hz. They differed between Titan and HearID at 250-1600 Hz and 4000 – 6300 Hz. They differed significantly between Titan and Otostat measurements at 250 - 630, 1000 - 1600, and 4000 - 5000 Hz.   57   ReflWin HearID Otostat Titan 250 400 630 1000 1600 2500 4000 6300Frequency - Hz0.00.10.20.30.40.50.60.70.80.91.0Power Absorbance - PAFigure 10 Depicts mean power absorbance (PA) at ambient pressure in 1/3rd octave intervals from 250-6300 Hz for the ReflWin, HearID, Otostat and Titan instruments. Vertical bars denote 95% confidence intervals (CI).   3.1.5 Test-Retest Reliability Table 4 and 5 below display a summary of the mean and standard deviation of PA values at ambient pressure across sixteen frequencies (from 250 – 8000 Hz) in trial one compared to trial two for categories of instrument, gender, and ethnicity.  58   Table 4 Descriptive statistics table including mean and standard deviation of PA measurements obtained from 250 – 8000 Hz (in 1/3 octave frequencies for a total of 16 frequencies) at ambient pressure organized based on categories of instrument, trials, and genders for the Chinese participants.  Trial	1Frequency	(Hz)Mean SD Mean SD Mean SD Mean SD250 0.08 0.03 0.04 0.00 0.06 0.00 0.10 0.02315 0.07 0.02 0.07 0.01 0.08 0.02 0.10 0.02400 0.08 0.01 0.11 0.02 0.12 0.03 0.13 0.03500 0.14 0.04 0.18 0.05 0.17 0.05 0.20 0.07630 0.21 0.07 0.26 0.08 0.26 0.08 0.28 0.10800 0.28 0.07 0.35 0.14 0.36 0.14 0.37 0.101000 0.37 0.10 0.44 0.22 0.45 0.23 0.47 0.181250 0.46 0.21 0.49 0.29 0.50 0.31 0.56 0.311600 0.51 0.28 0.53 0.32 0.55 0.32 0.59 0.352000 0.57 0.34 0.61 0.39 0.62 0.41 0.62 0.382500 0.70 0.46 0.68 0.48 0.68 0.49 0.71 0.503150 0.76 0.51 0.73 0.55 0.72 0.53 0.73 0.494000 0.77 0.48 0.73 0.46 0.72 0.48 0.71 0.435000 0.63 0.39 0.63 0.14 0.63 0.23 0.58 0.336300 0.44 0.23 0.53 0.16 0.43 0.12 0.42 0.178000 0.42 0.22 0.28 0.00 0.33 0.06Trial	2250 0.09 0.03 0.05 0.00 0.06 0.00 0.10 0.03315 0.08 0.02 0.08 0.01 0.09 0.01 0.10 0.02400 0.09 0.01 0.12 0.02 0.12 0.02 0.13 0.03500 0.16 0.05 0.18 0.05 0.19 0.03 0.20 0.06630 0.24 0.07 0.27 0.08 0.28 0.07 0.27 0.10800 0.31 0.08 0.38 0.13 0.39 0.13 0.37 0.141000 0.40 0.11 0.46 0.23 0.48 0.21 0.47 0.211250 0.48 0.23 0.51 0.32 0.51 0.33 0.55 0.321600 0.53 0.31 0.56 0.33 0.57 0.34 0.59 0.362000 0.56 0.32 0.62 0.41 0.63 0.42 0.62 0.352500 0.68 0.48 0.69 0.51 0.69 0.50 0.71 0.483150 0.76 0.54 0.73 0.54 0.72 0.53 0.74 0.524000 0.76 0.50 0.73 0.45 0.72 0.41 0.73 0.465000 0.63 0.42 0.62 0.12 0.63 0.15 0.60 0.346300 0.46 0.25 0.51 0.13 0.42 0.03 0.43 0.158000 0.42 0.21 0.28 0.00 0.35 0.06Power	Absorbance	at	Ambient	Pressure	-	Chinese	GroupReflWin HearID Otostat Titan59   Table 5 Descriptive statistics table including mean and standard deviation of PA measurements obtained from 250 – 8000 Hz (in 1/3 octave frequencies for a total of 16 frequencies) at ambient pressure organized based on categories of instrument, trials, and genders for the Caucasian participants.   3.1.5.1 HearID Data for the variable PA at ambient pressure was explored using a repeated measures mixed-model ANOVA to investigate test-retest reliability. In this model, ethnicity (2 levels), ears (2 levels), and gender (2 levels) served as between-subject factors while frequency (15 levels) and Trial	1Frequency	(Hz)Mean SD Mean SD Mean SD Mean SD250 0.11 0.03 0.05 0.00 0.05 0.01 0.13 0.05315 0.11 0.03 0.08 0.01 0.08 0.02 0.14 0.04400 0.12 0.01 0.13 0.03 0.12 0.04 0.18 0.05500 0.21 0.06 0.22 0.06 0.20 0.07 0.27 0.10630 0.31 0.09 0.33 0.12 0.32 0.13 0.38 0.16800 0.40 0.13 0.43 0.21 0.43 0.22 0.49 0.241000 0.47 0.17 0.51 0.24 0.52 0.25 0.57 0.351250 0.54 0.31 0.56 0.34 0.58 0.35 0.63 0.491600 0.57 0.38 0.59 0.40 0.60 0.38 0.63 0.502000 0.60 0.42 0.64 0.48 0.64 0.47 0.64 0.502500 0.73 0.56 0.72 0.58 0.71 0.56 0.73 0.573150 0.76 0.58 0.75 0.60 0.74 0.57 0.69 0.494000 0.72 0.49 0.69 0.48 0.70 0.48 0.62 0.395000 0.50 0.30 0.52 0.13 0.53 0.18 0.44 0.266300 0.32 0.13 0.39 0.07 0.29 0.04 0.30 0.048000 0.31 0.10 0.14 0.00 0.20 0.00Trial	2250 0.11 0.03 0.05 0.00 0.05 0.00 0.13 0.05315 0.11 0.02 0.08 0.01 0.08 0.02 0.14 0.04400 0.12 0.01 0.13 0.03 0.12 0.03 0.18 0.05500 0.22 0.05 0.21 0.07 0.21 0.06 0.27 0.09630 0.32 0.10 0.32 0.13 0.32 0.13 0.38 0.15800 0.41 0.12 0.42 0.20 0.43 0.21 0.49 0.231000 0.48 0.16 0.51 0.27 0.53 0.28 0.57 0.291250 0.54 0.25 0.56 0.33 0.58 0.37 0.62 0.421600 0.56 0.33 0.59 0.40 0.60 0.41 0.62 0.462000 0.59 0.41 0.65 0.50 0.65 0.51 0.62 0.452500 0.72 0.53 0.73 0.60 0.73 0.60 0.72 0.553150 0.76 0.57 0.76 0.62 0.75 0.62 0.70 0.504000 0.71 0.47 0.71 0.46 0.71 0.47 0.64 0.425000 0.50 0.29 0.53 0.07 0.54 0.13 0.47 0.276300 0.32 0.15 0.38 0.03 0.28 0.03 0.31 0.088000 0.30 0.10 0.13 0.00 0.22 0.00ReflWin HearID Otostat TitanPower	Absorbance	at	Ambient	Pressure	-	Caucasian	Group60  number of trials (2 levels) served as within-subject factors. The resulting design was a 2 x 2 x 2 x 2 x 15 mixed-model ANOVA design, where the first three factors were between-subject factors and the last two were within-subject factors. The ANOVA results are summarized in Table Chapter 5:B.2 of the appendix.   Mean PA values differed significantly between trials [F (1, 155) = 4.05, p = 0.046]. However, mean PA values differed only by approximately 0.005. The interaction between trial number, frequency, and ethnicity was significant [F (14, 2170) = 1.73, p = 0.044]. However, the post-hoc tukey HSD test of this interaction didn’t show any significant differences between trials for any individual ethnicity across frequencies. As established previously, there were differences between ethnicities across frequencies in an individual trial and between trials. The main effect of frequency was significant [F (14, 2170) = 727.23, p = 0.000] indicating that mean PA values varied significantly between frequencies. In addition, the interactions between frequency and gender [F (14, 2170) = 12.02, p = 0.000] and frequency and ethnicity [F (14, 2170) = 3.49, p = 0.000] were significant. As previously established, this indicated that PA values varied significantly by gender and ethnicity across frequencies.    3.1.5.2 Otostat Data for the variable PA at ambient pressure was explored using a repeated measures mixed-model ANOVA. In this model, ethnicity (2 levels), ears (2 levels), and gender (2 levels) served as between-subject factors while frequency (16 levels levels) and number of trials (2 levels) served as within-subject factors. The resulting design was a 2 x 2 x 2 x 2 x 16 mixed-model ANOVA design, where the first three factors were between-subject factors and the last two were 61  within-subject factors. The ANOVA results are summarized in Table Chapter 5:B.3 of the appendix.   Mean PA values differed significantly between trials [F (1, 158) = 9.01, p = 0.003]. However, mean PA values were similar, differing only by approximately 0.007 using the Otostat. All interactions related to trials did not achieve significance. As previously established, the main effect of frequency was significant [F (15, 2370) = 657.15, p = 0.000] indicating mean PA values differed significantly by frequency when using the Otostat system. The interactions between frequency and ethnicity [F (15, 2370) = 13.66, p = 0.000] and frequency and gender [F (15, 2370) = 3.18, p = 0.000] were also significant, indicating that mean PA values differed significantly between genders and ethnicities across frequencies when using the Otostat system for measurements.   3.1.5.3 ReflWin Data for the variable PA at ambient pressure was explored using a repeated measures mixed-model ANOVA. In this model, ethnicity (2 levels), ears (2 levels), and gender (2 levels) served as between-subject factors while frequency (16 levels) and number of trials (2 levels) served as within-subject factors. The resulting design was a 2 x 2 x 2 x 2 x 16 mixed-model ANOVA design, where the first three factors were between-subject factors and the last two were within-subject factors. The ANOVA results are summarized in Table Error! Reference source not found. of the appendix.   62  Mean PA values did not differ significantly between trials [F (1, 150) = 2.03, p = 0.156] when measurements were made using the ReflWin system. All of the interactions related to trial number were not significant, except trial number and frequency [F (15, 2250) = 2.13, p = 0.007]. However, the post-hoc tukey HSD test for this interaction did not reveal any significant differences between trial number 1 and 2 across all frequencies. As established previously, the main effect of frequency was significant [F (15, 2250) = 710.96, p = 0.000] indicating that mean PA measurements made using ReflWin varied significantly between frequencies. The interactions between frequency and gender [F (15, 2250) = 0.19, p = 0.000] and frequency and ethnicity [F (15, 2250) = 0.51, p = 0.000] were also significant as found previously using other systems.   An in depth analysis for test-retest reliability using the ReflWin device at peak pressure can be found in the proceeding section. In summary, it was found that mean PA values didn’t vary significantly between trials at peak pressure.    3.1.5.4 Titan Data for the variable PA at ambient pressure was explored using a repeated measures mixed-model ANOVA. In this model, ethnicity (2 levels), ears (2 levels), and gender (2 levels) served as between-subject factors while frequency (16 levels) and number of trials (2 levels) served as within-subject factors. The resulting design was a 2 x 2 x 2 x 2 x 16 mixed-model ANOVA design, where the first three factors were between-subject factors and the last two were within-subject factors. The results are summarized in Table Chapter 5:B.4 of the appendix.   63  Overall, mean PA values did not differ significantly between trials [F (1, 159) = 0.15, p = 0.698] when measurements were made using the Titan system. The interaction between gender and trial number was significant [F (1, 159) = 6.01, p = 0.011]. However, the post-hoc tukey HSD test revealed no significant differences between trials for both genders. There were also no significant differences in mean PA values between genders in trial one, trial two, and between the two trials.  The interaction between trial number and frequency was significant [F (15, 2385) = 4.57, p = 0.000]. However, the post-hoc tukey HSD test of this interaction revealed that the mean PA values didn’t differ between trial one and two across frequencies except at 5000 Hz, where the PA value during trial number 2 was significantly higher than trial number 1 by approximately 0.020.  As found previously using other systems, the main effect of frequency was significant [F (15, 2385) = 645.04, p = 0.000] indicating that mean PA values differed significantly between frequencies. The interactions between frequency and ethnicity [F (15, 2385) = 29.63, p = 0.000] and frequency and gender [F (15, 2385) = 9.02, p = 0.000] were also significant.   The test-retest reliability using the Titan device at peak pressure can be found in the following section. In summary, it was found that mean PA values varied significantly between trials at peak pressure from 4000 - 6300 Hz in the Titan system.  3.2 Effect of Ambient vs. Peak Pressure on PA between Titan and ReflWin Systems Table 6 below depicts the mean and standard deviation of PA values at ambient and peak tympanometric pressure obtained using both Titan and ReflWin Interacoustics devices across 64  sixteen frequencies (250, 315, 400, 500, 630, 800, 1000, 1250, 1600, 2000, 2500, 3150, 4000, 6300, and 8000 Hz) in 1/3rd octave intervals.   Ambient Pressure Peak Pressure  ReflWin Titan ReflWin Titan Frequency Mean SD Mean SD Mean SD Mean SD 250 Hz 0.10	 0.06	 0.12	 0.06	 0.13	 0.07	 0.13	 0.06	315 Hz 0.09	 0.06	 0.12	 0.07	 0.14	 0.08	 0.13	 0.07	400 Hz 0.10	 0.08	 0.16	 0.09	 0.18	 0.10	 0.18	 0.09	500 Hz 0.18	 0.11	 0.24	 0.11	 0.28	 0.13	 0.26	 0.12	630 Hz 0.27	 0.15	 0.33	 0.14	 0.38	 0.17	 0.36	 0.15	800 Hz 0.35	 0.18	 0.43	 0.17	 0.49	 0.19	 0.46	 0.17	1000 Hz 0.43	 0.18	 0.52	 0.16	 0.57	 0.16	 0.55	 0.15	1250 Hz 0.50	 0.14	 0.59	 0.12	 0.61	 0.12	 0.60	 0.11	1600 Hz 0.54	 0.14	 0.61	 0.11	 0.61	 0.11	 0.61	 0.10	2000 Hz 0.58	 0.13	 0.63	 0.12	 0.62	 0.12	 0.62	 0.12	2500 Hz 0.71	 0.13	 0.72	 0.12	 0.72	 0.12	 0.71	 0.12	3150 Hz 0.76	 0.13	 0.71	 0.14	 0.75	 0.13	 0.70	 0.15	4000 Hz 0.74	 0.14	 0.67	 0.17	 0.69	 0.15	 0.66	 0.18	5000 Hz 0.57	 0.16	 0.52	 0.17	 0.52	 0.16	 0.51	 0.17	6300 Hz 0.38	 0.14	 0.36	 0.15	 0.37	 0.14	 0.36	 0.15	8000 Hz 0.36	 0.16	 0.27	 0.18	 0.36	 0.15	 0.27	 0.18	Table 6 Mean and standard deviation of power absorbance values using two Interacoustics devices (Titan and ReflWin) at both ambient and peak pressure for frequencies between 250 – 8000 Hz averaged across all trials, genders, ears, and ethnicities.  A repeated measures mixed-model ANOVA was used to explore the effect of obtaining PA measurements while pressurizing the ear canal (TPP) as compared to static ambient pressure. In this model, ethnicity (2 levels), ears (2 levels), and gender (2 levels) served as between-subject 65  factors while frequency (16 levels), number of trials (2 levels), pressurization method (2 levels including peak pressure and ambient pressure) and system used (2 levels including Titan and ReflWin) served as within-subject factors. The resulting design was a 2 x 2 x 2 x 2 x 2 x 2 x 16 mixed-model ANOVA design, where the first three factors are between subject factors and the last four are within-subject factors. The ANOVA results are summarized in Table Chapter 5:B.6 of the appendix. The reason that only the analysis was conducted on only the Interacoutsics devices is that only these devices were capable of performing WAI measurements at peak tympanometric pressure.   Overall, mean PA values measured at peak tympanometric pressure (TPP) were significantly higher than at ambient pressure [F (1, 146) = 383.91, p = 0.000]. The interaction of frequency and pressurization method was also significant [F (15, 2190) = 147.05, p = 0.000] indicating that mean PA values differed significantly between peak pressure and ambient pressure across frequencies. Mean PA values at peak pressure were higher than ambient pressure between 250 – 2000 Hz and lower between 3150 – 5000 Hz (see Figure 11).  66   Peak Pressure Ambient Pressure250 400 630 1000 1600 2500 4000 6300Frequency - Hz0.00.10.20.30.40.50.60.70.80.91.0Power Absorbance - PAFigure 11 Mean power absorbance (PA) in 1/3rd octave intervals from 250-8000 Hz is shown across frequencies collapsed across all systems, trial numbers, ethnicities, genders and ears. Vertical bars denote 95% confidence intervals (CI).  3.2.1 The Effect of Gender on PA Measurements at Ambient and Peak Pressure The between-subject factor of gender was significant [F (1, 146) = 4.19, p = 0.043] in that males had significantly higher mean PA values compared to females (0.453 in males compared to 0.432 in females) collapsed across pressurization methods, ears, trials, systems, and ethnicities. The interaction between pressure and gender [F (1, 146) = 4.64, p = 0.033] was significant in that males had higher PA values than females at ambient (0.439 in males and 0.420 in females) and 67  peak pressure (0.467 in males compared to 0.443 in females) individually when collapsed across ears, trials, systems, genders, and ethnicities. The within-subject factor of frequency was significant [F (15, 2190) = 751.98, p = 0.000] indicating that mean PA values varied significantly between frequencies collapsed across systems, pressurization methods, trial numbers, ethnicities, genders, and ears. The interaction between frequency and gender collapsed across systems, pressurization methods, trial numbers, ethnicities, and ears was also significant [F (15, 2190) = 12.52, p = 0.000]. The post-hoc tukey HSD test for this interaction revealed that mean PA values (at ambient and peak pressure combined) were significantly higher in females compared to males in the high frequencies at 4000 - 5000 Hz and lower at 8000 Hz. As seen in Figure 12, although the mean PA values for males were higher than females in the lower frequencies, the differences didn’t attain significance.  68   Female Male250 400 630 1000 1600 2500 4000 6300Frequency - Hz0.00.10.20.30.40.50.60.70.80.91.0Power Absorbance - PAFigure 12 Mean power absorbance (PA) in 1/3rd octave intervals from 250-8000 Hz is shown for the two genders collapsed across all systems, pressurization methods, trial numbers, ethnicities and ears. Vertical bars denote 95% confidence intervals (CI).  The interaction of frequency, gender and pressurization method [F (15, 2190) = 2.44, p = 0.002] was significant and is plotted in Figure 13 below.  The post-hoc tukey HSD test for this interaction revealed that males had significantly higher mean PA values (compared to females) between 500 – 800 Hz and 8000 Hz and significantly lower mean values between 4000 – 5000 Hz when measurements were made at peak pressure. It also revealed that males had higher mean 69  PA values (compared to females) at 8000 Hz and significantly lower mean PA values at 4000 – 5000 Hz when measurements were made at ambient pressure.   Female MaleFrequency - HzPeak Pressure250400630100016002500400063000.00.10.20.30.40.50.60.70.80.91.0Power Absorbance - PAFrequency - HzAmbient Pressure25040063010001600250040006300Figure 13 Mean power absorbance (PA) made at ambient and peak pressure is shown in 1/3rd octave intervals from 250-8000 Hz for the 2 genders collapsed across all systems, trial numbers, and ears. Vertical bars denote 95% confidence intervals (CIs).  Furthermore, the post-hoc tukey also revealed that mean PA measurements made at peak pressure were significantly higher (compared to ambient pressure) between 250 – 1600 Hz and significantly lower between 4000 – 5000 Hz in females. Similarly, in males mean PA values were significantly higher between 250 -1600 Hz and significantly lower between 3150 – 5000 Hz at peak pressure compared to ambient pressure. In females, mean PA measurements at peak pressure were significantly higher between 4000 – 5000 Hz and significantly lower at 8000 Hz 70  compared to males at ambient pressure. Mean PA measurements made at ambient pressure in females were significantly lower between 315 – 1600 Hz and 8000 Hz and significantly higher between 4000 – 5000 Hz than for those made at peak pressure in males.  3.2.2 The Effect of Ethnicity on PA Measurements at Ambient and Peak Pressure The between-subject factor, ethnicity, was not significant [F (1, 146) = 3.05, p = 0.083] indicating that mean PA values didn’t differ significantly between ethnicities collapsed across pressurization modes, systems, genders, and ears. The interaction between pressure and ethnicity [F (1, 146) = 8.51, p = 0.004] was significant indicating that the Caucasian group had higher mean PA values compared to the Chinese group at both peak (0.466 in the Caucasians and 0.444 in Chinese) and ambient pressure (0.436 in the Caucasians and 0.423 in Chinese). The interaction between frequency and ethnicity [F (15, 2190) = 32.38, p = 0.000] was significant. The post-hoc tukey test for the frequency and ethnicity interaction revealed that the Caucasian group had higher mean PA values from 500 - 1250 Hz and lower values between 4000 - 8000 Hz  compared to the Chinese group collapsed across systems, pressurization methods, genders and ears.   The interaction between frequency, pressurization method and ethnicity was also significant [F (15, 2190) = 4.41, p = 0.000] and is plotted in Figure 14. The post-hoc tukey for this interaction revealed that at peak pressure, Caucasians had significantly higher mean PA values between 400 – 1250 Hz and significantly lower values between 4000 – 8000 Hz compared to the Chinese. At ambient pressure, Caucasians had significantly higher mean PA values between 500 – 1250 Hz and lower mean PA values between 4000 – 8000 Hz. Mean PA values for Caucasians at peak 71  pressure were significantly higher from 315 – 1600 Hz and lower between 4000 – 8000 Hz compared to those for the Chinese group at ambient pressure.  Mean PA values for Caucasians at ambient pressure were significantly lower between 5000 – 8000 Hz compared to those for the Chinese group made at peak pressure.   Caucasian ChineseFrequency - HzPeak Pressure250400630100016002500400063000.00.10.20.30.40.50.60.70.80.91.0Power Absorbance - PAFrequency - HzAmbient Pressure25040063010001600250040006300Figure 14 Mean power absorbance (PA) made at ambient and peak pressure is shown in 1/3rd octave intervals from 250-8000 Hz for the 2 ethnicities collapsed across all systems, trial numbers, and ears. Vertical bars denote 95% confidence intervals (CIs).   72  3.2.3 The Effect of Ear on PA Measurements at Ambient and Peak Pressure The main effect of ear [F (1, 146) = 0.51, p = 0.476] was not significant indicating that mean PA values did not differ between ears collapsed across both systems, genders, ethnicities, and trial numbers. The interaction between trial number and ear [F (1,146) = 5.10, p = 0.025] was significant indicating that mean PA values differed significantly between trials and ears. The post-hoc tukey HSD test for this interaction revealed that the differences between the left and right ear between trials and that for the right ear alone between trials were not significant, but the difference between trials for the left ear was significant. However, the PA values measured in trial 1 and trial 2 for the left (0.443 and 0.449 respectively) ear were very similar.  3.2.4 The Effect of System on PA Measurements at Ambient and Peak Pressure The interactions between system and pressurization method [F (1, 146) = 249.50, p = 0.000] and systems, pressurization method, and ethnicity [F (1, 146) = 5.80, p = 0.017] were significant. The post-hoc tukey HSD test of the systems, pressurization method, and ethnicity interaction showed that there were no significant differences in mean PA between ethnicities when tested using the same system (either ReflWin or Titan) and pressurization method (either peak or ambient pressure). It showed that mean PA varied significantly between systems when testing either ethnicity (Chinese or Caucasian) and pressurization method (ambient or peak pressure). It also showed that mean PA varied significantly between pressurization methods in both ethnicities using the ReflWin system, but not the Titan system. The interaction of system and frequency was significant [F (15, 2190) = 36.84, p = 0.000] indicting that mean PA values differed between systems across frequencies.   73  The interaction between system, pressurization method, and frequency was also significant [F (15, 2190) = 66.32, p = 0.000]. This interaction is depicted in Figure 15 and 16. The post-hoc tukey HSD test for this interaction showed that mean PA measurements made using ReflWin were significantly higher at peak pressure than ambient pressure between 250 - 2000 Hz and lower between 4000 - 5000 Hz. It also showed that PA measurements made using Titan was significantly higher from 400 – 1000 Hz at peak pressure compared to ambient pressure. Mean PA values obtained at peak pressure differed significantly between the Titan and ReflWin from 630 - 1000, 3150, 4000, and 8000 Hz. Mean PA values obtained at ambient pressure differed significantly between the Titan and ReflWin systems from 250 - 2000 Hz and 3150 - 8000 Hz.  Figure 10 shows that the mean PA measurements are similar in value using both systems when utilizing peak pressure in comparison to ambient pressure. 74   ReflWin TitanFrequency - HzPeak Pressure250400630100016002500400063000.00.10.20.30.40.50.60.70.80.91.0Power Absorbance - PAFrequency - HzAmbient Pressure25040063010001600250040006300Figure 15 Mean power absorbance (PA) values depicted in 1/3rd octave intervals from 250-8000 Hz obtained at peak pressure and ambient pressure using either the ReflWin or Titan systems.  Vertical bars denote 95% confidence intervals (CI). 75   Peak Pressure Ambient PressureFrequency - HzReflWin250400630100016002500400063000.00.10.20.30.40.50.60.70.80.91.0Power Absorbance - PAFrequency - HzTitan25040063010001600250040006300Figure 16 Mean power absorbance (PA) values depicted in 1/3rd octave intervals from 250-8000 Hz obtained using either the ReflWin or Titan systems at peak pressure and ambient pressure.  Vertical bars denote 95% confidence intervals (CI).  3.2.5 Test-Retest Reliability for Ambient and TPP Measurements The interaction between trial number and frequency collapsed across pressurization methods, genders, ears, systems (ReflWin and Titan), and ethnicities was significant [F (15, 2190) = 3.54, p = 0.000]. However, the post-hoc tukey HSD test for this interaction showed that mean PA values did not differ significantly across all frequencies between trials except 5000 Hz. The interaction between trials, frequency, and ear was significant [F (15, 2190)   = 2.41, p = 0.002]. 76  However, the post-hoc tukey HSD test for this interaction revealed no significant differences in mean PA values between trials for either the left or right ear across frequencies. It also revealed no significant differences in mean PA values between ears for either the first or second trial.  The interaction between system, pressurization method and trial number was significant [F (1, 146) = 4.44, p = 0.036]. The interaction between system, trial number and frequency was also significant [F (15, 2190) = 1.79, p = 0.030] and is plotted in Figure 17.  The interaction between frequency, trial number, pressurization method, and ear was significant [F (15, 2190) = 1.75, p = 0.036]. The post-hoc tukey HSD for this interaction revealed no significant differences in mean PA values between trial 1 and 2 across frequencies at either peak pressure or ambient pressure for the right ear.  Mean PA values significantly differed between trial 1 and 2 at 5000 Hz when calculated at peak pressure and at 500 - 800 Hz and 5000 Hz when calculated at ambient pressure in the left ear.  Mean PA values didn’t differ significantly between ears during trial 1 or trial 2 when obtained at either peak or ambient pressure. Mean PA values differed significantly when obtained at ambient pressure compared to peak pressure during trial 1 and 2 individually in the right ear between 250 - 2000, 4000, and 5000 Hz.  They differed significantly when obtained at ambient pressure in comparison to peak pressure during trial 1 and 2 individually in the left ear between 250 - 1600 and 3150 - 5000 Hz.   The interaction between system, trial number, pressurization method, and frequency was significant [F (15,2190) = 4.03, p = 0.000]. The post-hoc tukey HSD test of this interaction showed that mean PA measurements varied significantly between trials for ambient pressure measurements (not peak pressure) in the ReflWin system at 630 and 800 Hz. It also showed that 77  mean PA values varied significantly between trials for ambient pressure at 5000 Hz and peak pressure at 4000 - 6300 Hz in the Titan system. Mean PA values differed significantly between peak pressure and ambient pressure for ReflWin system in trial 1 and trial 2 individually from 250 - 2000 and 4000 - 5000 Hz. Mean PA values differed significantly between peak pressure and ambient pressure in trial 1 from 400 -1000 Hz and trial 2 between 315 - 1000 and 3150 - 4000 Hz in the Titan system.  Trial 1 Trial 2Frequency - HzReflWin250400630100016002500400063000.00.10.20.30.40.50.60.70.80.9Power Absorbance - PAFrequency - HzTitan25040063010001600250040006300 Figure 17 Mean power absorbance (PA) values depicted in 1/3rd octave intervals from 250-8000 Hz obtained using the ReflWin and Titan systems during trial 1 and trial 2. Vertical bars denote 95% confidence intervals (CI).    78  3.3 Covariates of Power Absorbance 3.3.1 Equivalent Ear Canal Volume  Equivalent ear canal volume (ECV) calculated through WAI measurements using all four instruments were entered as continuous covariates into the original mixed-model ANOVA (investigating PA measurements at ambient pressure) to perform the analysis of covariance (ANCOVA). This compensated for the effect of ECV on PA measurements. The outcome of the statistical analysis, as compared to the analysis performed earlier for the PA at ambient pressure in section 3.1 changed when the effect of ECV was compensated for. Results are summarized in Table Chapter 5:B.7 of the appendix.   When ECV was used as a continuous covariate, the main effect of system or device used was no longer significant [F (3, 420) = 0.124, p = 0.946] in contrast to the original mixed-model ANOVA in which it was. After ECV was compensated for, the main effect of frequency was still significant with a reduced F-value [F (14, 1960) = 131.42 p = 0.000]. The interaction between gender and frequency [F (14, 1960) = 6.24, p = 0.000] and frequency and ethnicity [F (14, 1960) = 11.64, p = 0.000] were also still significant.   After ECV was compensated for, the interaction between system and frequency was still significant with a reduced F- value [F (42, 5880) = 2.84, p = 0.000] as compared to the ANOVA. The interaction between system, frequency, and gender [F (42, 5880) = 1.82, p = 0.001 ] was also still significant with a reduced F-value. A post-hoc tukey of the system, frequency, and genders interaction revealed that all devices showed differences between genders in the high frequencies in contrast to the ANOVA which showed significant differences in only the 79  Interacoustics devices. More specifically, the ANOVA and ANCOVA showed that the Interacoustics devices showed differences at 4000 – 5000 Hz between genders. However, the ANCOVA also showed differences between genders in the HearID device from 5000 – 6300 Hz and in Otostat at 5000 Hz. The interaction between system, frequency, and ethnicity [F (42, 5880) = 1.23, p = 0.146] was no longer significant after ECV was taken into account.   In the ANCOVA, ECV obtained using the ReflWin [F (1, 140) = 11.96, p = 0.001], HearID [F (1, 140) = 8.15, p = 0.005], and Titan [F (1, 140) = 14.57, p = 0.000] systems had a significant effect on mean PA measurements collapsed across all systems, genders, ethnicities, and ears. The interaction between system and ECV measured using ReflWin [F (3, 420) = 14.92, p = 0.000], HearID [F (3, 420) = 3.49, p = 0.016], and Titan [F (3, 420) = 5.43, p = 0.001] was significant indicating that mean PA varied significantly by ECV (measured by the ReflWin, HearID, and Titan). Mean PA values varied significantly by frequency and ECV measured using the ReflWin [F (14, 1960) = 4.59, p = 0.000], HearID [F (14, 1960) = 6.09, p = 0.000], Otostat [F (14, 1960) = 1.70, p = 0.050], and Titan [F (14, 1960) = 4.71, p = 0.000]. The interactions between system, frequency, and ECV using measurements from ReflWin [F (42, 5880) = 12.81, p = 0.000], HearID [F (42, 5880) = 3.09, p = 0.000], Otostat [F (42, 5880) = 2.82, p = 0.000], and Titan [F (42, 5880) = 2.56, p = 0.000] were significant. This indicated that mean PA values differed significantly by frequency depending on system used for measurement and ECV measured by the system.  Data for ECV measured using all 4 systems was also explored using a repeated measures mixed-model ANOVA. In this model, ethnicity (2 levels), ears (2 levels), and gender (2 levels) served 80  as between-subject factors while system or instrument used (4 levels including HearID, Otostat, Titan, and ReflWin) served as within-subject factors. The resulting design was a 2 x 2 x 2 x 4 repeated measures mixed-model ANOVA design, where the first three factors were between-subject factors and the last two were within-subject factors. The results can be summarized in Table Chapter 5:B.8 of the appendix.  The main effect of gender [F (1, 145) = 24.48, p = 0.000] and ethnicity [F (1, 145) = 17.15, p = 0.000] was significant. This meant that males had significantly higher ECV than females (1.20 compared to 1.02 respectively). It also meant that the Caucasian group had significantly higher ECV than the Chinese group (1.19 compared to 1.03 respectively). The main effect of system was significant [F (3, 435) = 62.47, p = 0.000] indicating that mean ECV values differed by system used for measurement. The interaction between system and gender [F (3, 435) = 4.14, p = 0.007] was significant and is plotted in Figure 18 below. The post-hoc tukey HSD test for this interaction revealed that there were significant differences in ear canal volume measurements between males and females for all systems except HearID. In the female group, there were significant differences between ear canal volume measurements made using ReflWin compared to Titan, HearID compared to Titan, and Otostat compared to Titan. In the male group, there were significant differences between ear canal volume measurements made using ReflWin compared to Titan, ReflWin compared to Otostat, ReflWin compared to Titan, HearID compared to Titan, and Otostat compared to Titan. 81    Female MaleReflWin HearID Otostat TitanSystem0.70.80.91.01.11.21.31.41.51.61.71.81.92.0Ear Canal Volume (mmho) Figure 18 Depicts equivalent ear canal volume measured using all 4 systems at a frequency at or near 226 Hz for both genders.  The interaction between system and ethnicity [F (3, 435) = 2.78, p = 0.041] was significant and is plotted in Figure 19 below. The post-hoc tukey HSD test for this interaction revealed that there were significant differences in ECV measured between Chinese and Caucasian groups using HearID and ReflWin. In both the Chinese and Caucasian groups individually, there were significant differences in ECV measurements made using ReflWin compared to HearID, 82  ReflWin compared to Otostat, ReflWin compared to Titan, HearID compared to Titan, and Otostat compared to Titan.   Caucasian ChineseReflWin HearID Otostat TitanSystem0.70.80.91.01.11.21.31.41.51.61.71.81.92.0Ear Canal Volume (mmho) Figure 19 Depicts equivalent ear canal volume measured using all 4 systems at a frequency at or near 226 Hz for both ethnicities.     83  3.3.2 Body Mass Index   Data for BMI was explored using a univariate test of significance. In this model, ethnicity (2 levels), ears (2 levels), and gender (2 levels) served as between-subject factors. The resulting design was a 2 x 2 x 2 x 1 univariate test of significance, where the first three factors were between-subject factors and the last one was a within-subject factor. The results can be summarized in Table B.9 of the appendix.  The analysis revealed that mean BMI of the participant differed significantly by gender [F (1, 160) = 13.76, p = 0.000] and ethnicity [F (1, 160) = 4.15, p = 0.043]. Males had higher BMI than females (23.32 compared to 21.43 respectively) while the Caucasian group had higher BMI than the Chinese group (22.89 compared to 21.85 respectively).   When BMI was compensated for in the ANCOVA, the main effect of system was no longer significant [F (3, 414) = 2.47, p = 0.06]. The main effect of frequency remained significant with a much lower F-value [F (14, 1932) = 24.50, p = 0.000]. The interaction between frequency and gender and frequency and ethnicity remained significant. The interaction between system and frequency [F (42, 5796) = 2.22, p = 0.000] also remained significant, with a much lower F-value. However, a post-hoc tukey of this interaction revealed that mean PA values continued to differ at more or less the same frequencies between systems. The interaction between system, frequency, and gender [F (42, 5796) = 1.82, p = 0.001] and system, frequency, and ethnicity [F (42, 5796) = 2.19, p = 0.000] also remained significant with a slightly reduced F-value (the results are summarized in Table B.10). However, a post-hoc tukey HSD test of the gender, frequency, and system interaction still revealed differences between 4000 – 5000 Hz in both Interacoustic 84  devices indicating that BMI did not account for much of the differences in PA values in these high frequencies. A post-hoc tukey HSD of the ethnicity, frequency, system interaction revealed that when BMI was entered as a continuous covariate, the ethnicities differed between 630 – 1250 and 5000 – 6300 using ReflWin, 5000 – 6300 Hz using both Mimosa devices and 500 – 1000 and 5000 – 6300 Hz using the Titan. In contrast, the ANOVA had showed that ethnicities differed between 630 – 1000 and 5000 – 6300 using ReflWin, 1000 – 1250 and 5000 – 6300 Hz using HearID, 1250 and 5000 – 6300 Hz using Otostat, and 500 – 1000 and 5000 – 6300 Hz using the Titan. This indicates that when BMI was accounted for mean PA values no longer differed at 1000 – 1250 using HearID, 1250 Hz using Otostat, and 1250 and 4000 Hz using the Titan. Interestingly, when BMI was accounted for PA, values started to differ between ethnicities at 1250 Hz using the ReflWin. Overall, it would seem that BMI accounts for much of the differences in mean PA values in the low to mid frequencies (from 1000 – 1250 and 4000 Hz).  3.4 Other Variables The WAI instruments made other measurements which were used to conduct univariate tests of significance and a mixed model ANOVA to explore the effect of ethnicity, ear, and gender on these values. Below (Table 7) are descriptive statistics including mean and standard deviation values of other variables measured in the study including resonance frequency (RF), peak tympanometric peak pressure (TPP), static admittance (Ytm), and reflectance area index (RAI). Refer to A.3 of the appendix for detailed descriptive statistics including mean, standard deviation, 5th – 95th percentile, median, maximum – minimum range, and standard deviation for these parameters.  85    		Caucasian	 Chinese	Male	 Female	 Male	 Female	Mean	 SD	 Mean	 SD	 Mean	 SD	 Mean	 SD	RF	(Hz)	 974.59	 405.39	 933.92	 249.38	 1292.03	 728.15	 1340.59	 891.62	TPP	(daPa)	 -10.65	 13.52	 -3.76	 16.29	 -10.91	 9.30	 -11.03	 11.03	Ytm	(ml)	 0.69	 0.24	 0.51	 0.9	 0.44	 0.16	 0.38	 0.15	RAI	(%)	 59.09	 7.18	 56.33	 6.69	 58.4	 8.24	 58.59	 10.47	Table 7 Descriptive statistics including the mean and standard deviation of parameters including resonance frequency (RF), peak tympanometric peak pressure (TPP), static admittance (Ytm) and reflectance area index (RAI).  3.4.1 Resonance Frequency Data for resonance frequency (RF) was acquired by the Titan system and explored using a univariate test of significance. In this model, ethnicity (2 levels), ears (2 levels), and gender (2 levels) served as between-subject factors while the number of trials (2 levels) served as a within-subject factors. The resulting design was a 2 x 2 x 2 x 2 univariate test of significance, where the first three factors were between-subject factors and the last one was a within-subject factor. The results can be summarized in Table B.11 of the appendix. The univariate analysis revealed that mean resonance frequency measurements using the Titan system differed significantly between ethnicities [F (1, 156) = 16.14, p = 0.000] in that the Chinese group exhibited a higher resonance frequency than the Caucasian group (1312.03 compared to 954.44 respectively). Females exhibited a higher RF than males, but this difference didn’t attain significance (1134.38 compared to 1132.09 Hz respectively).   86  3.4.2 Tympanometric Peak Pressure Tympanometric peak pressure (TPP) was measured using the Titan system and also explored using a univariate test of significance. In this model, ethnicity (2 levels), ears (2 levels), and gender (2 levels) served as between-subject factors while trial numbers (2 levels) served as a within-subject factor. The resulting design was a 2 x 2 x 2 x 2 univariate test of significance, where the first three factors were between-subject factors and the last one was a within-subject factor. The results revealed that TPP differed significantly by ethnicity [F (1, 154) = 4.19, p = 0.042]. This meant that Caucasians had significantly more positive TPP values than the Chinese (-7.12 compared to -10.97 daPa). The results can be summarized in Table B.12 of the appendix.  3.4.3 Static Admittance using 226 Hz Tympanometry Static admittance at 226 Hz (Ytm) was measured using the Titan and explored using a univariate test of significance. In this model, ethnicity (2 levels), ears (2 levels), and gender (2 levels) served as between-subject factors while the number of trials (2 levels) served as a within-subject factor. The resulting design was a 2 x 2 x 2 x 2 univariate test of significance, where the first three factors were between-subject factors and the last one was a within-subject factor. The Chinese had significantly [F (1, 150) = 7.45, p = 0.007] lower Ytm than the Caucasian group (0.59 compared to 0.41). Females had lower Ytm than males (0.56 compared to 0.44) but these differences didn’t attain significance. The results can be summarized in Table B.13 of the appendix.  87  3.4.4 Reflectance Area Index Data for reflectance area index (RAI) was measured using HearID and analyzed using a univariate test of significance. In this model, ethnicity (2 levels), ears (2 levels), and gender (2 levels) served as between-subject factors while the number of trials (2 levels) served as a within-subject factor. The resulting design was a 2 x 2 x 2 x 2 univariate test of significance, where the first three factors were between-subject factors and the last one was a within-subject factor. There were no significant differences in RAI. between genders, ethnicities, or ears. However, males did have higher RAI values compared to females (58.69 compared to 57.47) and the Chinese had higher RAI values than the Caucasians (58.44 compared to 57.72).  RAI differed significantly between trials [F (1, 154) = 5.68, p = 0.018]. The results can be summarized in Table B.14 of the appendix.  3.4.5 Wideband Tympanometry The Titan Interacoustics device calculates average power absorbance between 375 – 2000 Hz at various pressure levels (daPa) during WAI measurements. To evaluate the effects of ethnicity, gender, and ear, a mixed-model ANOVA was performed. The within-subject factor was pressure level (532 levels) from 175 to -356 daPa, and the between-subject factors were gender (2 levels), ethnicity (2 levels), and ear (2 levels). The results are summarized in Table B.15 of the appendix.  The main effect of gender [F (1, 144) = 25.14, p = 0.000] was significant indicating that females had lower mean frequency-averaged PA values compared to males (0.17 and 0.23 respectively). The effect of ethnicity [F (1, 144) = 29.88, p = 0.000] was also significant showing that Caucasians had higher frequency-averaged PA values compared to the Chinese (0.22 and 0.18 88  respectively).  The main effect of pressure was also significant [F (531, 76464) = 1494.98, p = 0.000]. The interactions between pressure and gender [F (531, 76464) = 1.55, p = 0.000] and pressure and ethnicity [F (531, 76464) = 21.03, p = 0.000] were significant; these interactions are plotted in Figure 20 and 21 below. The post-hoc tukey HSD analysis for the pressure and gender interaction revealed that frequency-averaged PA values for males were significantly higher than females between +4 to -74 daPa. The post-hoc tukey HSD analysis for the pressure and ethnicity interaction revealed that frequency-averaged PA values for Caucasians were significantly higher than Chinese between +66 to -70 daPa.   Female Male100 86 72 58 44 30 16 2 -12 -26 -40 -54 -68 -82 -96Pressure - daPa0.100.150.200.250.300.350.400.450.500.550.60Average Power Absorbance - PA Figure 20 Frequency-averaged power absorbance between 375 – 2000 Hz measured by the Titan system is plotted across pressure from +100 to -100 daPa for both genders. Vertical bars represent 0.95 CIs.   89   Caucasian Chinese100 86 72 58 44 30 16 2 -12 -26 -40 -54 -68 -82 -96Pressure - daPa0.10.20.30.40.50.6Average Power Absorbance - PAFigure 21 Frequency-averaged power absorbance averaged between 375 – 2000 Hz measured by the Titan system is plotted across pressure from +100 to -100 daPa for both ethnicities. Vertical bars represent 0.95 CIs.  3.4.6 Admittance magnitude (Y) and Admittance Phase 3.4.6.1 ReflWin 3.4.6.1.1 Admittance Phase  Data for phase angle was analyzed using a repeated measures mixed-model ANOVA. In this model gender (2 levels), ethnicity (2 levels), and ear (2 levels) were between-subject factors. Trial number (2 levels) and frequency (32 levels) were within-subject factors. The resulting 90  design was a 2 x 2 x 2 x 2 x 32 repeated measures mixed-model ANOVA. The results are summarized in Table B.16 of the appendix.   The main effect of ethnicity was significant [F (1, 150) = 32.13, p = 0.000] indicating that the mean reflectance phase angle differed significantly between ethnicities. The effect of frequency was also significant [F (15, 2250) = 1244.48, p = 0.000] indicating that the mean phase angle differed between frequencies. The interactions of frequency and gender [F (15, 2250) = 5.65, p = 0.000] and frequency and ethnicity [F (15, 2250) = 2.03, p = 0.010]  were significant; they are plotted in Figure 22 and 23 respectively. The post-hoc tukey HSD test for the interaction between gender and frequency revealed that females had significantly higher mean phase angle values between 4000-5000 and lower at 8000 Hz compared to males. The interaction of trial number, frequency, and ethnicity was also significant [F (15, 2250) = 3.54, p = 0.000]. The post-hoc tukey HSD test for the interaction between ethnicity, frequency and trial number revealed that the Chinese group had higher mean phase angle values between 4000 – 6300 Hz compared to the Caucasian group during both trial 1 and trial 2 individually.  There were no significant differences in mean phase angle values between trials for either the Chinese or Caucasian group, except at 8000 Hz for the Caucasian group.   91   Female Male250 400 630 1000 1600 2500 4000 6300Frequency - Hz-100-80-60-40-20020406080100Phase Angle - DegFigure 22 Admittance phase in degrees measured by the ReflWin system is plotted from 250 – 8000 Hz for both genders. Vertical bars represent 0.95 CIs. 92   Caucasian Chinese250 400 630 1000 1600 2500 4000 6300Frequency - Hz-100-80-60-40-20020406080100120Phase Angle - DegFigure 23 Admittance phase measured by the ReflWin system (in degrees) is plotted from 250 – 8000 Hz for both ethnicities. Vertical bars represent 0.95 CIs.  3.4.6.1.2 Admittance Magnitude (Y)  Table 8 below shows the descriptive statistics, including mean and standard deviation of admittance magnitude (Y) values obtained with ReflWin across frequencies from 250 – 8000 Hz averaged across two trials. A detailed version of the descriptive statistics including mean, standard deviation, 5th – 95th percentile, median, maximum, and minimum values of Y values across frequencies organized under categories of ethnicity, gender, and trial number can be found in the appendix (A.4).    93   Table 8 descriptive statistics, including mean and standard deviation of admittance magnitude (Y) values obtained with ReflWin across frequencies from 250 – 8000 Hz for categories of ethnicity and gender.  Data for Y between 250 – 8000 Hz extracted from the ReflWin system was analyzed using a repeated measures mixed-model ANOVA. In this model gender (2 levels), ethnicity (2 levels), and ear (2 levels) were between-subject factors. Trial number (2 levels) and frequency (32 levels) were within-subject factors. The resulting design was a 2 x 2 x 2 x 2 x 32 repeated measures mixed-model ANOVA. The results are summarized in Table B.17 of the appendix.   The main effect of gender was significant [F (1, 150) = 26.29, p = 0.000]. This indicated that mean Y was significantly higher in males than females (with a mean of 15.96 compared to 14.46, respectively).  The main effect of ethnicity [F (1, 150) = 5.19, p = 0.024] was also significant. Frequency Mean SD Mean	 SD Mean SD Mean	 SD250 3.65 2.32 1.36 1.99 4.75 2.25 2.95 2.58315 4.52 2.22 2.32 1.98 5.73 2.23 3.84 2.55397 6.99 2.01 4.95 1.82 8.24 2.17 6.38 2.47500 9.23 1.89 7.36 1.79 10.57 2.17 8.70 2.51630 11.17 1.87 9.43 1.83 12.45 2.10 10.65 2.59794 12.74 1.88 11.25 1.92 13.75 1.74 12.08 2.461000 14.07 1.90 12.77 1.64 14.91 1.59 13.22 1.791260 16.06 2.13 14.55 1.48 16.80 1.59 14.78 1.651587 17.71 2.24 16.08 1.61 18.72 1.67 16.19 2.112000 20.48 2.62 17.95 2.29 21.48 1.71 19.12 2.472520 23.70 3.19 21.23 2.59 25.04 2.29 22.21 3.483175 26.74 3.57 25.20 2.78 28.55 3.11 25.36 4.024000 27.05 5.20 26.60 3.77 29.56 3.65 26.43 4.535040 22.71 6.00 24.95 5.40 24.60 4.82 23.24 6.636350 16.71 5.10 18.26 5.81 16.78 4.14 16.76 6.158000 13.77 6.29 13.76 4.10 11.21 5.12 11.69 5.38Chinese	 Caucasian	Male Female Male Female94  This indicated that mean Y was significantly higher in the Caucasian group compared to the Chinese group (15.54 and 14.87, respectively). The effect of frequency was significant [F (15, 2250) = 1314.56, p = 0.000] indicating that Y varied significantly by frequency. The interaction between frequency and gender [F (15, 2250) = 6.45, p = 0.000] and frequency and ethnicity [F (15, 2250) = 6.12, p = 0.000] was significant; they are plotted in Figure 24 and 25 respectively. The post-hoc tukey HSD test for the interaction of frequency and gender revealed that males had higher Y between 250 – 400 Hz and 1600 – 3150 Hz compared to females. The post-hoc tukey HSD test for the interaction of frequency and ethnicity revealed that Caucasians had significantly lower Y at 8000 Hz compared to the Chinese.     95   Female Male250 400 630 1000 1600 2500 4000 6300Frequency - Hz05101520253035Admittance - dB (re: 0 dB for 1 mmho)Figure 24 Admittance magnitude (in dB) obtained by the ReflWin is plotted from 250 – 8000 Hz for both genders. Vertical bars represent 0.95 CIs.  96   Caucasian  Chinese250 400 630 1000 1600 2500 4000 6300FREQUENC05101520253035Admittance - dB (re: 0 dB for 1 mmho)Figure 25 Admittance magnitude (in dB) obtained by the ReflWin system is plotted from 250 – 8000 Hz for both ethnicities. Vertical bars represent 0.95 CIs.  3.4.6.2 HearID  3.4.6.2.1 Reflectance Phase Angle Data for phase angle was analyzed using a repeated measures mixed-model ANOVA. In this model gender (2 levels), ethnicity (2 levels), and ear (2 levels) were between-subject factors. Trial number (2 levels) and frequency (496 levels) were within-subject factors. The resulting design was a 2 x 2 x 2 x 2 x 496 repeated measures mixed-model ANOVA. The results are summarized in Table B.18 of the appendix.  97   The main effect of gender was significant [F (1, 154) = 10.18, p = 0.002] indicating that phase angle varied significantly between genders. The effect of frequency was also significant [F (247, 38038) = 762.07, p = 0.000] indicating that the phase angle varied significantly across frequencies. The interaction between frequency and gender was significant [F (247, 38038) = 6.41, p = 0.000]. The post-hoc tukey HSD test for this interaction revealed that mean reflectance phase values for females were significantly higher than males between 5578 – 5602 Hz. The interaction between frequency and ethnicity didn’t attain significance [F (1, 154) = 0.41, p = 0.521]. 98   Female Male258 398 633 1008 1594 2508 4008 6000Frequency - Hz-1.0-0.9-0.8-0.7-0.6-0.5-0.4-0.3-0.2-0.10.0Reflectance Phase - rd/2πFigure 26 Reflectance phase (in rd/2d π) measured by the HearID system is plotted from 258 - 6000 Hz for both genders. Vertical bars represent 0.95 CIs.        99  Chapter 4: Discussion  In order to effectively use WAI in clinical practice, all sources of variability arising from instrument, gender, and ethnicity must be taken into account in order to assess whether group-specific norms result in significant improvements in the detection of middle ear pathology. This study investigated the effect of instrument, gender, and ethnicity on WAI measurements. The main outcome variable was power absorbance (PA) which was measured at both ambient and tympanometric peak pressure for comparison. Other outcome variables included frequency-averaged PA (between 375 – 2000 Hz), reflectance area index (between 800 – 5000 Hz), and admittance magnitude. These other variables were investigated because they have been under represented in the literature and have great potential for use as viable clinical measures for detecting middle ear pathology with relative ease of interpretation. Body mass index, ear canal volume (which were indicative of ear canal size or diameter and middle ear cavity volume), and various tympanometric measures (static acoustic admittance, peak tympanometric pressure, and resonance frequency) were obtained to investigate differences in PA values between various groups. A set of normative data based on gender, instrument, and ethnicity was also created for reflectance phase angle to be used as a potential parameter in detecting acoustic leaks or shallow probe insertion into the ear-canal.   The discussion is divided into 10 sections: (4.1) Summary; (4.2) Possible covariates of power absorbance; (4.3) The effect of ethnicity, gender, and ear on PA at ambient pressure; (4.4) Test-retest reliability for PA measurements at ambient pressure; (4.5) The effect of instrument on PA measurements at ambient pressure; (4.6) The effect of ethnicity, instrument, gender, and ear on 100  ambient vs. peak pressure measurements; (4.7) The effect of gender, instrument, and ethnicity on frequency-averaged PA using wideband Tympanometry; (4.8) Reflectance area index (RAI); (4.9) Reflectance phase angle and admittance magnitude; and (4.10) Limitations and future directions   4.1 Summary Power Absorbance at Ambient Pressure It was found that power absorbance (PA) varied significantly across frequencies. More specifically, PA at ambient pressure (collapsed across all devices, ears, genders, and ethnicities) tended to decrease with decreasing frequency prior to the absorbance maximum at 3150 Hz and decrease with increases in frequency after that. Overall, Caucasians had significantly higher mean PA values from the low to mid frequencies (630 – 1250 Hz) and the Chinese had significantly higher mean PA values in the high frequencies (5000 - 6300 Hz) collapsed across all devices, genders, and ears. Mean PA values for females were significantly higher than males in the high frequencies between 4000 – 5000 Hz for both Interacoustic devices (ReflWin and Titan). Albeit not significant, mean PA values were higher in the female group compared to the male group in the higher frequencies for both the Mimosa Acoustics devices as well (HearID and Otostat). When the effect of equivalent ear canal volume (ECV) was adjusted for, mean PA values for females were higher than males in various higher frequencies ranging from 4000 – 6300 Hz depending on the device used and at 5000 Hz across all devices, ethnicities, and ears. Mean PA values differed significantly between systems across frequencies as documented in the literature previously (Resatshwane & Neely, 2014; Kenny, 2011; Shahnaz, Feeney, & Schairer, 2013; Shaw, 2007); however, these differences were not as great as the differences observed 101  between normal and pathological ears in the current study and in previous literature (Beers et al., 2010; Shahnaz et al., 2009; Rosowski et al., 2012). As demonstrated previously by Shaw (2007), the current study found that HearID instrument specific norms did not improve the predictive value of WAI testing at 800 and 2000 Hz indicating that they are not unequivocally necessary in identifying otosclerosis using the HearID system. However, they may potentially be useful for diagnostic purposes using a larger frequency bin for analysis  in otosclerosis or other cases of middle ear pathology, and using other instruments.   Test-Retest Reliability of Power Absorbance at Ambient and Peak Tympanometric Peak  Pressure Statistical analysis on test-retest reliability showed that mean PA did not vary significantly between trials across frequencies for either of the Mimosa Acoustic systems at either ambient or peak pressure. Mean PA values using the Titan differed slightly but significantly between trials at 5000 Hz using ambient pressure and between 4000 – 6300 Hz at peak pressure. Mean PA values also significantly differed in the Relfwin system at ambient pressure at 630 and 800 Hz. Slight variability between trials is documented in the literature, but the differences between trials are not as large as the differences observed between normal and pathological ears (Vander Werff, Prieve, & Georgantas, 2007; Beers et al., 2010; Shaw, 2009; Burdiek & Sun, 2014; Shaver, 2004; Werner et al., 2010; Feeney et al., 2014; Rosowki et al., 2012). As a result, these tools exhibit good test-retest reliability for diagnostic purposes.     102  PA at Ambient and Peak Tympanometric Pressure Mean PA differed significantly between peak pressure and ambient pressure across frequencies. Mean PA values at peak pressure were higher than ambient pressure between 250 – 2000 Hz and lower between 3150 – 5000 Hz collapsed across all systems, genders, trials, and ears. More specifically, PA measurements made using ReflWin were significantly higher at peak pressure than ambient pressure in the low frequencies (between 250-2000 Hz) and lower in the high frequencies (between 4000-5000 Hz). However, PA measurements made using Titan at peak pressure were significantly higher in the low frequencies (from 400 – 1000 Hz) compared to measurements made at ambient pressure; PA values obtained using the titan at peak pressure were also lower in the high frequencies (between 4000 – 5000 Hz) compared to ambient pressure although not significantly.   Mean PA values obtained at peak pressure differed significantly between the Titan and ReflWin from 630-1000, 3150, 4000, and 8000 Hz. Mean PA values obtained at ambient pressure differed significantly between the Titan and ReflWin systems from 250-2000 Hz and 3150-8000 Hz. Overall, mean PA measurements were more similar in value between the Titan and ReflWin systems when measurements were conducted at peak pressure compared to ambient pressure.   Males had significantly higher mean PA values (compared to females) between 500 – 800 Hz and at 8000 Hz, as well as significantly lower mean PA values compared to females between 4000 – 5000 Hz when measurements were made at peak pressure collapsed across both interacoustic devices. These results are in contrast to measurements made at ambient pressure which only demonstrated a significant difference between genders in the interacoustic devices at 103  high frequencies between 4000 – 5000 Hz (and a trend toward significance in the low frequencies).   At peak pressure, Caucasians had significantly higher mean PA values in the low frequencies (between 400 – 1250 Hz) and significantly lower values in the high frequencies (between 4000 – 8000 Hz) compared to the Chinese when data was collapsed across both systems. These results are similar to the significant differences in PA between ethnicities found at ambient pressure in the low and high frequencies.   Body Mass Index as a Continuous Covariate Mean BMI of the participant differed significantly by gender and ethnicity. Males had higher BMI than females (23.32 compared to 21.43 respectively) while the Caucasian group had higher BMI than the Chinese group (22.89 compared to 21.85 respectively). When BMI was compensated for in the ANCOVA, the main effect of system was no longer significant. The interactions between system, frequency, and gender and system, frequency, and ethnicity remained significant with a slightly reduced F-value compared to the original ANOVA. However, a post-hoc tukey HSD test of the gender, frequency, and system interaction still revealed differences between 4000 – 5000 Hz in both Interacoustic devices indicating that BMI did not account for much of the differences in PA values between genders over this frequency range. When the effect of BMI was adjusted for, mean PA values no longer differed between ethnicities at 1000 – 1250 using HearID, 1250 Hz using Otostat, and 1250 and 4000 Hz using the Titan. This indicated that BMI did explain much of the differences in PA between ethnicities observed in the low to mid frequencies (from 1000 – 1250 and 4000 Hz) in various systems.  104   Ear-Canal Volume as a Continuous Covariate Males had significantly higher ECV than females (1.20 compared to 1.02 respectively). The Caucasian group had significantly higher ECV than the Chinese group (1.19 compared to 1.03 respectively). Mean ECV values differed by system used for measurement. Significant differences in ear canal volume measurements were found between males and females for all systems except HearID. There were also significant differences in ECV measured between Chinese and Caucasian groups using HearID and ReflWin system. When ECV was entered as a continuous covariate, the main effect of device used was no longer significant in contrast to the original mixed-model ANOVA. The interaction between system, frequency, and gender was still significant with a reduced F-value. A post-hoc tukey of the system, frequency, and gender interaction revealed that all devices showed differences between genders in the high frequencies (specifically between 4000 – 5000 Hz in the Interacoustics devices, between 5000 – 6300 Hz in the HearID device, and at 5000 Hz in the Otostat device) in contrast to the ANOVA which only showed differences in the Interacoustics devices (between 4000 – 5000 Hz). This indicated that factors other than ECV may be accounting for differences in PA between genders (in these high frequencies). The interaction between system, frequency, and ethnicity was no longer significant in the ANCOVA as compared to the ANOVA when ECV was taken into account. This indicated that ECV did explain much of the differences in PA between ethnicities in various systems.      105  Tympanometric Measures of Static Admittance, Resonance Frequency, and Tympanometric Peak Pressure Other variables which could explain differences in mean PA between various groups were analyzed using univariate tests of significance. It was found that the Chinese group exhibited a higher resonance frequency (RF) than the Caucasian group (1312.03 Hz compared to 954.44 Hz respectively). Females exhibited a higher RF than males, but this difference was slight and did not attain significance (1134.38 Hz compared to 1132.09 Hz respectively). Caucasians had significantly more positive TPP values than the Chinese (-7.12 compared to -10.97 daPa). However, TPP values in both ethnicities were relatively close to atmospheric pressure (0 daPa). The Chinese had significantly [F (1, 150) = 7.45, p =  0.007] lower Ytm than the Caucasian group (0.59 compared to 0.41). Females had lower Ytm than males (0.56 compared to 0.44) but these differences did not attain significance.  Phase Angle  Admittance phase measurements made using ReflWin (in degrees) decreased with increasing frequency, decreasing sharply after 2500 Hz, and increased from 6300 out to 8000 Hz.  Females had significantly higher admittance phase values between 4000 and 5000 Hz and lower at 8000 Hz compared to males. The Chinese group had higher admittance phase values between 4000 and 6300 Hz compared to the Caucasian group.   Statistical analysis for reflectance phase angle measurements using the HearID (in rd/2pi) revealed that mean phase angle values steadily decreased with increases in frequencies. Mean reflectance phase values for females were significantly higher than males between 5578 – 5602 106  Hz. There were no statistically significant differences in mean reflectance phase values between ethnicities.   Admittance Magnitude Statistical analysis for admittance magnitude (Y) using the ReflWin (in dB: where 0 dB is 1 mmho) revealed that Y values increased with increases in frequency until it reached its maximum at 4000 Hz after which it decreased with increases in frequencies. Males had significantly higher Y between 250 – 400 Hz and 1600 – 3150 Hz compared to females. Caucasians had significantly higher Y at 8000 Hz compared to the Chinese.   Frequency-Averaged PA in Wideband Tympanometry Using wideband tympanometry, it was found that females had lower frequency-averaged PA (between 375 – 2000 Hz) overall compared to males. Caucasians had higher frequency-averaged PA values overall compared to the Chinese. Mean frequency-averaged PA values for males were significantly higher than females between +4 to -74 daPa. Mean frequency-averaged PA values for Caucasians were significantly higher than the Chinese between +66 to -70 daPa.  Reflectance Area Index The reflectance area index (which is the reflectance in % averaged over the range of 500 – 8000 Hz in the current study) or RAI measured by HearID varied significantly between trials by a small amount. However, there were no significant differences in RAI between genders, ethnicities, or ears. 107  4.2 Possible Covariates of Power Absorbance The potential source of differences in PA observed between ethnicities and genders could be explained by BMI and ECV as they may relate to differences in ear canal size, cross-sectional area of the ear canal, and middle ear volume between groups (Shahnaz & Bork, 2006). A study of the middle ears in exotic cat species found that the compliance of the middle ear cavity increases with body size (Huang, Rosowski, & Peake, 2000). This indicates that differences in body size (indicated by BMI and ECV) may also reflect differences in the relative stiffness of the middle ear transmission system. Stiffness makes its greatest contribution to impedance in the low frequencies (Allen et al., 2005).    4.2.1 Body Mass Index Males had significantly higher BMI than females (23.32 compared to 21.43 respectively) while the Caucasian group had significantly higher BMI than the Chinese group (22.89 compared to 21.85 respectively). This is consistent with previous large scale studies which have similarly shown higher BMI in males as compared to females and in Caucasians as compared to the Chinese (Bell et al., 2002; Bulik et al., 2001; Jackson et al., 2002; Rushton, 1992). In the current study, mean BMIs of Caucasian females (22.49), Caucasian males (23.21) and Chinese males (23.41) were more comparable in contrast to Chinese females (20.23).  When BMI was compensated for in the ANCOVA, the main effect of system was no longer significant. This indicates that differences in BMI explained the variation in mean PA values due to different systems used for measurement. Perhaps some of the observed differences in PA estimates between systems may be due to the fact that the Mimosa systems use a sponge probe 108  ear tip which expands to potentially provide a better acoustic seal in ear-canals of variable size or geometry compared to the Interacoustics systems which use a rigid plastic ear tip. This is consistent with Vanderwarff, Prieve, and Georgantas (2007) who included ear canal size as a source of variability in their measurements due to the fact that differences in ear canal sizes may have contributed to probe fit issues, differences in calibration, and differences in estimation of ear canal diameter resulting in variable PA estimates between systems. It is also consistent with Voss et al. (2013) who stated that changes in the orientation of the probe in the ear-canal (e.g. blocked, bent, or twisted) could also result in differences in PA estimates obtained in a sample.    When BMI was accounted for in the ANCOVA, mean PA values continued to differ in the high frequencies between genders in the Interacoustic devices similar to the ANOVA. However, mean PA values no longer differed significantly between ethnicities across systems at low and mid-frequencies. This indicates that BMI accounts for most of the differences in mean PA values between ethnicities in the low to mid frequencies (approximately from 1000 – 1250 and 4000 Hz) in the current study. However, BMI accounted for very little of the differences between genders which occurred in the high frequencies. Shahnaz and Bork (2006) utilized the HearID system which had initially found differences in ethnicities between 469 – 1000 Hz and 3891 – 6000 Hz. However, when the effect of BMI was indirectly adjusted for (by comparing Caucasian females with Chinese males), the differences in PA between ethnicities only remained from 4828 – 6000 Hz. It was concluded that part of the differences in PA at low frequencies (from 469-1000 Hz and 3891 – 4828 Hz) between ethnicities was related to body size. Their results are consistent with the current study which has also demonstrated that BMI accounts for much of the 109  differences in mean PA values between ethnicities in the low and mid frequencies. Similarly, Shahnaz and Davies (2006) demonstrated that controlling for body size (through adjustments for ECV) in ethnicities obliterated differences in static acoustic admittance at low probe tone frequencies (226 Hz), but not high frequencies (560, 630, 710, 800, and 900 Hz). This suggests that body size (indicated by height and weight or ECV) plays a significant role in the  transmission of sound through the middle ear at the low frequencies, but other mechano-acoustical properties of the middle ear may be contributing to differences observed at high frequencies.     Part of the differences in PA at low frequencies between ethnicities have been attributed to differences in body size because it may have resulted in larger ear canal sizes and middle ear volumes in the Caucasian group than in the Chinese group (Shahnaz & Bork, 2006). This in turn is associated with a decrease in stiffness of the air in the middle ear space and a lower resonance frequency which would boost low frequency PA in the Caucasian group in comparison to the Chinese. Another reason that BMI may have contributed to differences in PA between ethnicities could be the fact that it may indicate underlying differences in ear-canal diameter. Keefe et al. (1993) found that changes in ear canal area or ear canal diameter (but not ear canal length) over development translated to equally large changes in characteristic impedance of the ear canal such that the impedance of their normal hearing participants at 1 month of age was nearly six fold larger than that of the adults. It may follow then that the Caucasian group who exhibited larger BMIs also had larger ear canal cross-sectional areas which led to lower estimations of characteristic impedance resulting in lower estimations of PR and higher PA (see equation in section 1.1 which relates PA, cross-sectional area and characteristic impedance) in the low 110  frequencies. It was also suggested that larger body sizes in the Caucasian group could be associated with an increase in size of middle ear structures (e.g. area of the tympanic membrane, mass of ossicles, footplate), which in turn could be associated with an increase in the mass of the middle ear system (Shahnaz and Bork, 2006). An increase in mass of the conductive mechanism or an increase in mass reactance could explain the increase in impedance and degradation of the mid to high frequency PA of the middle ear in the Caucasian group compared to the Chinese group and in males as compared to females (Relkin, 1988; Saunders et al., 1998; Allen et al., 2005). However, BMI has shown to be an inaccurate reflection of body fat (Ode et al., 2007). The mass of the conductive elements of the middle ear might be better indicated by measures of body composition. Calculations of body composition reveal information about the relative proportions of fat and lean mass (referring to bones, tissues, organs, and muscle) in the body (Esmat, 2012). The most accurate and commonly used tools to measure body composition are the bod pod and bioelectrical impedance analysis to measure lean body mass and body fat percentage (Esmat, 2012). Bod pods are fiber glass units that measure body weight and body volume. The bioelectrical impedance analysis assumes that fat contains littler water and most of the body’s water is in the lean compartment; this tool measures the resistance of the current through the body. These calculations are best done with the help of a trained health and fitness professional, so interdisciplinary research is recommended in the future. Alternatively, body fat percentage can be measured by using skinfold calipers.    4.2.2 Ear Canal Volume Overall, males had significantly higher ECV than females (1.20 compared to 1.02 respectively) and the Caucasian group had significantly higher ECV than the Chinese group (1.19 compared to 111  1.03 respectively). This is consistent with previous studies (Polat et al., 2015; Shahnaz & Bork, 2008; Wan & Wong, 2002; Roup et al., 1998).   The ANCOVA revealed that when ECV was compensated for, mean PA values did not differ significantly by system indicating that the differences in calculation of mean PA by various systems were largely influenced by the calculation of ECV between systems (e.g. the volume of air between the probe tip and the tympanic membrane) much as they were by BMI.  Ear canal volume is mathematically related to the cross-sectional area of an ear-canal which is used in the estimation of characteristic impedance of the ear canal and PA (see equation in section 1.1). Thus, it may be that compensating for ECV in the ANCOVA indirectly controlled for variation in the estimation of the cross-sectional area of the ear canal by each system thereby leading to the abolishment of differences in PA by system used for measurement.   When ECV was compensated for, mean PA values no longer varied significantly between ethnicities across low and high frequencies in different systems. This indicated that differences in mean PA measurements between ethnicities across frequencies using different systems were explained by differences in ECV measurements. Higher ECVs in Caucasians may be associated with higher middle ear volumes and lower resonance frequencies in this group which would boost low-frequency PA in Caucasians compared to Chinese groups (Shahnaz and Bork, 2006). Higher ECV in Caucasians may also have indicated higher ear canal diameters resulting in lower estimates of the characteristic impedance of the ear canal and higher PA calculations (Keefe et al., 1993) in the low frequencies. As discussed earlier, ECV is also an indicator of body size which means that the higher ECV in Caucasians may have been associated with higher mass of 112  their conductive mechanism (e.g. area of the tympanic membrane or mass of the ossicles) may potentially explain the degradation of high frequency PA in this group compared to the Chinese.   When ECV was compensated for, significant differences in mean PA by frequency collapsed across systems between genders were attenuated, but did not diminish entirely. This indicated that differences in ECV measurements explained very little of the differences in mean PA measurements between genders across frequencies using different systems. A post-hoc tukey HSD test of this interaction revealed that all devices showed differences between genders in the high frequencies as opposed to the original ANOVA which only indicated differences between genders for the Interacoustics devices. This indicated that factors other than ECV may be accounting for differences in PA between genders (in these high frequencies). These may include differences in head size, circumference of the head in the sagittal and frontal plane, cross-sectional area of the ear canal, ear canal diameter, and ear canal length (Voss et al., 2013; Keefe et al., 1993).   4.3 The Effect of Ethnicity, Gender, and Ear on PA at Ambient Pressure 4.3.1 The Effect of Ethnicity PA varied by frequency in both ethnicities indicating that mean PA values decreased with decreases in frequency prior to the absorbance maximum and decreased with increases in frequency following the maxima. Previous research has shown that normative data does vary by ethnicity (Shahnaz, Feeney, & Schairer, 2013; Beers et al., 2010; Shahnaz & Bork, 2006; Shahnaz & Davies, 2006; Wan & Wong, 2002; Shaw, 2009). This study found that Chinese young adults have lower PA at low frequencies (630 – 1250 Hz range) compared to their 113  Caucasian counterparts and Caucasians have lower PA at high frequencies (5000 – 6300 Hz range) compared to their Chinese counterparts collapsed across all devices, genders, and ears. Similar to the current findings, Shahnaz and Bork (2006) found that the Chinese group had lower PA values than the Caucasians in the low frequencies (between 469 and 1500 Hz) and higher PA values in the high frequencies (between 3891 and 6000 Hz) using the Mimosa HearID device. Kenny (2011) also found that Chinese young adults had lower PA values in the low frequencies (between 800 – 1250 Hz) and higher values in the high frequencies (at 5000 - 8000 Hz) compared to Caucasians using the ReflWin device at peak pressure. In addition, Shaw (2009) found that PA values for Chinese young adults were lower than Caucasians in the low frequencies ( < 1250 Hz), similar in the middle frequencies (between 1600 - 3150 Hz), and higher in the high frequencies (between 4000 - 6000 Hz) when using pooled data from the ReflWin and HearID system at ambient pressure. In summary, the findings of the current study demonstrate that Chinese young adults have significantly lower low-frequency PA and higher high-frequency PA compared to their Caucasian counterparts collapsed across all devices, genders, and ears.  The current study demonstrated an absorbance maximum at 3150 Hz when PA measurements made at ambient pressure are collapsed across all gender, ethnicities, ears, and instruments. This is consistent with previous studies which have found absorbance maximas at 2997 Hz (Shaw, 2009), 3000 Hz (Shahnaz & Bork, 2006), 3200 Hz (Keefe et al. 1993), 3500 Hz (Margolis, Saly, & Keefe, 1999), 3700 Hz (Werner et al., 2010), between 2000 and 4000 Hz (Liu et al., 2008), and 4000 Hz (Burdiek & Sun, 2014; Feeney & Sanford, 2004; Kenny, 2011) in adults. The slight 114  variation in absorbance maxima may be related to factors such as age (Werner et al., 2010) and BMI (Huang, Rosowski and Peake, 2000).   Energy transmission into the middle ear is most efficient at the absorbance maximum (Keefe et al., 1993). The absorbance maximum occurred at a lower frequency in the Caucasian group compared to the Chinese (specifically at 3600 Hz in the Caucasian group and at 4000 Hz in the Chinese) in the current study. A study of middle ears in exotic cat species has demonstrated that the compliance of the middle ear cavity increases with body size while the frequency at which the absorbance maximum occurs decreases with body size (Huang, Rosowski and Peake, 2000). Given that the BMI of Caucasian participants is significantly higher than the Chinese participants in this study (mean of 22.89 compared to 21.85 respectively), a lower absorbance maximum in the Caucasian group in comparison to the Chinese was expected.  Consistent with previous studies, the current study found that the resonance frequency occurs at higher frequencies (mean of 1312.03 compared to 954.44 respectively) in the Chinese group compared to the Caucasian group (Shahnaz & Davies, 2006; Wan & Wong, 2002). Given that the acoustic transmission of sound is boosted through means of a sound pressure gain at and adjacent to the resonance frequency of the ear canal and concha (Gerhardt et al., 1987), a higher resonance frequency in the Chinese group may have also contributed to the higher frequency absorbance maximum and higher PA values in the high frequencies (at 5000 Hz regardless of device used) in this population compared to the Caucasian group due to optimal acoustic transmission. As discussed in section 4.2, a higher BMI in the Caucasian group may have also indicated a larger ear canal size or ear canal volume (mean of 1.19 in the Caucasian group compared to 1.03 in Chinese in the current study) and middle ear volume which is associated with lower stiffness in the air of the 115  middle ear space and lower resonance frequency potentially resulting in higher PA at lower frequencies in this group compared to the Chinese (Shahnaz & Bork, 2006). Higher ear canal volumes in the Caucasian group may have also indicated higher ear canal cross sectional areas at the measurement location of the probe resulting in lower calculations of characteristic impedance of the ear canal and higher estimations of PA in the low frequencies in this group compared to the Chinese (Keefe et al., 1993). Additionally, larger BMIs may be correlated with an increase in mass and size of the conductive elements of the middle ear (e.g. size of ossicle, tympanic membrane etc.) potentially leading to higher mass reactance, impedance, and lower PA in the high frequencies in Caucasian groups (Allen et al., 2005; Shahnaz & Bork, 2006; Werner et al., 1998; Werner & Igic, 2002). Future investigations should investigate indices of body composition including lean body mass to better represent differences in the mass of the conductive mechanism between ethnicities which have been demonstrated thus far (Jayesh et al., 2014).     Ears with negative middle-ear pressures exhibit lower PA at the low frequencies (below 2000 Hz) where stiffness makes a significant contribution to impedance (Beers et al., 2010; Kenny, 2007; Allen et al., 2005). In contrast to previous studies (Wan & Wong, 2002; Shahnaz & Davies, 2006) which have found significantly more positive TPP in their Chinese sample compared to their Caucasian sample, the sample pool of Chinese participants in the current study had significantly more negative TPP values compared to Caucasians (-7.12 compared to -10.97 daPa). The more negative TPP values in the Chinese group could result in stiffer TMs or middle ear conductive mechanisms explaining lower mean PA in the middle to low frequencies where stiffness contributes significantly to impedance (Feeney et al., 2014). However, it should be 116  noted that the contribution of negative middle ear pressure to lower PA in the low frequencies is probably negligible at best since TPP in the current study is relatively close to 0 daPa (in a normal hearing sample regardless of ethnicity or gender). However, static acoustic admittance (Ytm) may be a better indicator of the stiffness of the tympanic membrane. Consistent with previous studies, Ytm was demonstrated to be much lower in the Chinese group compared to the Caucasian group with a mean of 0.41 and 0.59 respectively in the current study (Shahnaz & Bork, 2008; Wan & Wong, 2002; Kenny, 2011; Shaw, 2009). It may follow then that the stiffness of the middle-ear transmission system in the Chinese group (indicated by lower Ytm values) may have led to higher reflectance or lower PA at the low frequencies where stiffness makes a significant contribution to impedance (Beers et al., 2010; Allen et al., 2005; Feeney et al., 2014).   4.3.2 The Effect of Gender The post-hoc tukey HSD test of the gender and frequency interaction showed that mean PA values at ambient pressure were higher between 4000 – 5000 Hz in females compared to males collapsed across all systems, ethnicities, and ears. However, the post-hoc of the gender, frequency, and system interaction showed that PA values for females were significantly higher than males in the high frequencies between 4000 – 5000 Hz for both Interacoustic devices (ReflWin and Titan). Mean PA values were also higher in females compared to males in the higher frequencies using the Mimosa devices, but this difference was not statistically significant (HearID and Otostat).  There was a tendency toward higher mean PA values in males compared to females in the low frequencies, but this trend did not reach significance. When ECV was compensated for, females demonstrated higher high-frequency PA than males at 5000 Hz across 117  all devices and anywhere between 4000 – 6300 Hz depending on the device used. The results of this study are in line with previous studies, which have found statistically significant differences in PA measurements in the high and/or low frequencies between genders across frequencies (Shahnaz et al., 2013; Rosowki et al., 2012; Feeney & Sanford., 2004; Kenny, 2011; Keefe et al., 2000; Polat et al., 2015). For instance, pooled PA data from the studies by Shahnaz and Bork (2006) and Shaw (2009) using a sample (N  = 186) of Chinese and Caucasian young adults obtained at ambient pressure with the Mimosa Acoustics system revealed that females had higher PA than males between 4000 - 5000 Hz. Feeney et al. (2014) who tested a sample of 112 adults at ambient pressure demonstrated a pattern of lower mean PA at frequencies lower than the maximum at 3000 Hz and higher mean PA values at frequencies at and greater than that maximum in female participants compared to males. Rosowski et al. (2012) who tested a sample of 29 adults (22–64 years) at ambient pressure demonstrated significantly higher mean PA at 4 kHz in female participants compared to males. Feeney and Sanford (2004) tested a sample of 40 young adults (with a mean of 21.4 years of age) and 30 older adults (with a mean of 71.6 years of age) at ambient pressure; they found that female young adults had significantly lower PA than males at 794 and 1000 Hz, but higher PA at 5040 Hz. There was a trend toward lower PA from the middle to low frequencies and higher PA at 4000 Hz in elderly females compared to males, but this didn’t reach significance. Kenny (2011) reported that Chinese females had higher PA than males at 4000 - 5000 Hz using the ReflWin. A relatively recent study by Polat et al. (2015) on a sample of Turkish young adults also found that females had significantly higher PA than males in the high frequencies from 3100 Hz to 6900 Hz using the Titan Interacoustics system at ambient pressure. In summary, when ECV was compensated for in the current study females demonstrated higher high-frequency PA than males at 5000 Hz across all devices and anywhere 118  between 4000 – 6300 Hz depending on the device used which is consistent with previous studies (Shahnaz et al., 2013; Rosowki et al., 2012; Feeney & Sanford., 2004; Kenny, 2011; Keefe et al., 2000; Polat et al., 2015)  RF and TPP did not differ significantly between genders indicating that differences in these parameters were not associated with differences in PA between genders in this study. Although BMI and ECV significantly differed between genders in this study; they did so by a small magnitude and the ANCOVA revealed that BMI and ECV didn’t account for much of the observed differences between genders. It is likely that other factors may better indicate the size of middle ear cavity, ear canal size, and could potentially explain observed differences in PA between genders. As alluded to earlier, measures of body composition including (lean mass and body fat percentage) instead of BMI may better represent differences in mass of bones and tissues between genders. This may correlate better with ossicle mass or size which have been shown to vary between ethnicities (Jayesh et al., 2014) and which can potentially account for an increase in impedance and attenuation of PA in high frequencies in males and Caucasians compared to females and Chinese subjects (Shahnaz & Bork, 2006; Relkin, 1988; Saunders et al., 1998; Allen et al., 2005). Additionally, anatomical variations in head size and distance from the lateral palpebral commissures to both the helical root and lobule have been documented between genders (Brucker, Patel, & Sullivan, 2002). These measures and others including the circumference of the head in the sagittal and frontal plane, ear canal length, ear canal diameter, and cross-sectional area of the ear canal should be investigated (Voss et al., 2013; Keefe et al., 1993). The ear canal cross-section is not uniform including local constrictions, expansions, bends, curves, and significant tapering near the tympanic membrane (Rosowski, Stenfelt, & 119  Lilly, 2013). Rosowki, Stenfelt, and Lilly (2013) have demonstrated that non-uniformities in the cross-sectional ear canal area and other complications in ear canal geometry can generate non-uniform sound pressure variations in the ear canal which propagate short distances before dying out. This complicates the measurement of PA between 4-6 kHz (Rosowki, Stenfelt, and Lilly, 2013). One might infer then that groups with larger body sizes (e.g. males and Caucasians) may have larger ear canal cross-sectional areas, differing ear canal geometries, and longer ear canal lengths at the measurement location of the probe (from osseous portion of the canal to the TM) which could explain the degradation of PA estimations between 4 – 6 kHz in these groups. Future investigations should calculate ear canal diameter and cross-sectional area of the ear canal at the measurement location using a silicone mold which has been used successfully to calculate these parameters (Keefe et al., 1993). Another helpful parameter to characterize geometric differences in ear canals between genders might also be group delay which can be calculated across frequencies. It will be discussed in depth in section 4.9.          There is some suggestion that females have a stiffer middle ear than males, much like Chinese young adults compared to Caucasians, which is reflected in the current study through significant differences in mean Ytm values (0.56 in males compared to 0.44 in females). Many studies have shown that males tend to have larger static admittance (Ytm) and narrower tympanometric width norms than females (Wiley et al., 1996; Roup et al., 1998; Shaw, 2009). Margolis, Saly, and Keefe (1999) found males had less stiffness dominated ear drums, higher middle ear resistance below 1 kHz and lower middle ear resistance between 2 and 4 kHz relative to females. They also reported that reactance values were more positive below 1500 Hz in females relative to males. Werner, Levi, and Keefe (2010) reported that reactance magnitudes at low frequencies (below 120  600 Hz) and resistance magnitudes were greater for females than males. The tendency for females to have higher stiffness dominated middle-ear transmission systems may be associated with the trend seen in the current study toward higher reflectance or lower PA at low frequencies in females compared to males where stiffness makes a larger contribution to impedance (Beers et al., 2010; Allen et al., 2005; Feeney et al., 2014).    4.3.3 The Effect of Ear  There were no differences in mean PA values and across frequencies between ears. Mean PA values (overall and across frequencies) didn’t differ between systems and ears. These results are consistent with majority of the previous literature in adults which haven’t found significant differences in PA measurements between ears (Shahnaz & Bork, 2006; Liu et al., 2008; Shaw, 2009; Burdiek & Sun, 2014; Kenny, 2011; Feeney & Sanford, 2004).  Werner et al. (2010) and Feeney (2014) did find small differences in mean PA values between ears, but note that these differences are likely smaller than the difference in PA between groups of participants with normal and impaired middle ear responses.   4.4 Test-Retest Reliability for PA Measurements at Ambient Pressure An essential requirement of a good clinical test is that it should be robust and repeatable in individuals with little variability, so that it may be clinically useful to distinguish between normal and pathological ears (Vander Werff, Prieve, and Georgantas, 2007). Statistical analysis on test-retest reliability in the current study showed that mean PA did not vary significantly between trials across frequencies for all 4 systems at either ambient or peak pressure, with the 121  exception of the Titan and ReflWin devices. Mean PA values using the Titan differed slightly between trials at 5000 Hz at ambient pressure and between 4000 – 6300 Hz at peak pressure. Mean PA values also differed in the Relfwin system at ambient pressure at 630 and 800 Hz. Subtracting the mean PA values in trial 2 from trial 1 (Appendix A.5 and A.6) revealed that mean PA values differed only by 0.02 PA units at 5000 Hz (using the Titan at ambient pressure), 0.03 PA units at 630 Hz (using the ReflWin at ambient pressure), 0.03 PA units at 800 Hz (using the ReflWin at ambient pressure), and 0.02 PA units from 4000 – 6300 Hz (using the Titan at peak pressure). This test-retest variability is much smaller than previously published studies which show variability of + 0.1 PA units between tests indicating that this test-retest difference is not greater than that which would be observed in the normal population (Feeney et al., 2014; Rosowki et al., 2012; Werner et al., 2010).    A study on test-retest reliability by Burdiek and Sun (2014) showed a statistically significant effect of consecutive wideband tympanometry tests on PA due to alteration in the viscoelastic properties of the eardrum which lead to higher compliance or lower stiffness in consecutive trials. Their study showed that PA measured at both ambient and peak pressure increased in low frequencies (below 1.5 kHz) and decreased in certain high frequencies (around 2 kHz and 5 to 6 kHz) with consecutive wideband tympanometry trials. However, the largest change generally occurred at the second trial when compared to the first trial. In the current study, the order of testing between systems and pressurization methods was varied, so it is likely that preconditioning did not play a large role in the test-retest reliability of PA measurements and this is evident in the way that mean PA values varied between trials in the Titan and ReflWin systems. For instance, the variability in PA for the Titan system at ambient and peak pressure 122  occurred such that trial 2 values were slightly higher than trial 1 values in the high frequencies at 5000 Hz at ambient pressure and 4000-6300 Hz at peak pressure. This is depicted in Figure 3.12. However, Burdiek and Sun (2014) found that PA decreased in the high frequencies with successive trials. PA was found to increase slightly in the low frequencies (630 and 800 Hz) using the ReflWin at ambient pressure; however, pre-conditioning should have affected mean PA values at peak pressure as well since it is the change in pressure that would alter the viscoelastic properties of the eardrum with consecutive trials. Consistent with Vander Werff, Prieve, and Georgantas (2007), it seems that the test-retest reliability is poorest in the low and high frequencies even when order of testing with 226 Hz tympanometry is randomized and WAI testing is conducted at ambient pressure. Much of the variability between trials in the low and high frequencies is likely due to improper sealing, shallow insertion, or orientation of the probe tip leading to inaccuracies in the measure of the stimulus level and the size of the ear canal cavity compromising the accuracy of PA estimates (Vander Werff, Prieve, & Georgantas, 2007; Allen et al., 2005; Shaw, 2009; Shaver, 2004).   Some variability in measurements between trials have been documented by many studies (Vander Werff, Prieve, & Georgantas, 2007; Beers et al., 2010; Shaw, 2009; Burdiek & Sun, 2014; Shaver, 2004; Werner et al., 2010; Feeney et al., 2014; Rosowki et al., 2012). However, the question that was addressed in the study was whether the variability in mean PA measurements poses a challenge in accurately distinguishing between normal and pathological ears.  For this purpose, a graph was generated comparing the differences in mean PA values between trials for each instrument and those between normal and pathological ears (in this case 123  in a sample of 28 individuals with surgically confirmed otosclerosis from Shahnaz et al., (2009). Refer to Figure 27 below.  Figure 27 A graph comparing differences in mean PA values between trials (using values from the descriptive statistics chart in the Appendix) across frequencies for all four systems to demonstrate differences in mean PA values between normal ears (obtained in trial 1) for each instrument and those with surgically confirmed otosclerosis.   In Figure 27 above: “A” refers to measurements made at ambient pressure, “P” refers to measurements at peak tympanometric pressure, “Ref” refers to ReflWin, “HiD” refers to HearID, and “Oto” refers to Otoslcerosis. It is evident that the differences between trials in the four devices are not as large as the differences between normal and pathological ears for all four instruments. This implies that all four instruments exhibited good test-retest reliability for diagnostic purposes.   -0.15-0.10-0.050.000.050.100.150.20100 1000 10000Ref	A	- Oto	HiDRef	P	- Oto	HiDHiD	A	- Oto	HiDOtostat	A	- Oto	HiDTitan	A	- Oto	HiDRef-A	TrialsRef-P	TrialsHearID	A	TrialsOtostat	A	TrialsTitan	A	Trials124  The test-retest reliability analysis in this study also indicated that mean PA values averaged across all frequencies varied significantly between trials in the Mimosa Acoustic devices (by approximately 0.005 using the HearID and 0.007 using the Otostat), but not the Interacoustic devices. The clinical utility of mean PA (averaged across all frequencies) has yet to be investigated to determine if it would be a clinically viable tool. The current study finds that there is very little to no variability between trials of mean PA values in all four machines. This indicates that the PA value averaged across all frequencies has good test-retest reliability.  However, averaging PA across all the testing frequencies may not be a useful tool clinically since opposing PA patterns at various frequencies might average out within groups resulting in lower observed differences between groups (e.g. ethnicities, genders, or normal and pathological groups).   4.5 The Effect of Instrument on PA Measurements at Ambient Pressure Ideally wideband reflectance systems produced by different manufacturers should produce comparable estimates of PA. However, several researchers have shown that normative data for WAI vary by the instrument used (Kenny, 2011; Shahnaz, Feeney, and Schairer, 2013; Shaw, 2007).   Resatshwane and Neely (2014) demonstrated that variability in PA values between the HearID, ReflWin, Etymotic ER-10C (ER-10C), and Hearing Assessment Reformulation Project (HARP) system existed between 500 – 6000 Hz. They attributed these differences to variation in test ear, size of ear canal and middle ear space, gender, age, ethnicity, improper placement of the probe ear tip, and movement of the ear tip during data collection. They also attributed differences to 125  distortions from the measurement equipment and errors in the determination of thevenian-equivalent parameters of the sound source (otherwise known as the source impedance and pressure) which can also result from acoustic leaks.   In line with previous research, the current study also found that mean PA values varied significantly by the system used for measurement and differed significantly between systems across frequencies. Among the Mimosa Acoustics devices, HearID and Otostat showed significant differences in mean PA measurements at 6300 Hz. Among the Interacoustics devices, Titan and ReflWin showed significant differences in mean PA measurements from 400-2000 Hz and 3150-5000 Hz.  Mean PA values differed significantly between ReflWin and Otostat at 250 Hz and 800-2000 Hz. They also differed significantly between ReflWin and HearID at 250, 630-1000, 2000, and 6300 Hz. They differed between Titan and HearID at 250-1600 Hz and 4000 – 6300 Hz. They differed significantly between Titan and Otostat measurements at 250-630, 1000-1600, and 4000-5000 Hz.   Some reasons that PA values might vary slightly based on the instrument used include differences in calibration methods used for these devices. Both the Mimosa Acoustics systems use a four-chamber calibration technique in comparison to the two-tube system of the ReflWin and Titan Interacoustics devices. Keefe et al. (1992) have demonstrated that two tubes are sufficient to determine all Thevenin parameters used in the calculation of energy reflectance, but they admit that the use of more than two tubes could result in more robust estimates of PA values. Alternatively, differences could arise due to the manner in which ear canal area is estimated by the four systems. When the ear canal is of a different diameter than the calibration 126  tubes, the effective Thevenin equivalents change leading to errors in the calculation of PA (Sanford & Feeney, 2004). The Reflwin system uses an average estimate of the human ear canal diameter in all calculations of energy reflectance, where the Mimosa Acoustics HearID system determines ear canal area by using an ear canal diameter associated with the size of probe tip used in the measurement (Shaw, 2009; Mimosa Acoustics, 2012). This may mean that estimates of PA from the Mimosa Acoustics systems may be more accurate representations of PA than those made by the Interacoustics systems especially in the low frequencies (Sanford & Feeney, 2008; Feeney & Sanford, 2004; Keefe et al., 1993).In addition, the Interacoustics devices used a stimulus level of 100 dB SPL while the Mimosa Acoustics devices used a stimulus level of 60 dB SPL which may have differentially impacted the accuracy of PA estimates in the low frequencies (Vander Werff, Prieve, & Georgantas, 2007). Another reason for the observed differences between instruments is that the probe tip size is selected by the clinician to fit each subject’s ear optimally and then indicated in the user interface of the computer system. This might lead to variable estimations of the ear canal area by the Mimosa Acoustics systems which would in turn result in differing estimates of PA. Distortions from the measurement equipment (such as placement of the probe wires) were observed to create some variability in the low frequencies especially when using the HearID system (Resatshwane and Neely, 2014).   A study by Resatshwane and Neely (2015) demonstrated how reflectance measurements in acoustic horns could be utilized to create reflectance standards that could serve as a means for validating measurements and checking the consistency across measurement equipment with extended bandwidth (up to 20 kHz). Their study compared theoretical WAI parameters (derived from published equations by earlier researchers) with measured values using the Etymotic 127  Research 10-C system (ER-10C) and Hearing Assessment Reformulation Project (HARP) system in acoustic horns with exponential, conical, and parabolic shapes. Issues such as air leaks, errors in thevenin calibration, movement of the probe and eartip within the canal during measurements and other intermittent equipment issues could be identified this way. The researchers found that pearson correlations between theoretical and measured reflectance parameters were > 0.95 suggesting that the validation procedure was effective. The authors did not use this procedure to validate measurements utilizing devices from the current study. However, future investigations should incorporate validation procedures like these to determine the extent of variability in PA estimates due to the equipment itself.     Mean PA values in 1/3rd octave frequency intervals have been compared for the devices used in the study with previous literature using a similar version of the device below.    128   Figure 28 A depiction of the average PA values and standard deviations across frequency using the ReflWin Interactoustics in the current study at ambient pressure as compared to earlier versions of the device documented in the literature.  The current study yielded lower estimates of PA at the low frequencies compared to most studies indicating a lower probability that variation in PA values are due to factors related to test-retest reliability such as depth of insertion of the probe (Vanderwarff, Prieve, & Georgantas, 2007). The variation in PA across studies may reflect differences in software versions utilized across studies. Earlier versions of the software utilized by Feeney et al. (2004) had ER10-C foam probe configurations which didn’t reduce the effect of non-uniform sound waves created by the receiver-load interface, thus decreasing accuracy of impedance measurements. Sanford and Feeney (2008) made measurements using Welch Allyn prototype diagnostic middle ear analyzer system with a probe which consisted of a custom made receiver/microphone assembly. They also used broadband acoustic chirps instead of clicks as was done in the current study. Shaw (2009) 0.000.100.200.300.400.500.600.700.800.901.00200 2000Current	StudyShaw	(2009)Sanford	&	Feeney(2008)Feeney	et	al.	(2004)129  used an older version of the ReflWin Interacoustics system (Eclipse – v.1) compared	to	the	current	study	(Software Release Version V.3.2.1). In summary, factors related to the type of probe, stimulus, and potential differences in calibration could have led to variations in the calculation of impedance and PA using the ReflWin system between studies.     Figure 29 A depiction of the average PA values and standard deviations across frequency using the Mimosa Acousics devices (HearID and Otostat) in the current study as compared to earlier versions of the PC-based Mimosa devices documented in the literature.  For measurements made using the Mimosa Acoustics systems (Otostat and HearID), it seems that the current study is in agreement with most studies especially in the low and high frequencies. In fact, estimates of PA in the low frequencies in the current study are slightly lower than other studies indicating lower probability of errors in WAI measurements due to factors related to test-retest reliability. Several studies have reported greater variability in measurements between instruments for middle to high frequencies compared to low frequencies (e.g., Werner et al., 2010; Voss et al., 2012). Due to the fact that mid-frequency regions are reputed to produce 0.000.100.200.300.400.500.600.700.800.901.00200 2000Current	Study	(HearID	Mimosa)Shahnaz	&	Bork	(2006)Shaw	(2009)Voss	et	al.	(1996)Current	Study	(Otostat	Mimosa)130  reliable estimates of PA (Vanderwarff, Prieve, & Georgantas, 2007), this variability may in fact reflect stem from differences in sample size, age, test ear, ear canal size, middle ear cavity volume, ethnicity, and instrument used across studies.    Figure 30 A depiction of the average PA values and standard deviations across frequency using the Titan Interacoustics device in the current study as compared to the Titan Interacoustics device used in a fairly recent study by Polat et al. (2015) at ambient pressure.   For measurements made using the Titan system, it seems PA values are similar between the current study and that by in the current study and that by Polat et al. (2015) especially in the high and low frequencies. This indicates that the slight differences between studies likely don’t reflect measurement error related to depth of insertion of the probe or acoustic leaks which tend to exert their effects in the low and high frequencies (Vanderwarff, Prieve, & Georgantas, 2007). Higher PA values by Polat et al. (2015) in the mid-frequency range likely reflect variation in age, resonance frequency, and ear canal volume between studies. More specifically, Polat et al., 0.000.100.200.300.400.500.600.700.800.901.00200 2000Current	StudyPolat	et	al.	(2015)131  (2015) performed WAI tests on a slightly less variable age range (ranging from18.3 – 26.2 years compared to 18 - 34 years in the current study), obtained lower estimates of mean ear canal volume (from a mean of 1.16 - 0.93 in their study compared to a mean of 1.31 - 1.01 for the current study), and lower estimates of resonance frequencies (from a mean of 992 – 993 Hz in their study compared to a mean of  974.59 – 1340.59 Hz in our study). They also used a different version of the Titan software compared to our study (Titan version 3.1 in their study compared to Titan version V.1.2.1). These factors together could have accounted for differences in PA values between these studies at the middle frequencies.    The current study found that the differences between trials for normal hearing individuals in all four instruments were not as pronounced as those between normal hearing individuals and those with a middle ear pathology such as otosclerosis (as seen from Figure 5.1). This theoretically indicates that norms obtained from any of the four instruments may be used to distinguish between normal and pathological ears in a given instrument. However, instrument specific norms may still be used to improve the sensitivity and specificity of WAI testing in distinguishing middle ear pathology in some cases.   A receiver operating characteristic (ROC) curve was generated using PA data obtained from normal hearing participants at 800 and 2000 Hz from all four instruments and those obtained from individuals with surgically confirmed  otosclerosis (Shahnaz et al, 2009) using the HearID system. These frequencies were selected for analysis, because they are points at which the greatest differences in mean PA values occur between normal and pathological ears (See Figure 5.1). These frequencies are also within the range of frequencies found to differ significantly in 132  PA between normal and otoslcerotic ears (Shahnaz et al., 2009; Shahnaz, Longrdige, & Bell, 2009). The ROC curves were measured at these frequencies to statistically compare the diagnostic performance of PA measurements at 800 Hz and 2000 Hz as a function of norms utilized from 4 different systems at either ambient or peak tympanometric pressure.   An ROC curve is a graph that plots the true positive rate as a function of the false positive rate at different cut-off points (mean PA values in this case). The area under the ROC (AUROC) and 95% CI which is the interval in which the true (population) AUROC curve lies with 95% confidence (Hilgers, 1991) wasalso generated AUROC plots using data from all four instruments at 800 Hz and 2000 Hz as compared to data from surgically confirmed otosclerotic ears using the HearID system at 800 and 2000 Hz are represented in Figure 31 and 32 respectively. A summary of AUROC plots at 800 Hz and 2000 Hz and corresponding 95% confidence intervals along with pair-wise comparison of AUROCs between systems can be found in Table 9 and 10 below. Detailed results of the ROC analysis can be found in Table B. 19 and B.20 of the appendix. 133   Figure 31 Receiver operating characteristic curve analysis for power absorbance values at 800 Hz using the HearID at ambient pressure, Otostat at ambient pressure, ReflWin at ambient and peak pressure, and Titan at ambient and peak pressure.  134   Figure 32 Receiver operating characteristic curve analysis for power absorbance values at 2000 Hz using the HearID at ambient pressure, Otostat at ambient pressure, ReflWin at ambient and peak pressure, and Titan at ambient and peak pressure.          135  AUROC Plots and 95% Cis AUROC SD 95% CI HiD_800_Hz 0.689 0.0695 0.593 to 0.774 Ot_800_Hz 0.697 0.0687 0.602 to 0.782 Ref_Ambient_Pressure_800_Hz 0.632 0.0667 0.534 to 0.722 Ref_Peak_Pressure_800_Hz 0.822 0.0544 0.737 to 0.888 Titan_Ambient_Pressure_800_Hz 0.755 0.0623 0.663 to 0.832 Titan_Peak_Pressure_800_Hz 0.789 0.0581 0.700 to 0.861  Pairwise Comparison between AUROCs Difference Between AUROCs SE 95% CI Z  P HiD_800_Hz ~ Ot_800_Hz 0.00838 0.0189 -0.0287 to 0.0454 0.443 0.6577 HiD_800_Hz ~ Ref_Ambient_800_Hz 0.0571 0.0261 0.00588 to 0.108 2.185 0.0289 HiD_800_Hz ~ Ref_Peak_800_Hz 0.133 0.0333 0.0674 to 0.198 3.984 0.0001 HiD_800_Hz ~ Titan_Ambient_800_Hz 0.0659 0.0283 0.0104 to 0.121 2.327 0.0200 HiD_800_Hz ~ Titan_Peak_800_Hz 0.0996 0.0327 0.0355 to 0.164 3.043 0.0023 Ot_800_Hz ~ Ref_Ambient_800_Hz 0.0655 0.0303 0.00600 to 0.125 2.158 0.0309 Ot_800_Hz ~ Ref_Peak_800_Hz 0.124 0.0317 0.0622 to 0.186 3.925 0.0001 Ot_800_Hz ~ Titan_Ambient_800_Hz 0.0575 0.0254 0.00782 to 0.107 2.268 0.0233 Ot_800_Hz ~ Titan_Peak_800_Hz 0.0913 0.0295 0.0334 to 0.149 3.094 0.0020 Ref_Ambient_800_Hz ~  Ref_Peak_800_Hz 0.190 0.0345 0.122 to 0.257 5.497  < 0.0001 Ref_Ambient_800_Hz ~  Titan_Ambient_800_Hz 0.123 0.0342 0.0560 to 0.190 3.595 0.0003 Ref_Ambient_800_Hz ~  Titan_Peak_800_Hz 0.157 0.0356 0.0870 to 0.227 4.404 < 0.0001 Ref_Peak_800_Hz ~  Titan_Ambient_800_Hz 0.0668 0.0259 0.0160 to 0.118 2.576 0.0100 Ref_Peak_800_Hz ~  Titan_Peak_800_Hz 0.0331 0.0226 -0.0113 to 0.0774 1.462 0.1438 Titan_Ambient_800_Hz ~ Titan_Peak_800_Hz 0.0337 0.0103 0.0135 to 0.0540 3.264 0.0011 Table 9 Summary of AUROC plots and 95% CI along with pair-wise comparison of AUROC plots for PA at 800 Hz between HearId (HiD) at ambient pressure, Otostat (Ot) at ambient pressure, ReflWin (Ref) at ambient pressure, Titan at ambient pressure, ReflWin at peak pressure, and Titan at peak pressure. All highlighted cells represent pairwise comparisons which were significant (p < 0.05).         136  AUROC Plots and 95% CIs AUC SE a 95% CI b HiD_2000_Hz 0.629 0.0651 0.531 to 0.720 Ot_2000_Hz 0.627 0.0647 0.529 to 0.717 Ref_Ambient_Pressure_2000_Hz 0.673 0.0585 0.576 to 0.760 Ref_Peak_Pressure_2000_Hz 0.622 0.0664 0.524 to 0.713 Titan_Ambient_Pressure_2000_Hz 0.620 0.0678 0.522 to 0.712 Titan_Peak_Pressure_2000_Hz 0.644 0.0667 0.547 to 0.734  Pairwise Comparison between AUROCs Difference Between AUROCs SE 95% CI Z  P HiD_2000_Hz ~ Ot_2000_Hz 0.00265 0.0274 -0.0510 to 0.0563 0.0967 0.9230 HiD_2000_Hz ~ Ref_Ambient_2000_Hz 0.0437 0.0370 -0.0289 to 0.116 1.179 0.2384 HiD_2000_Hz ~ Ref_Peak_2000_Hz 0.00705 0.0374 -0.0662 to 0.0803 0.189 0.8502 HiD_2000_Hz ~ Titan_Ambient_2000_Hz 0.00882 0.0358 -0.0614 to 0.0790 0.246 0.8055 HiD_2000_Hz ~ Titan_Peak_2000_Hz 0.0150 0.0361 -0.0558 to 0.0857 0.415 0.6779 Ot_2000_Hz ~ Ref_Ambient_2000_Hz 0.0463 0.0423 -0.0367 to 0.129 1.094 0.2740 Ot_2000_Hz ~ Ref_Peak_2000_Hz 0.00441 0.0403 -0.0745 to 0.0833 0.110 0.9128 Ot_2000_Hz ~ Titan_Ambient_2000_Hz 0.00617 0.0347 -0.0619 to 0.0742 0.178 0.8589 Ot_2000_Hz ~ Titan_Peak_2000_Hz 0.0176 0.0352 -0.0515 to 0.0867 0.500 0.6168 Ref_Ambient_2000_Hz ~  Ref_Peak_2000_Hz 0.0507 0.0395 -0.0268 to 0.128 1.282 0.1998 Ref_Ambient_2000_Hz ~  Titan_Ambient_2000_Hz 0.0525 0.0434 -0.0325 to 0.137 1.210 0.2264 Ref_Ambient_2000_Hz ~  Titan_Peak_2000_Hz 0.0287 0.0427 -0.0550 to 0.112 0.672 0.5018 Ref_Peak_2000_Hz ~  Titan_Ambient_2000_Hz 0.00176 0.0411 -0.0787 to 0.0823 0.0429 0.9657 Ref_Peak_2000_Hz ~  Titan_Peak_2000_Hz 0.0220 0.0410 -0.0582 to 0.102 0.538 0.5904 Titan_Ambient_2000_Hz ~ Titan_Peak_2000_Hz 0.0238 0.00647 0.0111 to 0.0365 3.678 0.0002 Table 10 Summary of AUROC plots and 95% CI along with pair-wise comparison of AUROC plots for PA at 2000 Hz between HearId (HiD), Otostat (Ot), ReflWin (Ref), and Titan at ambient pressure along with ReflWin and Titan at peak pressure. All highlighted cells represent pairwise comparisons which reached significance.  The AUROCs for all parameters with their corresponding 95% confidence intervals were above a level attributable to chance (Table 4.1 and 4.2), indicating that they were able to distinguish 137  between otosclerotic and normal ears. In other words, using a PA value from any system at 800 Hz and 2000 Hz to diagnose otosclerosis was better than chance.  Pairwise comparisons of AUROC curves were also done at both frequencies to compare the performance of normative data sets from the 4 different systems in distinguishing Otosclerotic ears. This test compared the statistical significance of the differences between AUROC curves from data obtained by 2 systems (Hanley & McNeil, 1983).   The pair-wise comparisons at 800 Hz revealed that using instrument specific norms (e.g. HearID norms to distinguish otoslcerotic ears obtained from the HearID device) did not improve the ability to detect otosclerotic ears in in most cases with one exception. Norms from the HearID system were better able to correctly identify otosclerotic ears compared to norms from the Titan system at peak pressure.   At 2000 Hz, there were no statistically significant differences in observed and calculated differences between AUROC curves obtained in the pair-wise comparison between normative data from any device and HearID. In other words, HearID norms did not improve test performance in identifying otosclerotic ears obtained from the HearID system when compared to other instrument specific norms.  Hence, instrument specific norms did not improve test performance at 2000 Hz. The current study has only compared instrument specific data at two frequencies to identify otosclerotic ears. More reliable conclusions can be made about whether instrument specific norms are warranted when a larger frequency bin is analyzed in this manner. 138  After all, the reason that wideband reflectance is being investigated is that it provides information about middle ear status at a wider range of frequencies compared to tympanometry.   From the ROC analysis in this study, it can be concluded that instrument specific norms do not improve the ability to distinguish between normal and pathological ears at 800 and 2000 Hz for the most part. These results are similar to Shaw (2009) who also did not find an improvement in test sensitivity or specificity as a result of using instrument specific norms (e.g. HearID norms) for identifying otosclerotic ears obtained by Shahnaz et al. (2009). However, sweeping generalizations about whether instrument specific norms are useful in identifying otosclerotic ears cannot be made at this time. Further investigation requiring a larger sample size, pathological ears tested using all devices under study, wider frequency bins for analysis, and ears with various types of middle ear pathologies are needed for definite conclusions to be drawn. What can be concluded is that normative data from all four instruments do perform much better than chance (with AUROCs ranging from 0.620 to 0.822) in identifying otosclerotic ears from the HearID system at 800 Hz and 2000 Hz.      	 4.6 The Effect of Ethnicity, Instrument, Gender, and Ear on Ambient vs. Peak Pressure Measurements Overall, mean PA values at peak pressure were significantly higher than at ambient pressure collapsed across systems, genders, ethnicities, and ears. Mean PA values at both ambient and peak pressure individually (collapsed across systems, genders, ears, and ethnicities) displayed a similar pattern such that PA tended to decrease below 3150 Hz (the maximum) and decrease 139  again up to 8000 Hz. This pattern is consistent with previous literature which shows that PA tends to decrease below a maximum (approximately between 1 and 4 kHz) prior to decreasing up to 8 kHz at ambient and peak pressure in adults (Feeney & Sanford, 2004; Keefe et al., 1993; Kenny, 2011; Margolis, Saly, & Keefe, 1999; Shaw, 2009; Shaver, 2004; Sanford & Feeney, 2008; Shahnaz & Bork, 2006; Werner et al., 2010). The PA maximum is in the range of frequencies most important for speech perception and energy transmission into the middle ear is most efficient at this range (Keefe et al., 1993).   4.6.1 Gender  It is interesting to note that WAI testing at peak tympanometric pressure allowed more significant differentiation of PA values between genders at a broader range of frequencies than testing at ambient pressure alone. More specifically, males had significantly higher mean PA values (compared to females) between 500 – 800 Hz and 8000 Hz and significantly lower mean PA values between 4000 – 5000 Hz when measurements were made at peak pressure. However, males exhibited a pattern of higher mean PA values (compared to females) at low frequencies and significantly lower mean PA values at 4000 – 5000 Hz when measurements were made at ambient pressure. There was only a trend toward males demonstrating higher PA values at low frequencies at ambient pressure, but this trend became more significant when measurements were made at peak pressure (between 500 – 800 Hz). In summary, females demonstrated significantly higher high-frequency PA, but only a trend toward lower low-frequency PA at ambient pressure; however, they demonstrated significantly higher high-frequency PA and significantly lower low-frequency PA at tympanometric peak pressure. This may be due to the fact that ambient WAI measurements assume maximum compliance occurs at 0 daPa, while 140  pressurized WAI measurements occur at peak tympanometric pressure. The average TPP for the current study was slightly more negative than 0 daPa in both genders and ethnicities. Pressurized measurements occurring at TPP allowed the assessment of middle ear status at the pressure at which the middle ear exhibits the greatest tympanic membrane mobility or absorbs sound energy maximally (Onusko, 2014). Hence, PA measurements at peak tympanometric pressure may have allowed maximal absorption of the sound stimuli from the probe in order to more accurately reflect the status of the middle ear between genders.   Although previous studies have investigated the differences in PA measurements between ambient pressure and TPP conditions, they have not commented on how pressurizing the ear affected observed differences in PA between groups such as gender across frequencies (Liu et al., 2008; Burdiek & Sun, 2014; Shaw, 2009; Kenny, 2011). However, some studies have found differences between genders in the low and high frequencies at ambient pressure.  For instance, Feeney and Sanford (2004) found that the males, in their sample of young adults, had significantly higher PA at 794 and 1000 Hz (low frequency) and lower at 5040 Hz (high frequency) than females when measurements were made at ambient pressure. Werner et al. (2010) found that reactance was lower in the low frequencies in males compared to females which would be consistent with higher PA values in this low frequency range for males. The authors attributed the lower middle ear impedance in males (in comparison to females) to differences in ear canal area and body size which relate to larger external and middle ear anatomies in males. Many studies have demonstrated observed differences in PA between genders in the high frequencies, but not necessarily the low frequencies. Perhaps, this may be due to the fact that the TPP in those studies and the current study varied significantly enough 141  from ambient pressure to require pressurization in order to accurately reflect middle ear absorption in the low frequencies for both genders (Allen et al., 2005).   Future studies should focus on whether the differences between genders are larger than those between normal ear and ears of various middle ear pathologies. Furthermore, whether using gender specific norms would increase the sensitivity and specificity of the assessment of various middle ear conditions.   4.6.2 Ethnicity Consistent with previous studies, the Caucasian group had higher mean PA values compared to the Chinese group at both peak and ambient pressure (Shaw, 2009). At peak pressure, Caucasians had significantly higher mean PA values between 400 – 1250 Hz and significantly lower values between 4000 – 8000 Hz compared to the Chinese. At ambient pressure, Caucasians had significantly higher mean PA values between 500 – 1250 Hz and lower mean PA values between 4000 – 8000 Hz. Again, it is interesting to note that WAI measurements performed at TPP allowed more accurately reflect differences between ethnicities at a slightly wider range of frequencies compared to those performed at 0 daPa. This is because measurements made at TPP occur at the pressure at which maximal compliance occurs which was slightly more negative than 0 daPa in the current study. The clinical implications are that WAI measurements made at TPP may more accurately reflect middle ear status and be more valuable in reflecting differences between normal and pathological groups.   142  The pattern of higher PA in the low frequencies and lower PA in the high frequencies in Caucasians compared to the Chinese is consistent with previous studies (Shahnaz & Bork, 2006; Kenny, 2011; Shaw, 2009). Kenny (2011) found that Caucasians produced significantly higher absorbance from 800 – 1250 Hz while Chinese participants produced significantly higher absorbance between 5000 Hz and 8000 Hz. Shahnaz and Bork (2006) found that the Caucasian group had higher PA values than the Chinese group between 460 and 1500 Hz and lower PA values between 3891 and 6000 Hz. In addition, Shaw (2009) similarly found that PA values for Caucasian young adults were higher at or below 1250 Hz, similar between 1600 and 3150 Hz and lower between 4000 to 6000 Hz. The current study is in agreement with previous studies on ethnicity in normative data collection for WAI. Future studies should focus on whether the differences between ethnicities are larger than those between normal ears and ears of various pathologies. Furthermore, whether using ethnicity specific norms would increase the sensitivity and specificity of the assessment of various middle ear conditions.  4.6.3 Ear Mean PA measurements did not vary significantly by ear overall or across frequencies collapsed across systems, pressurization methods, genders, and ethnicities. Mean PA values didn’t differ significantly between the left and right ear between trials. Mean PA values did not differ significantly between ears during trial 1 or trial 2 when obtained at either peak or ambient pressure. This is similar to work in previous studies on normative data collection in WAI in young adults (Feeney & Sanford, 2004; Werner et al., 2010; Feeney et al., 2014; Polat et al., 2015).  143  4.6.4 System Mean PA did vary significantly between systems when testing a specific ethnicity (Chinese or Caucasian) at a certain pressurization method (ambient or peak pressure). Mean PA varied significantly between pressurization methods within any given ethnicity in ReflWin system, but not in the Titan system.    PA measurements made using ReflWin were significantly higher at peak pressure than ambient pressure between 250-2000 Hz and lower between 4000-5000 Hz (collapsed across trials and during each trial individually). PA measurements made using the Titan collapsed across trials and trial 1were significantly higher in the low frequencies only (from 400 – 1000 Hz) at peak pressure compared to ambient pressure. However, PA measurements using the Titan were significantly higher in the low frequencies (between 315 – 1000) and lower in the middle frequencies (3150 – 4000 Hz) when measured at peak pressure compared to ambient pressure during Trial 2. This may be evidence for preconditioning effect at least in the Titan. Repeatedly changing the pressure within the ear canal (as was done in the current study) decreases the stiffness of the tympanic membrane thereby altering its viscoelastic properties and increasing the acoustic admittance or absorption of energy at low frequencies (Gaihede, 1996; Burdiek & Sun, 2014). Repeated pressure loading of the middle ear system can also enlarge the difference between mass reactance and stiffness reactance of the middle ear thereby increasing total reactance, impedance, and decreasing PA at high frequencies (Burdiek & Sun, 2014). Although care was taken in the current study to vary the order of ambient and peak pressure testing for all subjects, no research has reported on the time course of the tympanometric preconditioning effect. All that is known currently is that a complete recovery of the eardrum compliance in low 144  frequency tympanometry has been observed 24 hours after successive tympanometry trials (Gaihede, 1996; Osguthorpe & Lam, 1981). It is possible that although the order of testing was varied, preconditioning may have played some role in PA estimates at peak pressure as each participant underwent pressurized WAI testing at least ten times (four times for WAI at peak pressure using the Interacoustics systems, twice for 226 Hz tympanometry using the Titan, twice for 678 Hz tympanometry, and twice for 1000 Hz tympanometry using the Titan) in the span of forty-five minutes to an hour. At times the probe was reinserted and the ear was re-tested in order to ensure PA measurements below 250 Hz were < 0.2 to provide valid results as has been demonstrated in other studies (Feeney and Sanford, 2004; Rosowski et al., 2012 ).  Future investigations should perform pressurized WAI testing at set time intervals to determine the length of time required for the effects of preconditioning to dissipate from one test to the next. None the less, a pattern of higher PA in the low frequencies and lower PA in the high frequencies at peak pressure compared to ambient pressure has been demonstrated in many studies (Burdiek & Sun, 2014; Liu et al., 2008; Shaver, 2004; Kenny, 2011). The change in PA between ambient and peak pressure conditions has been attributed to the stiffening of the middle ear and ear drum which occurs with pressurization (Margolis, Saley, & Keefe, 1999; Gaihede, 1996).  Margolis, Saly, and Keefe (1999) found PA at peak pressure tends to be higher in the low frequencies and lower in the higher frequencies just above resonant frequency (approximately 1121 Hz) when using a system similar to the one described by Keefe et al. (1993). Shaver (2004) demonstrated that PA measurements using the ReflWin at peak pressure were significantly higher than ambient pressure from 1500 to 3000 Hz.  Kenny (2011) found PA values were higher 145  in both ethnicities at low frequencies (250- 2500 Hz in Caucasians and 500 – 2500 Hz in Chinese) and lower in Caucasian participants at the high frequencies from 4000 – 5000 Hz when measuring at peak pressure compared to ambient pressure using the ReflWin system. Liu et al. (2008) had expected that PA values would be similar when measured at either tympanometric peak pressure (TPP) or static pressure using an older version of the ReflWin system, given that their sample’s mean TPP was within one standard deviation of ambient pressure (much like the current study). However, similar to the current study Liu et al. (2008) found that PA values at TPP were higher than at ambient pressure in the low frequencies and slightly lower at high frequencies with the largest changes at 840 Hz and 4760 Hz, in the low and high frequencies respectively. They attributed the difference between measurements to positive residual pressure during probe tip insertion right before the ambient pressure measurements leading to a smaller measurement of ear canal volume and increase in air pressure. They added that the residual air pressure could have been controlled for by providing ventilation in the probe or setting the pressure back to zero using the pressure pump before ambient pressure measurements.   As seen in Figure 3.10, mean PA values obtained at peak pressure differed significantly between the Titan and ReflWin from 630-1000, 3150, 4000, and 8000 Hz. However, mean PA values obtained at ambient pressure differed significantly between the Titan and ReflWin systems from 250-2000 Hz and 3150-8000 Hz. The greatest difference in mean PA values between systems occurred at ambient pressure implying that the two systems may be making PA measurements at ambient pressure conditions quite differently compared to peak pressure. Perhaps as Liu et al. (2008) had suggested, the residual air pressure needed to be controlled for in the ReflWin by providing ventilation in the probe or setting the pressure back to zero using the pressure pump 146  before ambient pressure measurements. According to an email correspondence with Interacoustics, the newer device (Titan) has adjusted for residual air pressure by setting the pressure pump to 0 daPa when ambient pressure measurements are made. Some researchers have found that removing the air tube from the back of the AT235 tympanometer (in the ReflWin system) during ambient testing gives a more accurate measurement at ambient pressure. This may have produced more congruent readings between the Titan and Reflwin systems at ambient pressure for research purposes. However, it would likely not need to be done clinically to identify ears with middle ear pathology since both the normal and diseased populations would be assessed under the same condition (with the air tube attached to the back of the AT235 tympanometer).        4.7 The Effect of Gender, Instrument, and Ethnicity on Frequency-Averaged PA Using Wideband Tympanometry The current study used the Titan Interacoustics hand-held device to calculate frequency-averaged power absorbance between 375 – 2000 Hz swept across pressure (daPa) during WAI measurements. The reason that PA was averaged between only 375 – 2000 Hz across pressure is because the Titan software does not allow the user to adjust the frequency bandwidth. However, this bandwidth has its advantages : (1) setting a bandwidth of 0.38 – 2 kHz in the calculation of PA under tympanometric conditions has been shown to generate only single-peaked PA tympanograms which are easy to interpret, relatively free of the effects of physiological noise, and highly sensitive to changes in pressure (Liu et al., 2008); (2) WAI in the 2000 – 4000 Hz range has been demonstrated to be a sensitive predictor of conductive hearing loss compared to 147  traditional tympanometry (Pikorski et al., 1999; Keefe et al., 1993; Keefe & Simmons, 2003); (3) PA measurements are less susceptible to error in the middle frequencies due to factors related to test-retest reliability including measurement location of the probe (Vander Werff, Prieve, and Georgantas, 2007; Werner et al., 2010; Feeney et al., 2014; Rosowki et al., 2012).    Given the advancements that have recently emerged in more accurately characterizing middle-ear status with wideband tympanometry, the goal of the current study was to create a repository of normative data categorized by gender and ethnicity using the Titan Interacoustics hand-held device. The current study found that mean frequency-averaged PA (between 375 – 2000 Hz) varied by pressure level. Positive and negative pressure levels relative to the TPP led to decreases in frequency-averaged PA in a pattern identical to traditional 226 Hz tympanometry. As was illustrated in Figure 3.15 and 3.16, the current study exhibits a single peaked wideband admittance tympanogram similar to that obtained by Liu et al. (2008) in a sample of 48 adult  subjects (with a mean age of 33.8 + 10 years) which utilized an older system that calculated frequency-averaged PA (between 380 – 2000 Hz) using a sweep pressure paradigm. It was also similar to single-peaked transmittance tympanograms obtained at various static pressures averaged between 2.5 – 3 kHz by Keefe and Simmons (2003) for a sample of 42 ears from young adults aged 19.2 + 10.3 years. The WT patterns obtained in the current study were similar to the single-peaked wideband admittance magnitude tympanograms (in mmho) obtained in a group of 20 young adults with a mean age of 24.6 + 2.9 years by Sanford & Feeney, 2008. It is interesting to note that Sanford and Feeney (2008) found that the young adults in their sample (N = 20) exhibited single peaked wideband admittance tympanograms (when plotting admittance magnitude as a function of air pressure) from 0.25 to 1 kHz, followed by a 2 kHz tympanogram 148  with a notch (which is defined as an abrupt decrease in admittance magnitude followed by an increase as a function of pressure) returning to single peaked functions at 4 kHz. The results of Sanford and Feeney (2008) imply that the tympanometric bandwidth used to assess middle ear status in WT may potentially be expanded to include 4 kHz in future studies in order to assess middle ear status at a wider range of frequencies important for speech and understanding without sacrificing single peaked tympanometric functions for ease of interpretation.   In traditional 226 Hz tympanometry, the peak of the tympanogram (or maximal static acoustic admittance) occurs at peak tympanometric pressure (TPP) as the middle ear exhibits the greatest absorption of sound energy at this point (Onusko, 2014). TPP usually occurs around atmospheric pressure (0 daPa) in a normal hearing sample as the eustachian tube functions normally to equalize pressure in the middle ear with that of the atmosphere. As seen in the current study, WT follows a similar pattern indicating maximal frequency-averaged PA at TPP. However, it also provides more information than 226 Hz tympanometry by calculating average PA between 375 – 2000 Hz (which represents impedance of the annular ligament and middle ear cavity in addition to the tympanic membrane) at every pressure level while traditional tympanometry obtains admittance at only 226 Hz at every pressure level. Since measures of PA in the middle frequencies have been shown to be a more sensitive measure of conductive hearing loss compared to traditional tympanometry (Pikorski et al., 1999), it is advantageous to assess the middle ear at a wider frequency range under tympanometric conditions especially since the output are still single peaked tympanograms which are easy to interpret clinically. It may be argued that using frequency-averaged PA in a small mid-frequency band discards information obtained from higher frequencies which may be more sensitive to certain middle ear pathologies. 149  Therefore, future versions of the Titan system should allow the researcher or clinician to set the frequency bandwidth desired in order to improve test performance in testing a particular pathology. However, it should be noted that changing this bandwidth may alter the shape of the tympanogram making it a little less practical clinically.   The current study is one of the first to determine the effect of ethnicity and gender on WT. It found that males had higher mean frequency-averaged PA compared to females (0.23 and 0.17 respectively). Caucasians had higher mean frequency-averaged PA values compared to the Chinese (0.22 and 0.18 respectively). Mean frequency-averaged PA values for males were significantly higher than females between +4 and -74 daPa. In addition, mean frequency-averaged PA values for Caucasians were significantly higher than the Chinese between +66 and -70 daPa. This difference was expected given that males had higher mean PA values compared to females between 500 – 800 Hz and Caucasians had higher values than the Chinese between 400 – 1250 Hz at peak tympanometric pressure. Frequency averaged PA (between 380 – 2000 Hz) values were derived from pressurized WAI measurements in this study. These results are consistent with previous studies which have documented differences due to gender and ethnicity on normative data on WAI (at ambient and peak pressure) and 226 Hz tympanometry (Beers et al., 2010; Shahnaz & Davies, 2003; Shahnaz & Bork, 2006; Shahnaz et al., 2013; Shaw, 2009; Wan & Wong, 2002). As elaborated on earlier in the discussion, the smaller middle ear cavities and ear canal sizes (associated with Chinese and female groups) are thought to be less compliant or more stiffness based middle ear transmission systems resulting in lower static acoustic admittance values at 226 Hz and lower PA in the low-mid frequencies (Wan & Wong, 2002; 150  Kenny, 2011; Shahnaz & Davies, 2006; Shahnaz & Bork, 2006) at which frequency averaged PA values are derived.   It is interesting to note that the differences observed between genders and ethnicities using frequency-averaged PA (between 375 – 2000 Hz) were more pronounced than differences between these groups using mean PA (averaged between 226 – 8000 Hz) at both TPP and ambient pressure. For instance, the difference in mean PA (obtained from 226 – 8000 Hz using one-third octave analysis) between genders using data from the Titan and ReflWin was approximately 0.02 PA units (0.44 in males and 0.42 in females) at ambient pressure and 0.03 PA units (mean PA values of 0.47 in males compared to 0.44 in females) at peak pressure. However, the difference in frequency-averaged PA between genders using WT was much more pronounced at approximately 0.06 PA units (mean PA was 0.23 in males and 0.17 in females). Similarly, mean PA between ethnicities differed by 0.03 PA units at peak pressure (0.466 in the Caucasians and 0.444 in Chinese) and 0.02 PA units at ambient pressure (0.436 in the Caucasians and 0.423 in Chinese) while mean frequency-averaged PA in WT differed by 0.04 PA units (0.22 and 0.18 respectively).  Pressurizing the middle-ear tends to load or stress the eardrum (Gaiehede, 1996) which may have potentially led to accentuated differences in PA between groups at peak pressure. In addition, since frequency-averaged PA was assessed in a smaller frequency range (specifically between 375 – 2000 Hz) compared to PA overall, accentuated differences between groups make sense since both genders and ethnicities displayed significant differences in pressurized WAI testing at low frequencies. However, PA overall averaged out the opposing high and low frequency PA patterns seen in both genders and ethnicities.  Future investigations should determine if the difference between normal and 151  pathological middle ear groups could also be accentuated if the middle-ear is pressurized. Studies by Margolis, Saly, and Keefe (1999) and Keefe and Simmons (2003) have suggested that pressurizing the middle-ear allowed to correctly identify middle-ear pathology in participants whose middle ear statuses (using WAI) appeared to look normal at ambient pressure. Moreover, investigations averaging PA in a specific range of frequencies instead of 226 – 8000 Hz (which includes low and high frequencies) would provide higher frequency selectivity and potentially increase sensitivity of PA estimates in test performance. Future investigations should also investigate the utility of gender and ethnicity specific norms in increasing the predictive value of WT for identifying middle ear pathologies.   4.8 Reflectance Area Index (RAI) The reflectance area index (RAI) was measured by the HearID Mimosa Acoustics system and is the average reflectance (in %) over a frequency range specified by the user with the software. The current study calculated RAI over a range of 500 – 8000 Hz as it was the default range set in the HearID system. RAI is similar to WT without pressurization and might therefore be quite useful in infants under 7 months of age whose compliant ear canals and middle ears are modified under pressure loads thereby violating underlying assumptions for tympanometry (Vanderwarff, Georgantas, & Prieve, 2007) and rendering tympanometry unreliable in this age group (Onusko, 2004). RAI has some potential applications clinically due to its ease of interpretation and sensitivity to middle ear pathology due to high frequency selectivity. For instance, Piskorski et al. (1999) reported that WAI, particularly in the 2000 – 4000 Hz range, is a sensitive predictor of conductive hearing loss in group of children (N = 161 ears) when they used the presence and size of the air-bone gap as a gold standard for confirming middle ear pathology. Keefe et al. (1993) 152  has also suggested that the mid-frequency range may be most useful for clinical tests of middle ear function using WAI. Since the margin of error due to reliability is lowest in the middle frequencies, the RAI can be set to measure average reflectance in this region to improve detection of various middle ear pathologies. One such study has been done by Hunter et al. (2010) who found that RAI values calculated over 1-2 kHz, 1-4 kHz and 2 kHz were best at discriminating between the DPOAE pass and DPOAE refer group in the newborn population. Future studies should consider calculating RAI with frequency specificity to determine its viability in distinguishing specific middle ear pathologies.   There were no significant differences in RAI between genders, ethnicities, or ears much like mean PA in the mixed-model ANOVA for PA measurements at ambient pressure. This can be expected given the lack of frequency selectivity in the calculation of RAI in the default range of 500 – 8000 Hz. The fact that the current study showed that PA patterns in the Caucasians were high in the low frequencies and low in the high frequencies compared to the Chinese meant that averaging opposing values of PA values in the 500 – 8000 Hz range would lead to the cancellation of observed differences between groups at ambient pressure. Similarly, the fact that the current study showed a trend toward higher low frequency PA and significantly lower high frequency PA patterns in males compared to females meant that the addition of low and high values of PA in groups would cancel out observed differences between groups. RAI did not differ significantly between ears as expected as no such differences in PA or PR were found in this study. Future investigations should calculate RAI at low, middle, and high frequency bandwidths to better reflect differences between groups (e.g. genders, ethnicities, or normal versus pathological groups).  153   A clinically viable tool must exhibit good reliability or small test-retest differences. The results of the current study revealed that RAI differed significantly between trials. However, this difference was very slight and may stem from the fact that RAI was measured over such a large frequency range including low frequencies which may be subject to variability between trials due to physiological noise (from the wires). None the less, Trial 1 and Trial 2 differed by only 1.05% (RAI was 58.40% in trial 1and 57.75% in trial 2) which is not expected to be clinically significant when comparing a normal group with a pathological group. A difference of 1.05% between trials is likely much smaller than the difference between normal and pathological ears. Future studies should investigate RAI at smaller frequency bandwidths for different middle ear pathologies to determine the diagnostic value of estimations of RAI at these ranges.       4.9 Reflectance Phase Angle and Admittance Magnitude  4.9.1 Reflectance Phase Angle and Admittance Phase The review by Voss et al. (2013) had emphasized the need for a gold standard or data selection criteria that would identify measurements with both acoustic leaks and probes that were either blocked or pushed up against the edge of the canal. One suggestion included measuring phase angle of impedance which should be relatively flat with frequency, negative in most cases for frequencies below 500 Hz and impedance magnitudes should be within bounds. However, these bounds were not clearly identified and the authors stated that more research had to be done in 154  that regard. The current study measured reflectance phase angle, admittance phase and admittance magnitude in order to determine if they could be of use in identifying valid measurements.   The reflectance phase angle was measured by HearID (in units of rd/2 π) and admittance phase was measured by ReflWin (in degrees). Reflectance phase angle in the current study stayed relatively flat with frequency prior to decreasing to more negative values with frequency. This is consistent with Rosowski et al. (2012) who measured reflectance phase (in degrees) using the Mimosa Acoustics HearID system and found that the phase angle tended to decrease from 0 to more negative values as a function of frequency from 0 – 6000 Hz. Voss and Allen (1994) also found that the reflectance phase (in radians normalized by π) measured in 10 normal hearing young adults (ages 18 – 24 yrs) tended to decrease from 0 to more negative values with increments in frequency from 0 – 15 kHz.  These studies are consistent with Voss et al. (2013) who stated that phase angle of impedance should be relatively flat as a function of frequency and can become negative in most cases for frequencies below 500 Hz .   Admittance phase (measured by the Reflwin) in both genders and ethnicities in the current study was relatively flat with frequency prior to decreasing to a minimum at 6300 Hz and increasing to 8 kHz. This is consistent with Sanford and Feeney (2008) who found admittance phase (measured in degrees) at TPP revealed a general negatively directed monotonic shift from stiffness to mass controlled phase as frequency increased from 0.25 to 5 kHz and then shifted toward a positive direction out to 8 kHz. Keefe et al. (1993), Holte et al. (1991), Sanford and Feeney (2008) and the present study all consistently yielded   non-monotonic changes in 155  admittance phase as a function of frequency. This pattern may be related to ear canal and/or middle ear resonance effects possibly due to vibration of the ear-canal wall, TM, and/or middle ear characteristics. In addition, the phase function zero crossing, indicating equal contributions of outer and middle-ear compliance (+ phase) and mass (- phase) components near 4 kHz in adults (Sanford & Feeney, 2008). However, the larger adult ear-canal volume (resulting in increased compliance) and increased middle ear or ear-canal stiffness may also be contributing to the high frequency Y phase zero crossing in adults (Sanford & Feeney, 2008). The findings of this study do not generalize to predict that all groups with higher ear canal volumes (be it Caucasians compared to Chinese or males compared to females) may exhibit higher frequency admittance phase zero crossings. As seen in the current study, although Caucasian and male groups exhibited higher ECVs than females, they had lower frequency admittance phase zero crossings (Refer to Figure 22 and 23).      There have been no previous studies that have investigated the effect of gender and ethnicity on normative data for reflectance phase angle. However, given the effect of gender and ethnicity on PA measurements it can be expected that some differences will be observed between groups. Accordingly, this study found that mean reflectance phase angle values for females were significantly higher than males between 5578 – 5602 using HearID; likewise, they were higher in females compared to males between 4000 – 5000 Hz and lower at 8000 Hz using the ReflWin. There was a trend toward mean phase angle values being higher in the Chinese compared to the Caucasian group in the high frequencies using the HearID. This trend showed significance using the ReflWin system in which the Chinese group showed higher mean phase angle values between 4000 – 6300 Hz compared to Caucasians. Differences observed could be related to 156  differences in the cross-sectional area of the ear canal at the tympanic membrane and length of the ear canal in these populations as they influence calculations of group delay which is derived from reflectance phase angle (Rosowki et al., 2012). Thus, potentially larger cross-sectional areas of the ear canal at the tympanic membrane or longer ear canal length could explain lower reflectance phase angle values in the high frequencies in male and Caucasian groups as compared to female and Chinese groups.    As discussed previously, the reflectance phase angle provides information about how the wave is propagated in the ear across frequencies (Mimosa Acoustics, 2012). It is the phase of the reflected pressure relative to the incident pressure (Rosowki et al., 2012); it can also be used to estimate the length of time (group delay) it takes the incident wave to travel to the TM, the time associated with the reflected sound from the TM, and the time it takes for the reflected sound to return to the microphone (Rosowski et al., 2012). Rosowski et al. (2012) noted their normative sample exhibited a group delay of about 100 µs which when multiplied by the speed of sound in the ear canal (350 m/sec) yielded a length of about 3.5 cm. This length is about twice the distance between the probe tip and the tympanic membrane accounting for the forward travel of the incident wave and the backward travel of the reflection. Future studies should calculate group delay values to shed some light on whether the incident and reflected wave was propagated differently in various groups due to slight variation in ear canal size. Group delay is frequency dependent and influenced by the cross-sectional area of the ear canal at the tympanic membrane and ear canal length (Rosowski et al., 2012). This could potentially allow us to directly evaluate whether the ear canal size and geometry influences the propagation of the pressure wave in a way that would influence PA estimates in various groups (e.g. ethnicities, genders, individuals 157  with tympanic membrane perforations). It may also be useful clinically to identify middle ear pathologies which impact the ear-canal and tympanic membrane directly such as retraction of the tympanic membrane, tympanosclerosis, or cholesteotomas.   The phase of the pressure reflectance or reflectance phase angle is sensitive to the distance between the measurement location and the TM (Rosowki et al., 2012; Rosowski, Stenfelt, & Lilly, 2013). This suggests that normative data for reflectance phase values could also be valuable in identifying accurate WAI readings with appropriately oriented probes that have been adequately (deeply) inserted into the ear canal free of acoustic leaks. Further investigations are required to determine what reflectance phase patterns look like when the probe is not satisfactorily inserted into the ear.     4.9.2 Admittance Magnitude  Admittance magnitude (Y) is defined as the reciprocal of impedance (Mimosa Acoustics, 2012). In addition, it can be viewed as the velocity in the ear for a perfect pressure/force source and the ease with which a particular waveform moves through the middle ear (Mimosa Acoustics, 2012). Shahnaz and Bork (2006) chose admittance magnitude as an outcome variable in their study because it was thought to be comparable to tympanometric admittance.  Admittance magnitude (Y) was measured by the ReflWin Interacoustics system in the current study. Y was found to vary significantly by frequency in that it increased with frequency up to a maximum at 4 kHz prior to decreasing up to 8 kHz. This is consistent with previous literature which shows that Y 158  increases in magnitude as a function of frequency up to a maximal point after which it decreases as a function of frequency (Shahnaz & Bork, 2006; Sanford & Feeney, 2008).   In the current study, Caucasians demonstrated a pattern of higher Y at low frequencies (although not significant) and significantly lower Y at 8000 Hz compared to the Chinese. Males demonstrated higher Y values in the low to middle frequencies between 250 – 400 Hz and 1600 – 3150 Hz compared to females. These results are largely consistent with Shahnaz and Bork (2006) who also found similar differences in admittance magnitude between genders and ethnicities, but not between ears. Specifically, they found that males had higher Y values in the low to middle frequencies between 1781 and 2367 Hz compared to females and the Caucasian group had higher mean values from 211 to 1313 Hz. Their findings coincided with findings by Shahnaz and Davies (2006) which showed that mean compensated Ytm values obtained at probe tone frequencies between 226 - 900 Hz wee much lower in the Chinese group compared to the Caucasian group and those obtained up to 1120 Hz were much lower in females than males.  Larger body sizes are associated with lower middle ear compliance (Huang, Rosowski, & Peake, 2000), larger ear canal, and middle ear cavity sizes (Shahnaz & Bork, 2006) which could explain higher Y values in the low frequencies  where stiffness makes a significant contribution to impedance (Allen et al., 2005). In the current study, larger body sizes and ear canal volumes were observed in the Caucasian and male group compared to the Chinese and female group in the current study. It is likely that larger body sizes (indicated by BMI and ECV in this study) accounted for higher Y values in the Caucasian and male group compared to the Chinese and female group in this study.  159    As can be seen in Figure 4.20 and 4.21, the results of this study also show differences in Y between genders and ethnicities in the low frequencies (consistent with Shahnaz & Bork, 2006). However, only the differences between genders were significant in the low-mid frequencies while differences between ethnicities only showed a trend toward higher Y values in the low-mid frequencies. This is surprising given that the current study found differences between ethnicities at ambient and peak pressure in the low and high frequencies. Sanford and Feeney (2008) explained that admittance magnitude is affected by immittance qualities of the air space between probe and TM (unlike ER). It is possible that shallow insertions of the probe may have affected Y estimates more than PA estimates which are relatively stable and independent of location for much of the length of the ear canal (Voss et al., 2008). Furthermore, Shahnaz and Bork (2006) used the Mimosa Acoustics HearID system to calculate Y while the current study utilized the ReflWin Interacoustics system. Differences in calibration procedures may have led to differences in estimation of the pressure reflection coefficient resulting in differences in Y measures (Mimosa Acoustics, 2012). During the calibration procedure for the Reflwin system, the waveform characteristics at each frequency are measured for a small tube and a large tube so that the waveform characteristics of both tubes can be compared in order to separate the incident wave from the reflected wave (Keefe & Simmons, 2003). This procedure may be less accurate for lower frequencies because there are multiple reflections within the tube due to greater wavelengths for lower pitches (Shaw, 2009). That could explain why differences in Y measurements at the low frequencies weren’t captured for ethnicities using the ReflWin system as compared to the HearID system used by Shahnaz and Bork (2006). In addition, Y is dependent on the cross-sectional estimation of the ear canal which is calculated using constant values from 160  just two calibration cavities in the ReflWin system while being estimated using the size of the probe tip used for measurement by the HearID system (Sanford & Feeney, 2008). This means that ReflWin may have been less accurately able to tease out small differences between ethnicities than HearID in the low frequencies because it assumes a constant ear canal size.   4.10 Limitations and Future Directions There are several limitations of the study. It is known that there’s a decrease in stiffness of the middle ear as a function of age, resulting in the adult middle ear being more capable of efficient sound transmission in the lower frequencies compared to children (who have more efficient sound transmission in the higher frequencies). These findings are supported by histological and anatomical studies in humans which have documented age related middle ear changes. For instance, Ruah et al. (1991) have found that the tympanic membrane becomes less vascularized, less cellular, less elastic and more rigid with age and Harty (1953) report that ossicular joints in elderly patients contained less elastic tissue. However, little is known about the exact age at which these changes occur and impact PA measurements. Feeney et al. (2014) have documented significantly higher mean PA measurements for the middle age group (30 – 39 years) relative to both the young (20 – 29 years) and old age group (40-59 years) at frequencies between 0.5 – 1.6 kHz.  Including a sample of young adults with variable stiffness related changes in the middle ear due to variation in ages may result in smaller differences being observed in various groups (e.g. genders or ethnicities). Future studies should investigate potential differences in PA patterns as a function of age with smaller age ranges. It would also be beneficial to assess the utility of specific age ranges in improving the predictive value of WAI tests.   161  The RAI calculated between the defult range of 800 – 5000 Hz didn’t demonstrate any group differences (e.g. ethnicity or gender) due to the lack of frequency selectivity. Future investigations should calculate RAI at low, mid, and high frequency bands to determine the effect of gender and ethnicitiy at various bandwidths. A similar concept can also be applied to frequency-averaged PA measurements which were calculated only between 375 – 2000 Hz. RAI and frequency-averaged PA should also be calculated for groups with various types of middle ear pathologies to determine its predictive value for these conditions. These investigations would allow us to determine if ethnicity and gender specific norms for these values are warranted and whether these tests are diagnostically viable tools for identifying conductive hearing loss. Comments should also be made on ease of interpretation with different middle ear pathologies.  This study utilized PA measurements of surgically confirmed otoslcerotic ears from the HearID system to determine if instrument specific normative data (from the HearID system) would yield higher sensitivity and specificity. For the most part, instrument specific normative data did not increase test performance in identifying otosclerotic ears obtained from the HearID system. It is difficult to make gernalizations about whether instrument specific norms are warranted when only two frequencies were investigated. In addition, pathological ears were only obtained from the HearID system and composed of only surgically confirmed otosclerotic ears. Future investigations should calculate the sensitivity and specificity of instrument specific norms for a wider range of frequencies using normative and pathological data from all four systems to yield more reliable conclusions about whether instrument specific norms are warranted.   162  Anatomical variations in head size, height of the pinna, and distance from the lateral palpebral commissures to both the helical root and lobule have been demonstrated between genders (Brucker, Patel, & Sullivan, 2002). Differences in head shapes between Chinese and Caucasian groups have also been documented (Cooke & Wei, 1989; Le et al., 2002; Ball et al., 2010; Gu et al., 2011; Luximon, Ball, & Justice, 2012) indicating that they may also exhibit differences in ear canal diameter and cross-sectional area. Future studies should investigate the effects of such anatomical variations including cross-sectional area, ear canal length, and diameter of the ear between various groups (e.g. gender and ethnicity) on impedance measures.  These estimates may be more closely correlated with ear canal size allowing to better account for differences in impedance and PA estimates between groups. Other body size indices such as body fat percentage, lean body mass, and head circumference which may more closely reflect differences in size of the middle ear cavity, mass of soft tissue and conductive elements (e.g. mass of stapes, area of tympanic membrane etc.) should also be evaluated. Group delay could be derived from estimations of reflectance phase measurements to determine if the propagation of the incident and reflected wave was influenced by differences in the length of the ear canal, ear canal geometry, and cross-sectional area of the canal at the tympanic membrane between groups. Group delay might be associationed with differences between genders at frequencies from 4 – 6 kHz  as it is influenced by differences in ear canal geometry which have been demonstrated to be the source of non-uniformities in sound pressure across a canal cross-section at the measurement location (Rosowki, Stenfelt, & Lilly, 2013). In addition, measurements can be made at shallow and deep insertions of the probe to determine its effect on group delay. Group delay can be an accurate predictor of acoustics leaks as it reflects the time associated with the incoming and reflected pressure wave.  163   It is known that the impedance of middle ear which is used to derive PA is influenced by properties of reactance and resistance.  Below 800 Hz, impedance is due mostly to stiffness-based reactance (which is 10 times larger than resistance) resulting in only a small proportion of the incident power being absorbed into the middle ear (Puria & Allen, 1998; Allen et al., 2005) At frequencies below 1000 Hz, impedance is due to the stiffness of the tympanic membrane, middle ear volume, and most importantly the stiffness of the annular ligament (Lynch, Nedzelnitsy, & Peake, 1982). When pressure waves at these low frequencies reach the stapes, almost all of their power is briefly stored as potential energy in the stretched ligament and reflected. At higher frequencies above 6000 Hz, mass-based reactance of the ossicles becomes more important and the overall contribution of reactance is greater than resistance. It would be useful to measure reactance and resistance between ethnicities and genders to confirm if stiffness based reactance values are higher in Chinese group (that the Caucasian group) in the low frequencies and mass based reactance values are higher in the Caucasian group (than the Chinese group) in the high frequencies. It would shed some more insight on the reasons behind observed differences between groups.   When ASHA (1990) specified norms were used in a clinical study in Hong Kong up to 48% of Chinese children at various ages failing tympanometric screening were found misdiagnosed for middle ear pathology (Wan & Wong, 2002). This underscored the importance of utilizing the appropriate norms for a specific population in a clinical setting. Future investigations should investigate whether the sensitivity and specificity of gender and ethnicity specific norms are greatly increased for identifying various middle-ear pathologies.  164  Chapter 5: Conclusion  A set of normative PA data have been generated for a young adult sample of Chinese and Caucasian European descent between the ages of 18 and 34 years using four commercially available WAI devices (from Mimosa Acoustics, Inc. and Interacoustics, Inc.). The aim of the study was to facilitate the composition of a shared data repository of norms for clinical use as outlined by the Consensus Statement in the recent Eriksholm Workshop (Feeney et al., 2013). In this study, mean PA values differed significantly across frequencies between the four systems. However, differences between systems were not as great as differences between normal and otosclerotic ears obtained by Shahnaz et al. (2009). Instrument-specific norms may improve the predictive value of WAI testing using certain instruments for some middle ear pathologies, but not for the Mimosa Acoustics HearID system in this sample of otosclerotic ears. This indicates that instrument-specific norms are not essential when testing for Otosclerosis with the HearID system, but may prove to be useful using a larger frequency bin of analysis, for other systems or other middle ear pathologies. There were a few small significant differences between trials in the study consistent with the surrounding literature; however, these differences were not as great as those between normal and otosclerotic ears obtained by Shahnaz et al. (2009). This indicates that PA measurements have good test-retest reliability for diagnostic purposes. Mean PA differed significantly by gender and ethnicity. Differences in BMI and ECV which are associated with differences in ear canal size and middle ear cavity accounted for the observed variation in PA between ethnicities especially in the low frequencies. Mean PA values were higher at low frequencies and lower at high frequencies at peak pressure compared to ambient pressure. The change in measurement at peak pressure in comparison to ambient pressure is attributed to the 165  stiffening of the tympanic membrane and middle ear which occurs with pressurization. In addition, performing WAI measurements at TPP served to better reflect differences between genders and ethnicities at a broader range of frequencies compared to measurements at ambient pressure.   BMI and ECV were investigated as continuous covariates in predicting differences in PA across frequencies between ethnicities and genders. BMI and ECV were indicators of body size which accounted for differences between ethnicities especially in the low to middle frequencies, but not between genders. The potential source of differences in PA observed between ethnicities could be explained by BMI and ECV as they may be correlated to differences in ear canal size, cross-sectional area of the ear canal, and middle ear volume between ethnicities (Shahnaz & Bork, 2006). A study of the middle ears in exotic cat species found that the compliance of the middle ear cavity increases with body size (Huang, Rosowski, & Peake, 2000). This indicates that higher body sizes (indicated by higher BMI and ECV) in Caucasians may be associated lower stiffness of the middle ear transmission system explaining higher PA in this group compared to the Chinese group in the low to mid frequencies (Allen et al., 2005). The differences between genders (which occurred significantly in the high frequencies at ambient pressure) may be more highly correlated to other body size indices such as head size, circumference of the head in the saggital and frontal plane, cross-sectional area of the ear canal, ear canal diameter, and ear canal length (Voss et al., 2013; Keefe et al., 1993).  These factors should be investigated in future studies to determine if they better represent differences between genders.   166  This study also obtained normative data for frequency-averaged power absorbance (between 375 – 2000 Hz) using WT. WT is promising as it may potentially be easy to interpret (given that it has been demonstrated to produce single peaked tympanograms between 375 and 2000 Hz), less influenced by noise, and offer more predictive value in identifying conductive disorders than traditional 226 Hz tympanometry in adults and 1000 Hz tympanometry in infants (Titan Interacoustics, 2013; Sanford et al., 2009; Keefe & Simmons, 2003; Pikorski et al., 1999).  This study found that positive and negative pressure levels relative to the TPP led to decreases in frequency-averaged PA in a pattern identical to traditional 226 Hz tympanometry. Females had lower frequency averaged PA values compared to males. Caucasians had higher frequency averaged PA values compared to the Chinese. These results are consistent with previous studies which have documented differences due to gender and ethnicity on normative data on WAI (at ambient and peak pressure) and 226 Hz tympanometry. The smaller middle ear cavities and ear canal sizes associated with Chinese and female groups are thought to be indicative of more stiffness based middle ear transmission systems (Huang, Rosowski, & Peake, 2000) resulting in lower  PA averaged in the low-mid frequencies where stiffness makes a greater contribution to impedance (Allen et al., 2005). It is interesting to note that WT was better able to reflect the magnitude of differences between ethnicities and genders than both WAI at ambient and peak pressure. Future research should investigate the clinical utility of WT in more clearly identifying differences between normal and pathological group. Currently it is set by Titan Interacoustics to measure middle ear status between 375 – 2000 Hz in order to create single peaked tympanograms which are easy to interpret. However, it would be even more beneficial if the frequency bandwidth could be modified by the experienced Clinician or researcher in order to increase its sensitivity to certain middle ear pathologies.   167  The reflectance area index (RAI) is the average reflectance (in %) over a frequency range specified by the user with the software. The current study calculated RAI over a range of 500 – 8000 Hz. RAI is similar to WT without pressurization and might therefore be quite useful in infants under 7 months of age whose compliant ear canals and middle ears are modified under pressure loads thereby violating underlying assumptions for tympanometry (Vanderwarff, Georgantas, & Prieve, 2007) and rendering tympanometry unreliable in this age group (Onusko, 2004). RAI has some potential applications clinically due to its ease of interpretation and sensitivity to middle ear pathology (Hunter et al., 2010). However, since the RAI was calculated over such a wide frequency range of 500 – 8000 Hz in this study, no differences between groups were found since each group (male, female, Chinese, and Caucasian) exhibits opposing patterns of PA in the low and high frequencies which average out resulting in similar PA values between genders and ethnicities. Future investigations should calculate RAI in low, middle, and high frequency bandwidths to assess its potential diagnostic utility.   Admittance magnitude (Y) is defined as the reciprocal of impedance (Mimosa Acoustics, 2012). In the current study, Caucasians demonstrated a pattern of higher Y compared to the Chinese at low frequencies and significantly lower Y at 8000 Hz. Males demonstrated higher Y values in the low to middle frequencies between 250 – 400 Hz and 1600 – 3150 Hz compared to females. These results are consistent with literature related to 226 Hz tympanometry and WAI. Higher body sizes and ear canal volumes were observed in the Caucasian and male group compared to the Chinese and female group in the current study. Larger body sizes in the Caucasian and male group are associated with lower stiffness dominated middle ear transmission systems (Huang, Rosowski, & Peake, 2000), larger ear canal, and middle ear cavity sizes (Shahnaz & Bork, 2006) 168  which could potentially account for higher Y values in the low frequencies where stiffness makes a significant contribution to impedance (Allen et al., 2005).   The reflectance phase angle and admittance phase tended to be higher in the high frequencies for female and Chinese groups compared to male and Cauacasian groups. Differences observed could be related to differences in the cross-sectional area of the ear canal at the tympanic membrane and length of the ear canal in these populations (Rosowki et al., 2012). The reflectance phase angle provides information about how the wave is propagated in the ear across frequencies (Mimosa Acoustics, 2012). It is the phase of the reflected pressure relative to the incident pressure (Rosowki et al., 2012). The reflectance phase angle is also sensitive to the distance between the measurement location and the TM (Rosowki et al., 2012). This suggests that normative data for reflectance phase values could be valuable in identifying accurate WAI readings with appropriately oriented probes that have been adequately (deeply) inserted into the ear canal free of acoustic leaks. It can also be used to calculate group delay to reflect differences in between groups due to ear canal geometry and ear canal cross-sectional area which may influence the propagation of the pressure wave from the measurement location to the TM (Rosowki, Stenfelt, & Lilly, 2013).       169  Bibliography  Allen, J., Jeng, P., and Levitt, H. (2005). 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Chinese	Group	 Caucasian	Group		 Mean	 	 Median	 	 Max	upper	range		Min	lower	range		Mean	 	 Median	 	 Max	upper	range	Min	lower	range			 Male	 Female	 Male	 Female	 Male	 Female	 Male	 Female	 Male	 Female	 Male	 Female	 Male	 Female	 Male	 Female	Age	(Years)	24.95	 23.79	 24.00	 23.00	 32.00	 34.00	 18.00	 18.00	 25.60	 23.32	 26.00	 22.00	 35.00	 31.00	 18.00	 18.00		B.M.I	 23.41	 20.23	 22.03	 19.70	 36.90	 24.00	 17.30	 18.1	 23.21	 22.49	 22.30	 23.03	 31.30	 27.02	 15.70	 18.60	     A.2 Descriptive Statistics for Power Absorbance Mean, median, standard deviation, 5th – 95th percentile, maximum, and minimum power absorbance values listed across frequencies and grouped by trials, gender, ethnicity, and system at ambient and peak tympanometric pressure conditions.  186  PA	Ambient	PressureFrequency	(Hz)Trial	1 Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female250 0.09 0.07 0.05 0.030.04-0.16 0.02-0.11 0.08 0.07 0.31 0.12 0.03 0.02 0.13 0.09 0.07 0.050.03-0.24 0.04-0.16 0.11 0.08 0.35 0.31 0.02 0.03 0.05 0.04 0.04 0.040.00-0.11 0.00-0.10 0.05 0.03 0.17 0.22 0.00 0.00 0.06 0.04 0.14 0.040.00-0.15 0.00-0.13 0.03 0.02 0.84 0.14 0.00 0.00 0.06 0.05 0.03 0.050.02-0.11 0.00-0.10 0.06 0.04 0.18 0.27 0.00 0 0.06 0.06 0.03 0.030.03-0.11 0.02-0.11 0.05 0.06 0.17 0.18 0.01 0.00 0.12 0.08 0.07 0.040.04-0.22 0.02-0.13 0.12 0.09 0.40 0.16 0.03 0.01 0.14 0.12 0.04 0.070.07-0.21 0.04-0.22 0.13 0.12 0.21 0.40 0.06 0.03315 0.09 0.05 0.05 0.030.02-0.17 0.01-0.10 0.08 0.05 0.32 0.10 0.02 0.01 0.13 0.09 0.08 0.050.03-0.26 0.02-0.17 0.10 0.08 0.38 0.32 0.02 0.02 0.08 0.07 0.05 0.050.01-0.15 0.01-0.15 0.08 0.06 0.26 0.26 0.01 0.00 0.10 0.07 0.13 0.050.02-0.21 0.01-0.17 0.07 0.04 0.83 0.20 0.01 0.00 0.08 0.07 0.04 0.050.03-0.14 0.01-0.14 0.08 0.06 0.25 0.27 0.01 0.00 0.09 0.08 0.05 0.040.03-0.17 0.03-0.14 0.08 0.08 0.26 0.25 0.02 0.01 0.12 0.08 0.08 0.040.03-0.23 0.01-0.13 0.12 0.08 0.42 0.17 0.02 0.01 0.15 0.12 0.05 0.080.06-0.23 0.03-0.23 0.15 0.12 0.24 0.42 0.04 0.02400 0.09 0.06 0.07 0.040.02-0.20 0.01-0.12 0.08 0.06 0.35 0.13 0.01 0.00 0.14 0.09 0.09 0.070.01-0.31 0.02-0.20 0.12 0.08 0.39 0.35 0.00 0.01 0.12 0.11 0.06 0.070.04-0.19 0.02-0.24 0.11 0.10 0.38 0.32 0.01 0.01 0.15 0.11 0.13 0.070.05-0.33 0.02-0.25 0.13 0.09 0.82 0.30 0.01 0.01 0.12 0.11 0.06 0.080.04-0.21 0.02-0.22 0.11 0.10 0.37 0.39 0.02 0.01 0.13 0.12 0.07 0.060.05-0.24 0.04-0.21 0.12 0.11 0.33 0.37 0.01 0.02 0.16 0.10 0.09 0.050.05-0.30 0.02-0.18 0.15 0.11 0.44 0.23 0.02 0.01 0.19 0.16 0.07 0.090.08-0.28 0.05-0.30 0.20 0.15 0.32 0.44 0.06 0.02500 0.16 0.12 0.09 0.060.05-0.33 0.04-0.22 0.14 0.12 0.40 0.27 0.03 0.02 0.24 0.16 0.13 0.090.06-0.45 0.05-0.33 0.21 0.14 0.54 0.40 0.03 0.03 0.19 0.17 0.09 0.10.07-0.33 0.05-0.33 0.17 0.16 0.58 0.50 0.04 0.04 0.25 0.18 0.15 0.10.10-0.53 0.05-0.40 0.22 0.18 0.83 0.45 0.01 0.05 0.18 0.17 0.09 0.110.06-0.33 0.04-0.30 0.17 0.16 0.56 0.57 0.04 0.03 0.22 0.18 0.11 0.090.09-0.39 0.06-0.33 0.19 0.17 0.53 0.56 0.01 0.04 0.23 0.16 0.10 0.070.09-0.38 0.04-0.28 0.23 0.17 0.46 0.32 0.06 0.03 0.29 0.23 0.09 0.10.14-0.43 0.09-0.38 0.29 0.23 0.49 0.46 0.10 0.06630 0.24 0.18 0.12 0.080.07-0.46 0.07-0.32 0.22 0.18 0.56 0.39 0.06 0.04 0.34 0.24 0.16 0.120.10-0.60 0.07-0.46 0.32 0.22 0.74 0.56 0.07 0.06 0.28 0.24 0.13 0.130.11-0.47 0.08-0.40 0.25 0.22 0.81 0.80 0.08 0.06 0.38 0.29 0.18 0.130.19-0.72 0.12-0.52 0.34 0.30 0.86 0.58 0.08 0.09 0.27 0.25 0.13 0.150.10-0.48 0.07-0.39 0.25 0.22 0.80 0.91 0.07 0.06 0.35 0.27 0.14 0.130.19-0.59 0.10-0.48 0.32 0.25 0.71 0.80 0.09 0.07 0.32 0.24 0.11 0.10.15-0.51 0.08-0.40 0.31 0.23 0.53 0.44 0.11 0.07 0.40 0.32 0.13 0.110.21-0.57 0.15-0.51 0.41 0.31 0.70 0.53 0.16 0.11800 0.31 0.26 0.17 0.130.08-0.58 0.06-0.48 0.29 0.28 0.83 0.62 0.03 0.04 0.42 0.31 0.18 0.170.13-0.69 0.08-0.58 0.42 0.29 0.76 0.83 0.06 0.03 0.37 0.34 0.15 0.140.16-0.64 0.13-0.51 0.35 0.33 0.94 0.82 0.13 0.09 0.46 0.40 0.19 0.150.23-0.77 0.21-0.70 0.42 0.36 0.90 0.73 0.17 0.13 0.38 0.35 0.15 0.150.16-0.64 0.12-0.55 0.35 0.33 0.95 0.82 0.13 0.09 0.45 0.38 0.16 0.150.22-0.74 0.16-0.64 0.43 0.35 0.79 0.95 0.18 0.13 0.42 0.33 0.15 0.140.18-0.65 0.10-0.54 0.41 0.34 0.71 0.59 0.13 0.08 0.50 0.42 0.13 0.150.30-0.69 0.18-0.65 0.50 0.41 0.71 0.71 0.24 0.131000 0.38 0.37 0.18 0.160.13-0.64 0.10-0.60 0.33 0.38 0.94 0.64 0.00 0.05 0.50 0.38 0.18 0.180.19-0.78 0.13-0.64 0.51 0.33 0.87 0.94 0.09 0.00 0.44 0.44 0.13 0.140.24-0.62 0.22-0.61 0.43 0.44 0.82 0.69 0.21 0.14 0.51 0.51 0.17 0.160.23-0.80 0.33-0.79 0.49 0.49 0.94 0.91 0.20 0.21 0.45 0.45 0.13 0.140.23-0.63 0.21-0.65 0.44 0.44 0.83 0.71 0.22 0.14 0.52 0.45 0.15 0.130.24-0.75 0.23-0.63 0.50 0.44 0.82 0.83 0.20 0.22 0.51 0.44 0.15 0.160.26-0.72 0.14-0.70 0.53 0.46 0.77 0.72 0.20 0.13 0.59 0.51 0.11 0.150.37-0.77 0.26-0.72 0.60 0.53 0.80 0.77 0.36 0.201250 0.47 0.44 0.15 0.120.26-0.72 0.21-0.63 0.45 0.46 0.77 0.67 0.05 0.15 0.55 0.47 0.14 0.150.34-0.81 0.26-0.72 0.55 0.45 0.86 0.77 0.18 0.05 0.49 0.49 0.12 0.130.29-0.67 0.29-0.72 0.50 0.49 0.73 0.73 0.28 0.26 0.55 0.58 0.15 0.140.31-0.77 0.34-0.81 0.53 0.57 0.92 0.86 0.21 0.27 0.51 0.50 0.12 0.120.34-0.69 0.31-0.73 0.51 0.51 0.73 0.76 0.29 0.29 0.55 0.51 0.14 0.120.32-0.78 0.34-0.69 0.54 0.51 0.87 0.73 0.20 0.29 0.60 0.53 0.12 0.130.40-0.74 0.28-0.72 0.59 0.54 0.82 0.74 0.37 0.27 0.64 0.60 0.09 0.120.50-0.79 0.40-0.74 0.63 0.59 0.85 0.82 0.47 0.371600 0.52 0.50 0.13 0.160.35-0.72 0.26-0.76 0.52 0.49 0.76 0.85 0.31 0.20 0.59 0.52 0.13 0.130.39-0.78 0.35-0.72 0.58 0.52 0.81 0.76 0.25 0.31 0.54 0.52 0.12 0.150.33-0.69 0.30-0.73 0.57 0.52 0.75 0.75 0.29 0.13 0.59 0.59 0.13 0.130.38-0.73 0.40-0.80 0.60 0.58 0.85 0.90 0.21 0.29 0.56 0.53 0.12 0.150.35-0.73 0.31-0.73 0.58 0.54 0.75 0.78 0.28 0.13 0.59 0.56 0.13 0.120.35-0.73 0.35-0.73 0.61 0.58 0.74 0.75 0.22 0.28 0.62 0.56 0.09 0.140.45-0.75 0.31-0.75 0.63 0.57 0.77 0.77 0.40 0.27 0.65 0.62 0.09 0.090.53-0.75 0.45-0.75 0.66 0.63 0.92 0.77 0.50 0.402000 0.60 0.54 0.13 0.150.37-0.77 0.29-0.75 0.61 0.57 0.83 0.79 0.34 0.21 0.62 0.60 0.12 0.130.46-0.82 0.37-0.77 0.64 0.61 0.87 0.83 0.36 0.34 0.64 0.58 0.12 0.150.42-0.81 0.36-0.75 0.63 0.61 0.93 0.84 0.39 0.16 0.63 0.64 0.11 0.120.46-0.79 0.50-0.88 0.65 0.62 0.86 0.93 0.29 0.45 0.65 0.58 0.12 0.140.44-0.86 0.35-0.76 0.63 0.61 0.98 0.84 0.39 0.16 0.62 0.65 0.11 0.120.43-0.79 0.44-0.86 0.64 0.63 0.86 0.98 0.30 0.39 0.66 0.58 0.12 0.140.43-0.83 0.35-0.75 0.67 0.60 0.89 0.79 0.40 0.29 0.64 0.66 0.11 0.120.50-0.82 0.43-0.83 0.63 0.67 0.98 0.89 0.39 0.402500 0.74 0.66 0.15 0.130.46-0.94 0.46-0.86 0.78 0.67 0.97 0.91 0.45 0.42 0.72 0.74 0.11 0.150.55-0.89 0.46-0.94 0.71 0.78 0.93 0.97 0.50 0.45 0.71 0.64 0.12 0.140.55-0.92 0.46-0.83 0.69 0.64 0.99 0.93 0.41 0.32 0.70 0.74 0.09 0.10.56-0.83 0.61-0.92 0.71 0.72 0.87 0.98 0.48 0.59 0.71 0.64 0.12 0.140.57-0.90 0.45-0.87 0.69 0.63 1.00 0.94 0.53 0.31 0.68 0.71 0.10 0.120.52-0.83 0.57-0.90 0.70 0.69 0.86 1.00 0.48 0.53 0.76 0.67 0.14 0.130.53-0.96 0.49-0.85 0.77 0.69 0.97 0.92 0.45 0.43 0.71 0.76 0.10 0.140.57-0.86 0.53-0.96 0.71 0.77 0.94 0.97 0.55 0.453150 0.77 0.76 0.15 0.130.49-0.97 0.55-0.95 0.80 0.78 0.99 0.96 0.46 0.47 0.73 0.77 0.12 0.150.56-0.92 0.49-0.97 0.73 0.80 0.96 0.99 0.50 0.46 0.74 0.71 0.11 0.140.60-0.90 0.48-0.92 0.74 0.70 0.97 0.95 0.53 0.38 0.72 0.77 0.10 0.090.58-0.88 0.62-0.92 0.71 0.76 0.92 0.99 0.49 0.58 0.74 0.70 0.11 0.150.61-0.93 0.47-0.94 0.73 0.68 0.97 0.97 0.58 0.34 0.72 0.74 0.12 0.110.57-0.88 0.61-0.93 0.72 0.73 0.92 0.97 0.24 0.58 0.74 0.72 0.16 0.140.52-0.96 0.49-0.95 0.73 0.74 0.98 0.98 0.40 0.42 0.65 0.74 0.12 0.160.47-0.83 0.52-0.96 0.64 0.73 0.89 0.98 0.32 0.404000 0.72 0.81 0.15 0.120.47-0.93 0.63-0.96 0.75 0.80 0.98 0.97 0.45 0.48 0.66 0.72 0.12 0.150.45-0.85 0.47-0.93 0.65 0.75 0.88 0.98 0.35 0.45 0.71 0.75 0.15 0.180.51-0.93 0.39-0.94 0.72 0.77 0.98 0.97 0.29 0.22 0.66 0.72 0.15 0.130.46-0.88 0.50-0.90 0.64 0.73 0.95 0.94 0.32 0.41 0.71 0.74 0.15 0.190.50-0.93 0.39-0.94 0.71 0.76 0.98 0.98 0.23 0.22 0.67 0.71 0.17 0.150.48-0.90 0.50-0.93 0.68 0.71 0.95 0.98 0.00 0.23 0.66 0.77 0.18 0.120.40-0.93 0.59-0.95 0.65 0.77 0.98 0.98 0.38 0.44 0.55 0.66 0.16 0.180.37-0.80 0.40-0.93 0.53 0.65 0.84 0.98 0.00 0.385000 0.58 0.69 0.14 0.130.37-0.79 0.47-0.87 0.55 0.69 0.97 0.93 0.30 0.40 0.45 0.58 0.11 0.140.32-0.65 0.37-0.79 0.43 0.55 0.72 0.97 0.22 0.30 0.58 0.69 0.22 0.210.15-0.86 0.33-0.94 0.59 0.73 0.99 0.98 0.04 0.08 0.50 0.54 0.17 0.240.23-0.76 0.12-0.84 0.54 0.56 0.78 0.93 0.10 0.00 0.58 0.69 0.21 0.210.23-0.87 0.37-0.96 0.60 0.73 0.99 0.98 0.01 0.15 0.52 0.58 0.19 0.210.24-0.77 0.23-0.87 0.56 0.60 0.93 0.99 0.02 0.01 0.54 0.63 0.16 0.140.34-0.84 0.38-0.83 0.53 0.68 0.93 0.86 0.27 0.27 0.39 0.54 0.12 0.160.25-0.61 0.34-0.84 0.39 0.53 0.73 0.93 0.00 0.276300 0.42 0.46 0.12 0.120.21-0.58 0.27-0.64 0.41 0.44 0.69 0.72 0.16 0.23 0.34 0.42 0.12 0.120.13-0.49 0.21-0.58 0.36 0.41 0.65 0.69 0.10 0.16 0.47 0.59 0.21 0.170.10-0.74 0.32-0.81 0.48 0.61 0.98 0.98 0.00 0.21 0.38 0.39 0.18 0.230.13-0.71 0.01-0.67 0.36 0.46 0.82 0.93 0.10 0.00 0.39 0.48 0.20 0.170.07-0.64 0.24-0.71 0.39 0.44 0.89 0.90 0.00 0.09 0.28 0.39 0.14 0.20.11-0.51 0.07-0.64 0.25 0.39 0.61 0.89 0.06 0.00 0.40 0.43 0.15 0.150.16-0.64 0.18-0.64 0.39 0.45 0.68 0.72 0.01 0.12 0.30 0.40 0.11 0.150.11-0.41 0.16-0.64 0.30 0.39 0.56 0.68 0.00 0.018000 0.44 0.40 0.16 0.160.24-0.77 0.22-0.76 0.41 0.36 0.89 0.81 0.17 0.13 0.36 0.44 0.14 0.160.10-0.58 0.24-0.77 0.37 0.41 0.72 0.89 0.08 0.17 0.28 0.28 0.21 0.180.00-0.64 0.00-0.50 0.26 0.32 0.67 0.63 0.00 0.00 0.15 0.28 0.14 0.210.00-0.36 0.00-0.64 0.11 0.26 0.57 0.67 0.00 0.00 0.34 0.31 0.18 0.170.08-0.66 0.06-0.58 0.28 0.29 0.79 0.79 0.00 0.05 0.23 0.34 0.15 0.180.00-0.48 0.08-0.66 0.21 0.28 0.53 0.79 0.00 0.00Trial	2250 0.11 0.07 0.06 0.030.04-0.20 0.03-0.12 0.10 0.06 0.34 0.16 0.03 0.02 0.13 0.11 0.06 0.060.03-0.23 0.04-0.20 0.11 0.10 0.26 0.34 0.01 0.03 0.05 0.04 0.03 0.040.01-0.10 0.00-0.11 0.04 0.04 0.11 0.17 0.00 0.00 0.07 0.04 0.13 0.040.00-0.14 0.00-0.10 0.04 0.03 0.83 0.13 0.00 0.00 0.07 0.06 0.03 0.050.01-0.12 0.00-0.16 0.07 0.04 0.17 0.21 0.01 0.00 0.06 0.07 0.04 0.030.01-0.12 0.01-0.12 0.05 0.07 0.21 0.17 0.00 0.01 0.13 0.08 0.06 0.040.04-0.24 0.02-0.13 0.12 0.09 0.35 0.16 0.04 0.02 0.14 0.13 0.05 0.060.08-0.23 0.04-0.24 0.14 0.12 0.24 0.35 0.07 0.04315 0.11 0.06 0.07 0.030.03-0.21 0.01-0.12 0.10 0.05 0.33 0.15 0.02 0.01 0.13 0.11 0.07 0.070.03-0.24 0.03-0.21 0.12 0.10 0.25 0.33 0.01 0.02 0.08 0.07 0.04 0.050.02-0.13 0.01-0.16 0.08 0.07 0.21 0.20 0.00 0.00 0.10 0.06 0.13 0.050.02-0.21 0.00-0.17 0.07 0.06 0.83 0.19 0.01 0.00 0.10 0.08 0.05 0.060.02-0.17 0.00-0.22 0.10 0.07 0.24 0.23 0.01 -0.01 0.09 0.10 0.05 0.050.03-0.15 0.02-0.17 0.08 0.10 0.27 0.24 0.00 0.01 0.13 0.07 0.07 0.040.03-0.27 0.01-0.13 0.12 0.08 0.35 0.17 0.02 0.01 0.16 0.13 0.06 0.070.07-0.27 0.03-0.27 0.14 0.12 0.29 0.35 0.05 0.02400 0.12 0.07 0.08 0.050.03-0.25 0.01-0.15 0.11 0.07 0.36 0.19 0.02 0.01 0.15 0.12 0.09 0.080.01-0.28 0.03-0.25 0.15 0.11 0.30 0.36 0.00 0.02 0.12 0.11 0.05 0.070.04-0.20 0.02-0.24 0.11 0.11 0.31 0.32 0.02 0.01 0.15 0.11 0.13 0.070.03-0.32 0.03-0.27 0.13 0.08 0.83 0.29 0.03 0.01 0.13 0.12 0.06 0.080.05-0.19 0.02-0.26 0.13 0.11 0.34 0.37 0.02 0.00 0.14 0.13 0.07 0.060.03-0.23 0.05-0.19 0.13 0.13 0.40 0.34 0.02 0.02 0.16 0.10 0.08 0.050.04-0.33 0.02-0.18 0.15 0.11 0.39 0.23 0.04 0.01 0.21 0.16 0.08 0.080.10-0.35 0.04-0.33 0.19 0.15 0.38 0.39 0.06 0.04500 0.19 0.13 0.10 0.070.06-0.37 0.04-0.26 0.18 0.12 0.43 0.26 0.05 0.04 0.25 0.19 0.13 0.10.04-0.41 0.06-0.37 0.25 0.18 0.49 0.43 0.01 0.05 0.19 0.18 0.08 0.10.10-0.36 0.04-0.34 0.17 0.16 0.49 0.47 0.04 0.04 0.24 0.18 0.15 0.10.08-0.50 0.07-0.38 0.23 0.16 0.83 0.44 0.04 0.03 0.20 0.17 0.09 0.110.10-0.32 0.03-0.34 0.18 0.15 0.52 0.55 0.03 0.00 0.23 0.20 0.11 0.090.07-0.40 0.10-0.32 0.21 0.18 0.59 0.52 0.05 0.03 0.23 0.16 0.09 0.070.09-0.40 0.05-0.28 0.23 0.16 0.44 0.32 0.08 0.04 0.30 0.23 0.11 0.090.17-0.48 0.09-0.40 0.29 0.23 0.56 0.44 0.11 0.08630 0.27 0.20 0.13 0.10.09-0.50 0.06-0.39 0.25 0.18 0.55 0.43 0.06 0.06 0.36 0.27 0.18 0.130.07-0.66 0.09-0.50 0.35 0.25 0.72 0.55 0.03 0.06 0.29 0.26 0.12 0.130.17-0.47 0.07-0.49 0.25 0.24 0.72 0.71 0.08 0.06 0.36 0.28 0.17 0.130.14-0.67 0.13-0.51 0.36 0.26 0.84 0.60 0.09 0.06 0.30 0.26 0.13 0.150.17-0.54 0.06-0.46 0.28 0.24 0.75 0.85 0.07 0.03 0.36 0.30 0.16 0.130.13-0.67 0.17-0.54 0.34 0.28 0.74 0.75 0.09 0.07 0.32 0.23 0.10 0.10.14-0.47 0.09-0.40 0.31 0.24 0.50 0.44 0.13 0.06 0.41 0.32 0.14 0.10.25-0.65 0.14-0.47 0.41 0.31 0.70 0.50 0.16 0.13800 0.33 0.30 0.16 0.150.10-0.64 0.07-0.54 0.33 0.30 0.74 0.65 0.03 0.04 0.44 0.33 0.19 0.160.09-0.72 0.10-0.64 0.45 0.33 0.73 0.74 0.00 0.03 0.38 0.37 0.14 0.160.23-0.64 0.12-0.62 0.35 0.35 0.92 0.89 0.13 0.08 0.45 0.39 0.18 0.160.21-0.75 0.20-0.62 0.42 0.35 0.86 0.86 0.19 0.11 0.41 0.38 0.15 0.170.23-0.63 0.11-0.63 0.36 0.37 0.94 0.88 0.13 0.08 0.45 0.41 0.17 0.150.21-0.73 0.23-0.63 0.41 0.36 0.79 0.94 0.19 0.13 0.41 0.32 0.14 0.140.20-0.63 0.11-0.54 0.41 0.33 0.70 0.61 0.15 0.06 0.51 0.41 0.15 0.140.28-0.72 0.20-0.63 0.50 0.41 0.83 0.70 0.24 0.151000 0.40 0.40 0.16 0.170.14-0.63 0.10-0.65 0.43 0.41 0.66 0.67 0.06 0.04 0.50 0.40 0.17 0.160.17-0.72 0.14-0.63 0.55 0.43 0.80 0.66 0.05 0.06 0.46 0.47 0.12 0.150.31-0.65 0.20-0.69 0.46 0.48 0.84 0.70 0.21 0.13 0.52 0.50 0.18 0.160.27-0.85 0.28-0.81 0.48 0.48 0.88 0.84 0.23 0.21 0.48 0.47 0.13 0.160.33-0.65 0.19-0.71 0.48 0.47 0.84 0.82 0.21 0.13 0.53 0.48 0.17 0.130.28-0.83 0.33-0.65 0.51 0.48 0.88 0.84 0.24 0.21 0.50 0.43 0.15 0.160.23-0.71 0.14-0.70 0.51 0.45 0.80 0.72 0.22 0.12 0.58 0.50 0.13 0.150.35-0.77 0.23-0.71 0.60 0.51 0.82 0.80 0.29 0.221250 0.49 0.47 0.14 0.140.24-0.68 0.22-0.69 0.50 0.48 0.74 0.77 0.17 0.16 0.55 0.49 0.14 0.140.29-0.75 0.24-0.68 0.56 0.50 0.82 0.74 0.22 0.17 0.52 0.49 0.11 0.130.34-0.70 0.30-0.71 0.54 0.50 0.72 0.74 0.32 0.27 0.56 0.57 0.16 0.120.32-0.88 0.37-0.76 0.53 0.58 0.95 0.82 0.32 0.31 0.53 0.49 0.11 0.120.34-0.68 0.32-0.70 0.51 0.50 0.83 0.75 0.33 0.27 0.56 0.53 0.16 0.110.33-0.85 0.34-0.68 0.53 0.51 0.95 0.83 0.31 0.33 0.59 0.52 0.12 0.140.39-0.77 0.28-0.72 0.60 0.53 0.81 0.74 0.32 0.27 0.62 0.59 0.10 0.120.49-0.77 0.39-0.77 0.62 0.60 0.83 0.81 0.37 0.321600 0.55 0.51 0.14 0.150.34-0.74 0.28-0.74 0.57 0.51 0.86 0.80 0.32 0.23 0.58 0.55 0.12 0.140.37-0.76 0.34-0.74 0.59 0.57 0.78 0.86 0.29 0.32 0.58 0.54 0.10 0.150.40-0.71 0.30-0.74 0.59 0.56 0.74 0.81 0.32 0.15 0.59 0.60 0.13 0.130.39-0.76 0.42-0.82 0.59 0.58 0.97 0.86 0.35 0.32 0.59 0.54 0.11 0.160.40-0.74 0.29-0.76 0.60 0.56 0.81 0.82 0.32 0.15 0.59 0.59 0.12 0.110.40-0.73 0.40-0.74 0.60 0.60 0.97 0.81 0.36 0.32 0.62 0.55 0.09 0.140.42-0.73 0.32-0.75 0.63 0.57 0.77 0.77 0.41 0.25 0.63 0.62 0.09 0.090.51-0.76 0.42-0.73 0.63 0.63 0.78 0.77 0.46 0.412000 0.60 0.52 0.12 0.140.35-0.77 0.25-0.71 0.59 0.51 0.87 0.76 0.32 0.19 0.60 0.60 0.14 0.120.41-0.79 0.35-0.77 0.61 0.59 0.94 0.87 0.30 0.32 0.64 0.59 0.12 0.150.46-0.82 0.36-0.79 0.62 0.61 0.95 0.87 0.41 0.17 0.64 0.66 0.09 0.120.50-0.80 0.50-0.88 0.65 0.65 0.89 0.91 0.46 0.48 0.66 0.59 0.12 0.150.45-0.92 0.35-0.78 0.63 0.62 0.97 0.88 0.42 0.16 0.64 0.66 0.09 0.120.48-0.74 0.45-0.92 0.64 0.63 0.87 0.97 0.44 0.42 0.65 0.58 0.11 0.140.44-0.80 0.34-0.76 0.65 0.62 0.88 0.78 0.38 0.30 0.63 0.65 0.10 0.110.48-0.79 0.44-0.80 0.63 0.65 0.90 0.88 0.46 0.382500 0.72 0.65 0.14 0.120.50-0.95 0.47-0.89 0.72 0.67 0.97 0.90 0.47 0.37 0.70 0.72 0.12 0.140.52-0.89 0.50-0.95 0.69 0.72 0.99 0.97 0.50 0.47 0.72 0.66 0.11 0.140.57-0.91 0.46-0.88 0.68 0.65 0.95 0.99 0.54 0.33 0.71 0.75 0.10 0.10.58-0.88 0.60-0.94 0.70 0.74 0.93 0.97 0.52 0.56 0.72 0.65 0.11 0.140.59-0.92 0.45-0.86 0.68 0.66 0.96 0.98 0.55 0.32 0.70 0.72 0.09 0.110.58-0.88 0.59-0.92 0.69 0.68 0.91 0.96 0.51 0.55 0.74 0.68 0.13 0.130.52-0.97 0.45-0.85 0.75 0.69 0.97 0.94 0.42 0.44 0.71 0.74 0.11 0.130.55-0.85 0.52-0.97 0.69 0.75 0.98 0.97 0.53 0.423150 0.76 0.75 0.14 0.140.56-0.98 0.52-0.96 0.77 0.76 1.00 0.99 0.49 0.51 0.74 0.76 0.13 0.140.55-0.93 0.56-0.98 0.73 0.77 0.99 1.00 0.53 0.49 0.74 0.72 0.11 0.150.61-0.92 0.51-0.97 0.73 0.70 0.97 0.99 0.54 0.37 0.74 0.77 0.09 0.120.62-0.92 0.62-0.96 0.73 0.76 0.96 0.99 0.59 0.45 0.74 0.71 0.11 0.150.58-0.92 0.51-0.96 0.73 0.69 0.97 0.99 0.57 0.34 0.74 0.74 0.10 0.110.62-0.91 0.58-0.92 0.72 0.73 0.97 0.97 0.62 0.57 0.74 0.73 0.15 0.140.52-0.97 0.52-0.95 0.72 0.74 0.98 0.99 0.39 0.45 0.66 0.74 0.13 0.150.50-0.90 0.52-0.97 0.64 0.72 0.94 0.98 0.43 0.394000 0.72 0.80 0.16 0.120.48-0.95 0.58-0.97 0.73 0.80 0.98 0.99 0.44 0.51 0.66 0.72 0.13 0.160.47-0.87 0.48-0.95 0.65 0.73 0.95 0.98 0.46 0.44 0.70 0.75 0.19 0.180.46-0.94 0.45-0.97 0.72 0.77 0.97 0.98 0.03 0.23 0.68 0.73 0.14 0.150.47-0.90 0.38-0.95 0.68 0.74 0.97 0.97 0.42 0.38 0.69 0.75 0.18 0.180.46-0.94 0.41-0.97 0.70 0.76 0.98 0.98 0.08 0.24 0.69 0.69 0.14 0.180.49-0.90 0.46-0.94 0.67 0.70 0.96 0.98 0.42 0.08 0.68 0.78 0.17 0.120.43-0.95 0.58-0.94 0.63 0.80 0.98 0.97 0.41 0.50 0.58 0.68 0.14 0.170.42-0.83 0.43-0.95 0.55 0.63 0.84 0.98 0.30 0.415000 0.59 0.68 0.16 0.120.35-0.87 0.48-0.85 0.57 0.71 0.97 0.88 0.23 0.47 0.45 0.59 0.10 0.160.32-0.64 0.35-0.87 0.44 0.57 0.75 0.97 0.30 0.23 0.58 0.67 0.23 0.220.12-0.87 0.25-0.94 0.59 0.72 0.99 0.98 0.00 0.00 0.49 0.56 0.20 0.230.01-0.74 0.15-0.87 0.52 0.56 0.82 0.94 0.00 0.00 0.58 0.68 0.23 0.220.13-0.87 0.27-0.95 0.59 0.72 1.00 0.99 0.00 0.00 0.51 0.58 0.21 0.230.05-0.79 0.13-0.87 0.55 0.59 0.96 1.00 -0.03 0.00 0.55 0.65 0.16 0.140.34-0.84 0.39-0.79 0.54 0.69 0.93 0.87 0.31 0.28 0.42 0.55 0.10 0.160.30-0.60 0.34-0.84 0.39 0.54 0.71 0.93 0.26 0.316300 0.45 0.47 0.15 0.120.24-0.71 0.28-0.64 0.42 0.46 0.83 0.69 0.17 0.25 0.33 0.45 0.10 0.150.17-0.49 0.24-0.71 0.34 0.42 0.54 0.83 0.15 0.17 0.47 0.56 0.21 0.20.06-0.80 0.28-0.87 0.46 0.50 0.99 0.95 0.00 0.00 0.35 0.41 0.16 0.220.03-0.57 0.07-0.68 0.36 0.41 0.59 0.97 0.00 0.01 0.39 0.46 0.21 0.190.01-0.69 0.19-0.75 0.38 0.44 0.92 0.87 0 0.00 0.26 0.39 0.14 0.210.05-0.47 0.01-0.69 0.27 0.38 0.52 0.92 -0.09 0.00 0.42 0.44 0.14 0.150.20-0.62 0.15-0.65 0.43 0.45 0.70 0.70 0.01 0.12 0.31 0.42 0.11 0.140.11-0.45 0.20-0.62 0.30 0.43 0.52 0.70 0.03 0.018000 0.45 0.39 0.14 0.160.23-0.66 0.16-0.63 0.41 0.37 0.74 0.88 0.19 0.06 0.35 0.45 0.14 0.140.12-0.54 0.23-0.66 0.35 0.41 0.87 0.74 0.11 0.19 0.29 0.27 0.22 0.180.00-0.64 0.00-0.53 0.27 0.31 0.76 0.57 0 0.00 0.14 0.29 0.15 0.220.00-0.39 0.00-0.64 0.10 0.27 0.58 0.76 0.00 0.00 0.38 0.31 0.18 0.180.08-0.67 0.06-0.59 0.37 0.29 0.75 0.80 0.00 0.06 0.24 0.38 0.16 0.180.00-0.47 0.08-0.67 0.24 0.37 0.64 0.75 0.00 0.00Average	Trials250 0.10 0.07 0.06 0.030.04-0.18 0.02-0.12 0.09 0.06 0.33 0.14 0.03 0.02 0.13 0.10 0.07 0.060.03-0.23 0.04-0.18 0.11 0.09 0.30 0.33 0.01 0.03 0.05 0.04 0.03 0.040.00-0.10 0.00-0.10 0.04 0.03 0.14 0.19 0.00 0.00 0.07 0.04 0.14 0.040.00-0.14 0.00-0.12 0.03 0.02 0.83 0.13 0.00 0.00 0.06 0.05 0.03 0.050.02-0.12 0.00-0.13 0.06 0.04 0.18 0.24 0.01 0.00 0.06 0.06 0.04 0.030.02-0.12 0.02-0.12 0.05 0.06 0.19 0.18 0.01 0.01 0.13 0.08 0.06 0.040.04-0.23 0.02-0.13 0.12 0.09 0.37 0.16 0.03 0.02 0.14 0.13 0.04 0.060.07-0.22 0.04-0.23 0.13 0.12 0.23 0.37 0.06 0.03315 0.10 0.05 0.06 0.030.03-0.19 0.01-0.11 0.09 0.05 0.33 0.13 0.02 0.01 0.13 0.10 0.08 0.060.03-0.25 0.03-0.19 0.11 0.09 0.32 0.33 0.02 0.02 0.08 0.07 0.04 0.050.01-0.14 0.01-0.15 0.08 0.07 0.23 0.23 0.01 0.00 0.10 0.07 0.13 0.050.02-0.21 0.01-0.17 0.07 0.05 0.83 0.19 0.01 0.00 0.09 0.08 0.05 0.060.03-0.16 0.01-0.18 0.09 0.06 0.25 0.25 0.01 0.00 0.09 0.09 0.05 0.050.03-0.16 0.03-0.16 0.08 0.09 0.26 0.25 0.01 0.01 0.13 0.07 0.07 0.040.03-0.25 0.01-0.13 0.12 0.08 0.39 0.17 0.02 0.01 0.15 0.13 0.06 0.070.07-0.25 0.03-0.25 0.14 0.12 0.27 0.39 0.04 0.02400 0.11 0.06 0.07 0.040.03-0.23 0.01-0.14 0.10 0.06 0.35 0.16 0.01 0.00 0.15 0.11 0.09 0.070.01-0.29 0.02-0.23 0.14 0.10 0.34 0.35 0.00 0.01 0.12 0.11 0.06 0.070.04-0.20 0.02-0.24 0.11 0.10 0.35 0.32 0.01 0.01 0.15 0.11 0.13 0.070.04-0.33 0.02-0.26 0.13 0.09 0.83 0.29 0.02 0.01 0.12 0.11 0.06 0.080.04-0.20 0.02-0.24 0.12 0.10 0.36 0.38 0.02 0.01 0.14 0.12 0.07 0.060.04-0.24 0.04-0.20 0.13 0.12 0.36 0.36 0.01 0.02 0.16 0.10 0.09 0.050.04-0.31 0.02-0.18 0.15 0.11 0.42 0.23 0.03 0.01 0.20 0.16 0.07 0.090.09-0.32 0.04-0.31 0.19 0.15 0.35 0.42 0.06 0.03500 0.18 0.13 0.10 0.060.06-0.35 0.04-0.24 0.16 0.12 0.41 0.27 0.04 0.03 0.24 0.18 0.13 0.10.05-0.43 0.05-0.35 0.23 0.16 0.51 0.41 0.02 0.04 0.19 0.17 0.09 0.10.08-0.35 0.04-0.33 0.17 0.16 0.54 0.48 0.04 0.04 0.25 0.18 0.15 0.10.09-0.52 0.06-0.39 0.22 0.17 0.83 0.45 0.02 0.04 0.19 0.17 0.09 0.110.08-0.33 0.04-0.32 0.17 0.15 0.54 0.56 0.04 0.02 0.23 0.19 0.11 0.090.08-0.39 0.08-0.33 0.20 0.17 0.56 0.54 0.03 0.04 0.23 0.16 0.09 0.070.09-0.39 0.05-0.28 0.23 0.17 0.45 0.32 0.07 0.03 0.29 0.23 0.10 0.090.16-0.45 0.09-0.39 0.29 0.23 0.52 0.45 0.11 0.07630 0.25 0.19 0.12 0.090.09-0.48 0.07-0.36 0.24 0.18 0.55 0.41 0.06 0.05 0.35 0.25 0.17 0.120.08-0.63 0.08-0.48 0.34 0.24 0.73 0.55 0.05 0.06 0.28 0.25 0.13 0.130.14-0.47 0.08-0.44 0.25 0.23 0.77 0.75 0.08 0.06 0.37 0.28 0.17 0.130.17-0.70 0.12-0.52 0.35 0.28 0.85 0.59 0.08 0.07 0.29 0.25 0.13 0.150.13-0.51 0.06-0.43 0.26 0.23 0.77 0.88 0.07 0.04 0.36 0.29 0.15 0.130.16-0.63 0.13-0.51 0.33 0.26 0.73 0.77 0.09 0.07 0.32 0.23 0.11 0.10.15-0.49 0.09-0.40 0.31 0.24 0.51 0.44 0.12 0.07 0.41 0.32 0.13 0.110.23-0.61 0.15-0.49 0.41 0.31 0.70 0.51 0.16 0.12800 0.32 0.28 0.17 0.140.10-0.61 0.07-0.51 0.31 0.29 0.78 0.63 0.03 0.04 0.43 0.32 0.19 0.170.11-0.70 0.09-0.61 0.43 0.31 0.74 0.78 0.03 0.03 0.37 0.35 0.15 0.150.20-0.64 0.12-0.56 0.35 0.34 0.93 0.85 0.13 0.09 0.46 0.39 0.18 0.150.22-0.76 0.21-0.66 0.42 0.36 0.88 0.79 0.18 0.12 0.39 0.37 0.15 0.160.20-0.63 0.11-0.59 0.36 0.35 0.95 0.85 0.13 0.08 0.45 0.39 0.16 0.150.22-0.74 0.20-0.63 0.42 0.36 0.79 0.95 0.18 0.13 0.41 0.33 0.14 0.140.19-0.64 0.10-0.54 0.41 0.33 0.71 0.60 0.14 0.07 0.51 0.41 0.14 0.140.29-0.71 0.19-0.64 0.50 0.41 0.77 0.71 0.24 0.141000 0.39 0.38 0.17 0.160.14-0.64 0.10-0.63 0.38 0.39 0.80 0.66 0.03 0.04 0.50 0.39 0.18 0.170.18-0.75 0.13-0.64 0.53 0.38 0.83 0.80 0.07 0.03 0.45 0.45 0.13 0.140.27-0.64 0.21-0.65 0.45 0.46 0.83 0.69 0.21 0.14 0.52 0.51 0.17 0.160.25-0.83 0.30-0.80 0.48 0.49 0.91 0.87 0.21 0.21 0.47 0.46 0.13 0.150.28-0.64 0.20-0.68 0.46 0.45 0.84 0.76 0.22 0.14 0.52 0.47 0.16 0.130.26-0.79 0.28-0.64 0.50 0.46 0.85 0.84 0.22 0.22 0.51 0.43 0.15 0.160.24-0.72 0.14-0.70 0.52 0.45 0.78 0.72 0.21 0.12 0.59 0.51 0.12 0.150.36-0.77 0.24-0.72 0.60 0.52 0.81 0.78 0.32 0.211250 0.48 0.46 0.15 0.130.24-0.70 0.22-0.66 0.48 0.47 0.75 0.72 0.11 0.16 0.55 0.48 0.14 0.150.31-0.78 0.25-0.70 0.56 0.48 0.84 0.75 0.20 0.11 0.51 0.49 0.11 0.130.31-0.69 0.30-0.71 0.52 0.49 0.72 0.74 0.30 0.27 0.55 0.58 0.16 0.130.32-0.83 0.36-0.78 0.53 0.57 0.93 0.84 0.26 0.29 0.52 0.50 0.11 0.120.34-0.69 0.31-0.71 0.51 0.50 0.78 0.75 0.31 0.28 0.56 0.52 0.15 0.110.32-0.81 0.34-0.69 0.54 0.51 0.91 0.78 0.26 0.31 0.59 0.52 0.12 0.130.39-0.76 0.28-0.72 0.59 0.54 0.82 0.74 0.35 0.27 0.63 0.59 0.09 0.120.50-0.78 0.39-0.76 0.62 0.59 0.84 0.82 0.42 0.351600 0.54 0.51 0.13 0.150.34-0.73 0.27-0.75 0.55 0.50 0.81 0.83 0.31 0.22 0.58 0.54 0.13 0.130.38-0.77 0.34-0.73 0.58 0.55 0.80 0.81 0.27 0.31 0.56 0.53 0.11 0.150.36-0.70 0.30-0.74 0.58 0.54 0.74 0.78 0.31 0.14 0.59 0.59 0.13 0.130.38-0.74 0.41-0.81 0.60 0.58 0.91 0.88 0.28 0.30 0.58 0.54 0.11 0.150.38-0.73 0.30-0.75 0.59 0.55 0.78 0.80 0.30 0.14 0.59 0.58 0.12 0.110.37-0.73 0.38-0.73 0.61 0.59 0.86 0.78 0.29 0.30 0.62 0.56 0.09 0.140.43-0.74 0.31-0.75 0.63 0.57 0.77 0.77 0.40 0.26 0.64 0.62 0.09 0.090.52-0.75 0.43-0.74 0.64 0.63 0.85 0.77 0.48 0.402000 0.60 0.53 0.13 0.140.35-0.77 0.27-0.73 0.60 0.54 0.85 0.78 0.33 0.20 0.61 0.60 0.13 0.130.43-0.81 0.36-0.77 0.62 0.60 0.90 0.85 0.33 0.33 0.64 0.59 0.12 0.150.44-0.81 0.36-0.77 0.63 0.61 0.94 0.85 0.40 0.17 0.64 0.65 0.10 0.120.48-0.79 0.50-0.88 0.65 0.63 0.87 0.92 0.37 0.46 0.65 0.59 0.12 0.150.45-0.89 0.35-0.77 0.63 0.62 0.98 0.86 0.41 0.16 0.63 0.65 0.10 0.120.46-0.77 0.45-0.89 0.64 0.63 0.87 0.98 0.37 0.41 0.66 0.58 0.11 0.140.43-0.81 0.34-0.76 0.66 0.61 0.88 0.79 0.39 0.30 0.64 0.66 0.10 0.110.49-0.80 0.43-0.81 0.63 0.66 0.94 0.88 0.43 0.392500 0.73 0.66 0.14 0.130.50-0.95 0.47-0.87 0.75 0.67 0.97 0.91 0.46 0.40 0.71 0.73 0.12 0.140.54-0.89 0.48-0.95 0.70 0.75 0.96 0.97 0.50 0.46 0.71 0.65 0.12 0.140.56-0.92 0.46-0.86 0.69 0.64 0.97 0.96 0.48 0.33 0.70 0.75 0.09 0.10.57-0.85 0.61-0.93 0.71 0.73 0.90 0.98 0.50 0.57 0.72 0.64 0.12 0.140.58-0.91 0.45-0.87 0.69 0.64 0.98 0.96 0.54 0.32 0.69 0.72 0.09 0.120.55-0.85 0.58-0.91 0.70 0.69 0.88 0.98 0.49 0.54 0.75 0.67 0.13 0.130.52-0.97 0.47-0.85 0.76 0.69 0.97 0.93 0.44 0.44 0.71 0.75 0.10 0.130.56-0.86 0.52-0.97 0.70 0.76 0.96 0.97 0.54 0.443150 0.77 0.75 0.15 0.130.56-0.97 0.54-0.96 0.79 0.77 0.99 0.98 0.47 0.49 0.74 0.77 0.12 0.150.56-0.93 0.52-0.97 0.73 0.79 0.98 0.99 0.52 0.47 0.74 0.71 0.11 0.140.60-0.91 0.50-0.95 0.73 0.70 0.97 0.97 0.54 0.38 0.73 0.77 0.10 0.110.60-0.90 0.62-0.94 0.72 0.76 0.94 0.99 0.54 0.51 0.74 0.70 0.11 0.150.59-0.92 0.49-0.95 0.73 0.69 0.97 0.98 0.57 0.34 0.73 0.74 0.11 0.110.60-0.90 0.59-0.92 0.72 0.73 0.94 0.97 0.43 0.57 0.74 0.73 0.16 0.140.52-0.96 0.51-0.95 0.73 0.74 0.98 0.98 0.40 0.43 0.66 0.74 0.12 0.160.48-0.87 0.52-0.96 0.64 0.73 0.91 0.98 0.38 0.404000 0.72 0.81 0.16 0.120.48-0.94 0.61-0.96 0.74 0.80 0.98 0.98 0.44 0.49 0.66 0.72 0.13 0.160.46-0.86 0.48-0.94 0.65 0.74 0.91 0.98 0.40 0.44 0.71 0.75 0.17 0.180.48-0.93 0.42-0.96 0.72 0.77 0.97 0.97 0.16 0.22 0.67 0.72 0.15 0.140.47-0.89 0.44-0.92 0.66 0.74 0.96 0.96 0.37 0.39 0.70 0.74 0.17 0.180.48-0.94 0.40-0.96 0.70 0.76 0.98 0.98 0.16 0.23 0.68 0.70 0.15 0.170.48-0.90 0.48-0.94 0.67 0.70 0.96 0.98 0.21 0.16 0.67 0.78 0.18 0.120.42-0.94 0.58-0.95 0.64 0.78 0.98 0.97 0.39 0.47 0.57 0.67 0.15 0.180.40-0.81 0.42-0.94 0.54 0.64 0.84 0.98 0.15 0.395000 0.58 0.69 0.15 0.120.35-0.83 0.48-0.86 0.56 0.70 0.97 0.90 0.27 0.43 0.45 0.58 0.11 0.150.32-0.65 0.36-0.83 0.44 0.56 0.73 0.97 0.26 0.27 0.58 0.68 0.22 0.210.13-0.87 0.29-0.94 0.59 0.72 0.99 0.98 0.02 0.04 0.50 0.55 0.19 0.230.12-0.75 0.14-0.85 0.53 0.56 0.80 0.94 0.05 0.00 0.58 0.68 0.22 0.210.18-0.87 0.32-0.95 0.60 0.72 0.99 0.98 0.00 0.08 0.51 0.58 0.20 0.220.14-0.78 0.18-0.87 0.56 0.60 0.95 0.99 -0.01 0.00 0.54 0.64 0.16 0.140.34-0.84 0.38-0.81 0.53 0.69 0.93 0.86 0.29 0.28 0.41 0.54 0.11 0.160.28-0.60 0.34-0.84 0.39 0.53 0.72 0.93 0.13 0.296300 0.44 0.46 0.14 0.120.24-0.64 0.27-0.64 0.42 0.45 0.76 0.71 0.16 0.24 0.34 0.44 0.11 0.140.15-0.49 0.23-0.64 0.35 0.42 0.59 0.76 0.12 0.16 0.47 0.57 0.21 0.190.08-0.77 0.30-0.84 0.47 0.56 0.99 0.96 0.00 0.11 0.36 0.40 0.17 0.220.08-0.64 0.04-0.68 0.36 0.43 0.70 0.95 0.05 0.01 0.39 0.47 0.20 0.180.04-0.67 0.22-0.73 0.39 0.44 0.91 0.88 0.00 0.05 0.27 0.39 0.14 0.20.08-0.49 0.04-0.67 0.26 0.39 0.56 0.91 -0.02 0.00 0.41 0.44 0.15 0.150.18-0.63 0.16-0.64 0.41 0.45 0.69 0.71 0.01 0.12 0.30 0.41 0.11 0.150.11-0.43 0.18-0.63 0.30 0.41 0.54 0.69 0.02 0.018000 0.45 0.40 0.15 0.160.23-0.71 0.19-0.70 0.41 0.36 0.82 0.85 0.18 0.09 0.36 0.45 0.14 0.150.11-0.56 0.23-0.71 0.36 0.41 0.79 0.82 0.09 0.18 0.28 0.27 0.21 0.180.00-0.64 0.00-0.52 0.26 0.32 0.71 0.60 0.00 0.00 0.14 0.28 0.14 0.210.00-0.37 0.00-0.64 0.10 0.26 0.57 0.71 0.00 0.00 0.36 0.31 0.18 0.170.08-0.66 0.06-0.59 0.33 0.29 0.77 0.80 0.00 0.05 0.23 0.36 0.16 0.180.00-0.47 0.08-0.66 0.22 0.33 0.58 0.77 0.00 0.00Max	upper	range	MedianTitan	Interacoustics	SystemChinese	Group	 Caucasian	GroupMean Standard	Deviation 5th	-	95th	Percentile Median Max	upper	range	 Min	lower	range	 Min	lower	range	Mean Standard	Deviation 5th	-	95th	Percentile MedianMin	lower	range	 Mean 5th	-	95th	Percentile 5th	-	95th	Percentile Median Median Max	upper	range	 Min	lower	range	5th	-	95th	PercentileMin	lower	range	 Max	upper	range	 Min	lower	range	 Mean Standard	DeviationMean Standard	Deviation 5th	-	95th	Percentile Median Max	upper	range	HearID	Mimosa	Acoustics	SystemCaucasian	GroupOtostat	Mimosa	Acoustics	SystemChinese	Group	 Caucasian	GroupChinese	Group	Standard	Deviation Mean Standard	DeviationMedian Max	upper	range	RefWin	Interacoustics	SystemMean Standard	Deviation 5th	-	95th	Percentile MeanMedian Max	upper	range	 Min	lower	range	Chinese	Group	 Caucasian	GroupStandard	Deviation 5th	-	95th	Percentile Max	upper	range	 Min	lower	range	 ..\..\Descriptive Statistics\table 1_OVERALL PA summary.xlsx    A.3 Descriptive Statistics for Other Variables  Descriptive statistics including mean, median, standard deviation, 5th – 95th percentile, maximum, and minimum for parameters of RF, Ytm, TPP, RAI, and ECV.  187   A.4 Descriptive Statistics for Admittance Magnitude Descriptive statistics including mean, median, standard deviation, 5th – 95th percentile, maximum, and minimum for admittance magnitude (Y) measured across 250 – 8000 Hz using the ReflWin system in trial 1 and trial 2.  RAIMale Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male FemaleTrial	1 59.52 56.83 58.77 58.79 49.46 44.70 43.80 43.83 69.18 66.63 71.15 76.45 74.79 71.61 73.21 87.06 42.14 42.51 42.12 42.39 6.86 6.30 7.96 10.43 60.03 58.21 59.57 57.86Trial	2 58.65 55.83 58.03 58.39 44.63 45.17 43.47 43.97 69.55 66.78 71.51 74.69 71.01 70.84 74.16 87.17 43.67 44.03 40.17 40.56 7.51 7.08 8.51 10.50 59.67 55.73 58.22 57.37Avg		of	Trials 59.09 56.33 58.40 58.59 47.04 44.94 43.63 43.90 69.36 66.70 71.33 75.57 72.90 71.22 73.68 87.12 42.90 43.27 41.14 41.47 7.18 6.69 8.24 10.47 59.85 56.97 58.89 57.61YtmMale Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male FemaleTrial	1 0.68 0.40 0.45 0.37 0.40 0.20 0.20 0.20 1.14 1.28 0.72 0.60 1.20 1.50 0.80 0.80 0.30 0.20 0.20 0.20 0.23 1.47 0.16 0.14 0.65 0.50 0.40 0.40Trial	2 0.70 0.62 0.43 0.39 0.40 0.30 0.20 0.20 1.20 1.37 0.70 0.62 1.40 1.60 0.90 0.72 0.30 0.20 0.20 0.20 0.25 0.33 0.17 0.15 0.70 0.50 0.40 0.40Avg		of	Trials 0.69 0.51 0.44 0.38 0.40 0.25 0.20 0.20 1.17 1.33 0.71 0.61 1.30 1.55 0.85 0.76 0.30 0.20 0.20 0.20 0.24 0.90 0.16 0.15 0.68 0.50 0.40 0.40TPPMale Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male FemaleTrial	1 -9.68 -4.43 -9.76 -10.08 -27.45 -22.10 -23.60 -23.15 2.30 7.40 0.00 0.60 8.00 78.00 1.00 12.00 -65.00 -25.00 -29.00 -58.00 13.17 15.12 7.89 10.95 -7.00 -5.00 -9.00 -9.00Trial	2 -11.63 -3.09 -12.05 -11.97 -25.00 -17.00 -32.00 -26.30 3.30 10.20 -0.85 4.60 13.00 80.00 3.00 17.00 -74.00 -28.00 -40.00 -43.00 13.87 17.46 10.70 11.11 -11.00 -4.00 -9.00 -13.00Avg		of	Trials -10.65 -3.76 -10.91 -11.03 -26.23 -19.55 -27.80 -24.73 2.80 8.80 -0.43 2.60 10.50 79.00 2.00 14.50 -69.50 -26.50 -34.50 -50.50 13.52 16.29 9.30 11.03 -9.00 -4.50 -9.00 -11.00RFMale Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male FemaleTrial	1 974.05 939.00 1309.13 1394.50 627.15 503.30 706.95 863.35 1541.10 1356.85 2443.20 4319.25 2448.00 1563.00 4559.00 5096.00 572.00 250.00 459.00 763.00 347.76 262.21 777.34 1011.31 877.50 947.50 1043.00 1044.50Trial	2 975.13 928.85 1257.82 1286.68 638.70 629.75 661.00 864.10 1514.45 1308.25 2398.70 2547.75 3451.00 1543.00 3554.00 4775.00 508.00 359.00 323.00 791.00 463.03 236.55 629.78 771.92 875.50 907.50 1053.00 1039.50Avg		of	Trials 974.59 933.92 1292.03 1340.59 632.93 566.53 691.63 863.73 1527.78 1332.55 2428.37 3433.50 2949.50 1553.00 4224.00 4935.50 540.00 304.50 413.67 777.00 405.39 249.38 728.15 891.62 876.50 927.50 1046.33 1042.00ECVMale Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male FemaleRefWin	Trial	1 1.58 1.26 1.31 1.03 1.11 0.80 0.84 0.76 2.30 1.91 1.85 1.46 3.41 2.32 1.93 1.60 1.00 0.70 0.71 0.75 0.22 0.32 0.36 0.48 1.48 1.20 1.34 1.03RefWin	Trial	2 1.52 1.20 1.24 1.04 1.09 0.77 0.79 0.74 2.19 1.83 1.70 1.53 3.33 2.21 1.83 1.75 0.98 0.66 0.70 0.66 0.26 0.29 0.35 0.46 1.42 1.18 1.28 1.02HearID	Trial	1 1.04 0.90 1.01 0.79 0.81 0.51 0.64 0.62 1.35 1.23 1.41 1.00 1.50 1.48 1.55 1.28 0.78 0.42 0.61 0.50 0.14 0.26 0.22 0.18 1.03 0.90 0.94 0.78HearID	Trial	2 1.09 0.90 1.01 0.79 0.82 0.55 0.66 0.55 1.37 1.39 1.44 1.00 1.75 1.56 1.60 1.36 0.77 0.43 0.62 0.50 0.15 0.24 0.25 0.20 1.06 0.90 0.99 0.77Otostat	Trial	1 1.27 1.10 1.12 0.95 0.94 0.70 0.82 0.70 1.73 1.73 1.43 1.25 2.10 2.03 2.19 1.36 0.84 0.63 0.70 0.62 0.19 0.25 0.34 0.29 1.22 1.02 1.09 0.93Otostat	Trial	2 1.30 1.06 1.12 0.97 0.92 0.73 0.83 0.66 1.91 1.59 1.46 1.33 2.09 1.67 1.88 1.50 0.82 0.67 0.73 0.63 0.22 0.22 0.28 0.31 1.29 0.94 1.10 0.96Titan	Trial	1 1.31 1.09 1.13 1.01 0.92 0.73 0.82 0.66 2.02 1.74 1.47 1.30 2.06 2.09 2.11 3.51 0.84 0.64 0.66 0.62 0.46 0.25 0.34 0.31 1.22 1.01 1.12 0.94Titan	Trial	2 1.32 1.07 1.15 0.98 0.91 0.72 0.85 0.64 1.93 1.70 1.49 1.36 2.35 1.75 1.99 1.71 0.86 0.69 0.67 0.61 0.25 0.24 0.31 0.36 1.27 0.96 1.13 0.94Avg		of	Trials 1.30 1.07 1.13 0.95 0.94 0.69 0.78 0.66 1.85 1.64 1.53 1.28 2.32 1.89 1.88 1.76 0.86 0.60 0.68 0.61 0.24 0.26 0.31 0.32 1.25 1.01 1.12 0.92Caucasian Chinese Caucasian ChineseChineseCaucasian Chinese Caucasian Chinese CaucasianCaucasian Chinese Caucasian ChineseMean 5th	Percentile 95th	Percentile Max	Upper	Range Min	Lower	RangeCaucasian Chinese Caucasian Chinese Caucasian ChineseCaucasian Chinese Caucasian ChineseMean 5th	Percentile 95th	Percentile Max	Upper	Range Min	Lower	RangeCaucasian Chinese Caucasian Chinese Caucasian ChineseCaucasian Chinese Caucasian ChineseMean 5th	Percentile 95th	Percentile Max	Upper	Range Min	Lower	RangeCaucasian Chinese Caucasian Chinese Caucasian ChineseCaucasian Chinese Caucasian ChineseStandard	DeviationMin	Lower	RangeCaucasian ChineseMean 5th	Percentile 95th	Percentile Max	Upper	Range Min	Lower	RangeCaucasian ChineseMean 5th	Percentile 95th	Percentile Max	Upper	RangeCaucasian ChineseStandard	DeviationCaucasian ChineseStandard	DeviationCaucasian ChineseMedianCaucasian Chinese Caucasian ChineseMedianCaucasian ChineseStandard	DeviationCaucasian ChineseStandard	DeviationCaucasian ChineseMedianCaucasian ChineseMedianCaucasian ChineseMedianCaucasian Chinese188   Admittance	MagnitudeFrequency	(Hz)Trial	1 Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female Male Female250 3.40 1.35 2.23 1.84 -0.20-6.80 -1.18-4.65 3.80 1.65 7.56 5.33 -1.71 -1.32 4.80 2.91 2.37 2.48 2.10-8.55 -0.82-7.17 4.52 2.90 12.33 8.82 0.00 -1.88315 4.29 2.31 2.15 1.85 0.58-7.60 -0.30-5.33 4.71 2.62 8.00 6.75 -0.53 -0.37 5.77 3.79 2.35 2.46 2.83-9.54 0.24-8.06 5.64 3.77 13.48 9.66 0.69 -0.99397 6.79 4.95 1.97 1.68 3.37-9.25 2.54-7.80 7.27 5.03 10.63 8.55 2.47 2.28 8.26 6.32 2.28 2.39 5.49-12.053.03-10.63 8.08 6.26 15.62 12.34 3.33 1.87500 9.07 7.35 1.89 1.67 5.79-11.39 4.88-10.05 9.65 7.48 13.36 11.03 5.03 4.49 10.58 8.63 2.26 2.46 7.85-14.355.35-13.08 10.43 8.34 17.88 14.92 5.71 4.41630 11.05 9.40 1.96 1.73 7.58-13.78 6.55-11.97 11.34 9.68 16.19 13.21 6.93 5.76 12.48 10.58 2.21 2.57 9.80-16.447.33-15.14 12.22 10.13 19.06 16.61 7.96 5.33794 12.66 11.24 2.10 1.84 9.02-15.46 8.05-13.76 12.70 11.59 19.25 15.63 8.49 7.67 13.88 11.96 2.01 2.43 11.02-17.568.97-16.13 13.71 11.57 19.55 18.22 9.87 7.321000 14.04 12.88 1.89 1.58 10.83-16.61 10.36-15.33 13.96 12.89 17.77 16.09 9.80 10.01 15.10 13.19 1.88 1.90 12.71-19.1310.68-16.65 14.87 12.88 21.04 19.06 12.30 10.041260 15.95 14.72 1.92 1.49 13.16-18.76 12.66-18.09 16.21 14.58 19.45 18.35 11.98 12.23 16.93 14.82 1.72 1.58 15.05-19.3612.52-17.18 16.77 14.68 23.26 19.06 13.21 12.141587 17.65 16.44 2.18 1.64 13.79-20.56 14.19-19.87 17.78 16.18 22.73 20.12 11.66 13.30 18.93 16.25 1.65 2.02 16.27-21.4213.22-19.49 18.93 16.08 22.35 20.56 15.38 12.712000 20.59 18.32 2.54 1.99 16.61-24.22 14.98-20.92 20.52 18.46 27.87 23.54 15.30 13.71 21.62 19.12 1.63 2.43 19.11-24.1014.58-22.91 21.51 19.18 25.58 23.66 18.61 13.662520 23.67 21.58 2.87 2.33 19.30-27.70 18.37-24.83 23.35 21.59 31.37 27.87 17.87 16.60 25.11 22.19 2.27 3.65 21.57-28.9617.95-28.45 24.98 22.31 29.13 29.60 21.27 11.463175 26.55 25.50 3.31 2.63 21.20-31.66 21.72-29.79 26.32 25.61 32.62 31.75 19.35 20.90 28.67 25.33 3.01 4.62 23.84-33.6516.11-30.99 28.69 25.67 34.51 33.92 22.72 10.434000 26.96 26.93 5.18 3.71 18.98-35.96 19.32-32.39 26.14 26.97 36.05 35.07 15.46 16.80 29.56 26.07 3.47 4.42 23.32-34.7417.87-30.49 29.46 27.37 39.22 31.59 22.21 8.475040 22.96 25.00 6.34 5.04 11.23-31.50 17.75-31.04 23.75 25.39 35.44 31.55 9.06 10.12 24.64 22.47 4.73 6.55 19.18-33.111.11-30.06 23.71 23.29 35.69 33.88 16.18 -0.896350 16.63 18.20 5.28 5.44 7.67-24.20 9.47-26.14 16.73 19.01 27.09 26.35 7.08 3.02 16.75 16.16 4.13 6.60 11.08-23.794.10-22.78 15.89 17.47 25.46 34.50 10.07 -1.758000 13.37 13.63 5.43 3.90 5.14-21.66 4.43-18.47 12.58 14.35 32.70 19.46 4.37 3.69 11.24 11.57 4.97 5.47 5.10-19.283.04-23.62 10.23 11.21 21.06 26.76 0.87 0.24Trial	2250 3.89 1.36 2.41 2.14 -0.45-7.42 -1.40-4.96 4.69 1.48 8.18 6.17 -1.26 -2.26 4.70 2.99 2.13 2.68 1.84-7.97 -0.76-7.69 4.55 2.79 8.15 9.05 0.55 -3.72315 4.76 2.32 2.28 2.11 0.90-8.12 -0.50-6.06 5.37 2.36 8.91 6.78 -0.12 -1.22 5.69 3.89 2.10 2.64 2.93-8.92 0.43-8.71 5.56 3.75 9.15 9.89 1.26 -2.74397 7.19 4.96 2.06 1.96 3.75-10.31 2.33-8.17 7.88 4.86 10.91 9.24 2.84 1.49 8.22 6.45 2.07 2.55 5.43-11.413.39-11.28 8.10 6.23 11.89 12.58 3.98 0.21500 9.40 7.37 1.89 1.91 6.22-11.95 4.75-10.57 9.97 7.26 12.70 11.44 5.31 3.94 10.56 8.77 2.08 2.56 7.86-13.715.54-13.62 10.40 8.50 14.67 15.10 6.36 2.80630 11.28 9.45 1.77 1.92 8.40-13.50 6.85-12.75 11.64 9.46 14.60 13.26 7.20 5.55 12.42 10.72 1.99 2.61 10.01-15.627.25-15.41 12.04 10.52 17.14 16.68 8.62 4.99794 12.81 11.26 1.66 2.00 9.77-15.06 8.29-14.40 12.98 10.89 15.84 14.85 8.77 6.96 13.61 12.19 1.48 2.49 11.62-15.88.82-16.62 13.60 11.91 17.81 18.53 10.74 6.921000 14.10 12.65 1.90 1.70 11.13-16.62 10.22-15.54 14.02 12.33 17.71 16.13 8.95 9.47 14.71 13.25 1.31 1.69 13.03-17.4610.14-16.03 14.43 13.32 17.82 16.77 12.73 9.431260 16.17 14.38 2.34 1.47 12.82-19.38 12.32-17.05 16.29 14.17 20.79 17.49 10.32 12.27 16.67 14.74 1.46 1.73 14.59-19.1211.94-17.67 16.73 14.59 19.77 18.42 12.74 11.281587 17.76 15.71 2.29 1.58 14.63-21.46 13.33-17.94 17.27 15.68 23.35 18.95 13.01 11.04 18.52 16.13 1.68 2.20 15.25-20.8412.91-19.33 18.67 16.51 22.23 21.35 14.77 11.852000 20.37 17.57 2.70 2.59 16.63-23.80 14.13-20.51 20.67 18.12 27.25 21.80 15.38 9.23 21.33 19.12 1.80 2.50 18.83-24.3515.77-23.39 21.72 19.16 25.12 24.74 17.29 13.302520 23.73 20.89 3.52 2.85 18.73-30.19 16.65-24.29 23.54 21.32 32.98 27.34 17.99 13.14 24.96 22.22 2.31 3.32 21.66-28.7217.79-28.76 25.04 22.29 29.64 31.11 21.12 14.893175 26.93 24.90 3.83 2.92 21.31-32.47 20.42-29.14 26.78 24.90 35.12 31.27 19.74 18.56 28.42 25.39 3.20 3.43 23.97-33.3821.06-29.75 28.04 26.01 33.96 32.96 20.69 11.574000 27.15 26.26 5.21 3.84 18.82-33.81 19.01-31.37 27.27 26.41 34.54 34.33 15.41 16.72 29.56 26.78 3.82 4.65 23.84-35.321.22-32.43 30.53 27.47 35.65 35.59 21.40 9.195040 22.46 24.90 5.66 5.75 11.76-30.55 14.90-31.84 23.01 24.83 32.53 33.04 8.65 10.23 24.55 24.00 4.91 6.70 17.79-32.9216.23-33.32 24.08 24.13 36.72 38.25 15.29 0.636350 16.80 18.32 4.91 6.18 8.61-22.71 9.53-25.21 17.25 18.34 28.29 30.16 6.60 3.13 16.82 17.37 4.16 5.70 10.64-24.159.29-27.09 16.42 17.28 25.99 30.93 9.32 3.418000 14.17 13.88 7.16 4.29 6.96-31.61 5.24-19.71 12.42 14.31 33.55 22.44 1.58 3.56 11.18 11.81 5.27 5.29 4.85-19.114.87-22.12 10.11 11.68 24.50 24.81 3.12 -2.43Min	lower	range	Max	upper	range	Median5th	-	95th	PercentileStandard	DeviationMean 5th	-	95th	Percentile Median Max	upper	range	 Min	lower	range	Standard	DeviationMeanChinese	Group	 Caucasian	Group189  A.5  Descriptive Statistics for Power Absorbance by System at Ambient Pressure  Mean, median, standard deviation, 5th – 95th percentile, maximum, and minimum power absorbance values listed across frequencies and grouped by trials and system at ambient pressure conditions.  Current	Study:	Ambient	PressureRefWin HearID Otostat TitanFrequency	(Hz)Mean 5th	Percentile95th	PercentileS andard	DeviationMedian Max	Upper	Range	(Largest	Value)Mi 	Lower	Range	(Lowest	Value)Mean 5th	Percentile95th	PercentileStandard	DeviationMedian Max	Upper	Range	(Largest	Value)Min	Lower	Range	(Lowest	Value)M an 5th	Percentile95th	PercentileStandard	DeviationMedian Max	Upper	Range	(Largest	Value)Min	Lower	Range	(Lowest	Value)M an 5th	Percentile95th	PercentileStandard	DeviationMedian Max	Upper	Range	(Largest	Value)Min	Lower	Range	(Lowest	Value)Run	1250 0.09 0.03 0.22 0.06 0.08 0.35 0.01 0.05 0.00 0.13 0.08 0.03 0.84 0.00 0.05 0.01 0.12 0.04 0.05 0.27 0.00 0.12 0.04 0.22 0.06 0.11 0.40 0.01315 0.09 0.02 0.22 0.06 0.08 0.38 0.00 0.08 0.01 0.17 0.08 0.06 0.83 0.00 0.08 0.02 0.17 0.05 0.07 0.27 0.00 0.12 0.02 0.24 0.07 0.11 0.42 0.01400 0.10 0.01 0.28 0.08 0.08 0.39 0.00 0.12 0.02 0.26 0.09 0.11 0.82 0.01 0.12 0.03 0.26 0.07 0.11 0.39 0.01 0.16 0.03 0.32 0.09 0.15 0.44 0.01500 0.18 0.04 0.41 0.11 0.15 0.54 0.00 0.20 0.05 0.41 0.12 0.18 0.83 0.01 0.19 0.06 0.39 0.10 0.17 0.57 0.01 0.24 0.07 0.46 0.11 0.22 0.57 0.03630 0.26 0.07 0.55 0.15 0.23 0.74 0.01 0.29 0.11 0.57 0.15 0.26 0.86 0.06 0.29 0.10 0.55 0.14 0.27 0.91 0.06 0.33 0.11 0.58 0.15 0.32 0.78 0.07800 0.34 0.08 0.69 0.18 0.31 0.83 0.02 0.39 0.17 0.72 0.16 0.36 0.94 0.09 0.40 0.17 0.69 0.16 0.38 0.95 0.09 0.43 0.15 0.70 0.17 0.43 0.88 0.081000 0.42 0.13 0.78 0.19 0.40 0.94 0.00 0.48 0.22 0.78 0.16 0.46 0.94 0.14 0.49 0.23 0.75 0.15 0.47 0.93 0.14 0.52 0.24 0.77 0.16 0.53 0.84 0.131250 0.50 0.26 0.72 0.14 0.50 0.86 0.05 0.53 0.29 0.75 0.14 0.53 0.92 0.21 0.54 0.32 0.76 0.13 0.53 0.88 0.20 0.60 0.38 0.76 0.12 0.60 0.85 0.271600 0.54 0.33 0.76 0.14 0.54 0.85 0.20 0.56 0.33 0.74 0.14 0.57 0.90 0.13 0.57 0.33 0.75 0.13 0.58 0.92 0.13 0.61 0.40 0.75 0.11 0.62 0.92 0.272000 0.59 0.37 0.81 0.13 0.60 0.87 0.21 0.62 0.42 0.81 0.13 0.64 0.93 0.16 0.63 0.42 0.84 0.13 0.63 0.98 0.16 0.63 0.40 0.82 0.12 0.63 0.98 0.292500 0.71 0.49 0.91 0.13 0.72 0.99 0.42 0.70 0.49 0.89 0.12 0.69 0.99 0.32 0.69 0.51 0.89 0.12 0.69 1.00 0.31 0.72 0.52 0.93 0.12 0.73 0.97 0.433150 0.76 0.55 0.96 0.13 0.78 0.99 0.46 0.74 0.58 0.92 0.11 0.74 0.99 0.38 0.73 0.57 0.93 0.12 0.73 1.00 0.24 0.71 0.49 0.94 0.14 0.72 0.98 0.324000 0.74 0.48 0.95 0.14 0.75 0.99 0.35 0.71 0.47 0.93 0.15 0.73 0.98 0.22 0.71 0.48 0.94 0.16 0.71 0.98 0.00 0.67 0.42 0.95 0.17 0.68 0.98 0.005000 0.56 0.32 0.85 0.16 0.54 0.97 0.19 0.57 0.13 0.89 0.22 0.60 0.99 0.00 0.58 0.18 0.93 0.22 0.59 0.99 0.00 0.51 0.27 0.78 0.17 0.48 0.93 0.006300 0.38 0.16 0.62 0.14 0.39 0.77 0.05 0.46 0.10 0.77 0.21 0.47 0.98 0.00 0.36 0.05 0.69 0.19 0.37 0.90 0.00 0.36 0.11 0.63 0.15 0.36 0.72 0.008000 0.36 0.12 0.66 0.16 0.34 0.89 0.03 0.21 0.00 0.57 0.18 0.20 0.67 0.00 0.27 0.00 0.59 0.18 0.26 0.79 0.00Run	2250 0.10 0.03 0.22 0.06 0.09 0.34 0.01 0.05 0.00 0.11 0.07 0.04 0.83 0.00 0.06 0.00 0.13 0.04 0.05 0.21 -0.01 0.12 0.03 0.23 0.06 0.11 0.35 0.02315 0.09 0.02 0.23 0.06 0.08 0.33 0.00 0.08 0.01 0.17 0.08 0.07 0.83 0.00 0.08 0.02 0.18 0.05 0.08 0.27 -0.01 0.12 0.02 0.26 0.07 0.11 0.35 0.01400 0.11 0.01 0.27 0.08 0.09 0.36 0.00 0.12 0.03 0.27 0.09 0.11 0.83 0.01 0.12 0.02 0.26 0.07 0.11 0.40 0.00 0.16 0.04 0.35 0.09 0.14 0.39 0.01500 0.19 0.05 0.40 0.11 0.16 0.51 0.01 0.20 0.06 0.38 0.11 0.17 0.83 0.03 0.20 0.06 0.39 0.10 0.18 0.59 0.00 0.24 0.08 0.45 0.11 0.22 0.56 0.04630 0.28 0.07 0.55 0.15 0.26 0.72 0.02 0.30 0.11 0.55 0.14 0.26 0.84 0.06 0.30 0.10 0.54 0.14 0.28 0.85 0.03 0.33 0.12 0.60 0.14 0.31 0.75 0.06800 0.36 0.08 0.71 0.19 0.35 0.86 0.00 0.40 0.20 0.68 0.16 0.36 0.92 0.08 0.41 0.19 0.67 0.16 0.39 0.94 0.08 0.43 0.15 0.70 0.17 0.42 0.87 0.061000 0.44 0.14 0.69 0.18 0.44 0.88 0.01 0.49 0.26 0.81 0.15 0.47 0.88 0.13 0.50 0.27 0.82 0.15 0.49 0.89 0.13 0.52 0.22 0.78 0.16 0.52 0.88 0.121250 0.51 0.24 0.74 0.14 0.53 0.88 0.12 0.54 0.32 0.75 0.13 0.53 0.95 0.27 0.55 0.33 0.76 0.13 0.53 0.95 0.27 0.59 0.35 0.77 0.12 0.60 0.83 0.231600 0.54 0.32 0.76 0.14 0.55 0.86 0.20 0.58 0.36 0.78 0.13 0.58 0.97 0.15 0.59 0.36 0.79 0.13 0.60 0.97 0.15 0.60 0.40 0.75 0.11 0.61 0.82 0.252000 0.57 0.35 0.78 0.14 0.58 0.94 0.19 0.64 0.45 0.85 0.12 0.63 0.95 0.17 0.64 0.44 0.87 0.12 0.63 0.97 0.16 0.62 0.41 0.78 0.12 0.63 0.90 0.302500 0.70 0.50 0.92 0.13 0.70 0.99 0.37 0.71 0.53 0.92 0.12 0.70 0.99 0.33 0.71 0.52 0.92 0.12 0.70 0.98 0.32 0.72 0.51 0.93 0.12 0.72 0.98 0.413150 0.76 0.55 0.96 0.13 0.76 1.00 0.49 0.74 0.55 0.96 0.12 0.73 0.99 0.37 0.74 0.57 0.95 0.12 0.73 0.99 0.34 0.72 0.50 0.94 0.14 0.71 0.99 0.324000 0.73 0.48 0.96 0.15 0.74 0.99 0.44 0.72 0.45 0.96 0.17 0.74 0.98 0.03 0.72 0.42 0.96 0.16 0.73 0.98 0.08 0.68 0.43 0.95 0.17 0.68 0.98 0.305000 0.57 0.32 0.84 0.16 0.56 0.97 0.18 0.58 0.09 0.89 0.22 0.59 0.99 0.00 0.58 0.13 0.92 0.23 0.59 1.00 -0.03 0.53 0.29 0.80 0.17 0.53 0.94 0.216300 0.39 0.17 0.63 0.15 0.38 0.83 0.00 0.45 0.06 0.78 0.21 0.44 0.99 0.00 0.35 0.03 0.69 0.20 0.34 0.92 -0.09 0.37 0.11 0.63 0.15 0.38 0.70 0.018000 0.36 0.12 0.63 0.16 0.35 0.88 0.00 0.20 0.00 0.57 0.18 0.18 0.76 0.00 0.28 0.00 0.61 0.18 0.27 0.80 0.00Average250 0.10 0.03 0.22 0.06 0.08 0.35 0.01 0.05 0.00 0.12 0.07 0.03 0.83 0.00 0.06 0.00 0.13 0.04 0.05 0.24 -0.01 0.12 0.03 0.23 0.06 0.11 0.37 0.02315 0.09 0.02 0.22 0.06 0.08 0.36 0.00 0.08 0.01 0.17 0.08 0.07 0.83 0.00 0.08 0.02 0.18 0.05 0.07 0.27 0.00 0.12 0.02 0.25 0.07 0.11 0.39 0.01400 0.10 0.01 0.28 0.08 0.09 0.37 0.00 0.12 0.03 0.26 0.09 0.11 0.83 0.01 0.12 0.03 0.26 0.07 0.11 0.40 0.00 0.16 0.04 0.34 0.09 0.14 0.42 0.01500 0.18 0.04 0.41 0.11 0.16 0.52 0.00 0.20 0.06 0.40 0.11 0.18 0.83 0.02 0.19 0.06 0.39 0.10 0.18 0.58 0.01 0.24 0.08 0.46 0.11 0.22 0.56 0.03630 0.27 0.07 0.55 0.15 0.24 0.73 0.02 0.30 0.11 0.56 0.15 0.26 0.85 0.06 0.30 0.10 0.55 0.14 0.27 0.88 0.04 0.33 0.11 0.59 0.14 0.32 0.77 0.07800 0.35 0.08 0.70 0.18 0.33 0.84 0.01 0.39 0.18 0.70 0.16 0.36 0.93 0.09 0.40 0.18 0.68 0.16 0.38 0.95 0.08 0.43 0.15 0.70 0.17 0.42 0.88 0.071000 0.43 0.13 0.73 0.18 0.42 0.91 0.01 0.48 0.24 0.79 0.15 0.46 0.91 0.14 0.49 0.25 0.78 0.15 0.48 0.91 0.14 0.52 0.23 0.78 0.16 0.53 0.86 0.121250 0.50 0.25 0.73 0.14 0.51 0.87 0.08 0.53 0.31 0.75 0.14 0.53 0.93 0.24 0.54 0.33 0.76 0.13 0.53 0.92 0.24 0.59 0.36 0.76 0.12 0.60 0.84 0.251600 0.54 0.33 0.76 0.14 0.55 0.85 0.20 0.57 0.34 0.76 0.13 0.58 0.94 0.14 0.58 0.35 0.77 0.13 0.59 0.94 0.14 0.61 0.40 0.75 0.11 0.62 0.87 0.262000 0.58 0.36 0.79 0.13 0.59 0.90 0.20 0.63 0.44 0.83 0.12 0.63 0.94 0.17 0.63 0.43 0.86 0.12 0.63 0.98 0.16 0.63 0.41 0.80 0.12 0.63 0.94 0.302500 0.71 0.49 0.92 0.13 0.71 0.99 0.40 0.70 0.51 0.91 0.12 0.70 0.99 0.33 0.70 0.52 0.91 0.12 0.69 0.99 0.32 0.72 0.52 0.93 0.12 0.73 0.98 0.423150 0.76 0.55 0.96 0.13 0.77 0.99 0.47 0.74 0.56 0.94 0.12 0.74 0.99 0.38 0.73 0.57 0.94 0.12 0.73 0.99 0.29 0.71 0.49 0.94 0.14 0.71 0.98 0.324000 0.74 0.48 0.96 0.14 0.75 0.99 0.39 0.71 0.46 0.95 0.16 0.73 0.98 0.13 0.71 0.45 0.95 0.16 0.72 0.98 0.04 0.67 0.43 0.95 0.17 0.68 0.98 0.155000 0.57 0.32 0.85 0.16 0.55 0.97 0.19 0.58 0.11 0.89 0.22 0.59 0.99 0.00 0.58 0.16 0.92 0.22 0.59 0.99 -0.02 0.52 0.28 0.79 0.17 0.50 0.93 0.106300 0.38 0.17 0.63 0.14 0.39 0.80 0.03 0.45 0.08 0.77 0.21 0.46 0.99 0.00 0.35 0.04 0.69 0.20 0.35 0.91 -0.05 0.36 0.11 0.63 0.15 0.37 0.71 0.018000 0.36 0.12 0.65 0.16 0.34 0.89 0.02 0.21 0.00 0.57 0.18 0.19 0.71 0.00 0.27 0.00 0.60 0.18 0.27 0.80 0.00190  A.6 Descriptive Statistics for Power Absorbance by System at Peak Pressure Mean, median, standard deviation, 5th – 95th percentile, maximum, and minimum power absorbance values listed across frequencies and grouped by trials and system at ambient pressure conditions.  Peak	Pressure:	RefWin Titan	Mean 5th	Percentile95th	PercentileS andard	DeviationMedian Max	Upper	Range	(Largest	Value)Mi 	Lower	Range	(Lowest	Value)Mean 5th	Percentile95th	PercentileStandard	DeviationMedian Max	Upper	Range	(Largest	Value)Min	Lower	Range	(Lowest	Value)Run	1250 0.14 0.05 0.28 0.07 0.12 0.34 0.01 0.13 0.04 0.24 0.06 0.12 0.40 0.02315 0.14 0.04 0.30 0.08 0.12 0.37 0.01 0.13 0.03 0.28 0.07 0.12 0.42 0.01400 0.18 0.05 0.38 0.10 0.16 0.43 0.02 0.18 0.04 0.36 0.09 0.16 0.44 0.01500 0.27 0.10 0.53 0.13 0.25 0.62 0.06 0.26 0.08 0.49 0.12 0.24 0.61 0.04630 0.38 0.13 0.73 0.17 0.36 0.80 0.09 0.36 0.12 0.66 0.15 0.34 0.78 0.08800 0.49 0.21 0.83 0.18 0.47 0.93 0.09 0.46 0.17 0.70 0.17 0.46 0.88 0.091000 0.57 0.29 0.84 0.16 0.59 0.95 0.11 0.54 0.25 0.79 0.15 0.55 0.86 0.141250 0.61 0.42 0.77 0.12 0.63 0.88 0.19 0.60 0.42 0.75 0.11 0.62 0.85 0.281600 0.61 0.44 0.78 0.11 0.62 0.90 0.25 0.61 0.43 0.75 0.10 0.62 0.92 0.282000 0.62 0.43 0.80 0.12 0.63 0.90 0.26 0.62 0.41 0.79 0.12 0.62 0.98 0.322500 0.72 0.51 0.91 0.12 0.71 0.98 0.45 0.71 0.51 0.91 0.12 0.72 0.97 0.453150 0.75 0.53 0.96 0.13 0.75 0.99 0.42 0.70 0.47 0.94 0.14 0.70 0.98 0.354000 0.69 0.45 0.94 0.16 0.70 0.98 0.36 0.65 0.37 0.95 0.18 0.66 0.98 0.005000 0.52 0.28 0.76 0.15 0.51 0.94 0.20 0.50 0.26 0.78 0.17 0.48 0.94 0.006300 0.37 0.17 0.60 0.13 0.37 0.74 0.10 0.35 0.11 0.63 0.15 0.35 0.74 0.008000 0.37 0.15 0.63 0.15 0.35 0.84 0.02 0.27 0.00 0.59 0.18 0.25 0.81 0.00Run	2250 0.13 0.03 0.27 0.07 0.12 0.38 0.01 0.13 0.04 0.24 0.06 0.12 0.35 0.02315 0.14 0.03 0.28 0.08 0.13 0.36 0.01 0.13 0.03 0.27 0.07 0.12 0.36 0.01400 0.17 0.04 0.36 0.10 0.16 0.41 0.02 0.18 0.04 0.35 0.09 0.16 0.47 0.02500 0.28 0.09 0.53 0.13 0.26 0.65 0.06 0.26 0.09 0.48 0.12 0.24 0.60 0.05630 0.38 0.13 0.70 0.17 0.35 0.84 0.09 0.36 0.13 0.65 0.15 0.34 0.78 0.07800 0.49 0.19 0.81 0.19 0.48 0.91 0.08 0.46 0.18 0.73 0.17 0.46 0.87 0.081000 0.57 0.27 0.82 0.16 0.57 0.91 0.08 0.55 0.26 0.78 0.15 0.55 0.89 0.141250 0.60 0.38 0.77 0.12 0.62 0.87 0.12 0.60 0.39 0.75 0.11 0.62 0.81 0.301600 0.60 0.40 0.77 0.11 0.61 0.81 0.27 0.60 0.42 0.75 0.10 0.61 0.82 0.272000 0.61 0.41 0.82 0.12 0.61 0.90 0.28 0.61 0.42 0.78 0.12 0.62 0.88 0.332500 0.71 0.52 0.92 0.12 0.71 0.98 0.43 0.70 0.50 0.91 0.12 0.71 0.97 0.373150 0.75 0.53 0.96 0.13 0.74 0.99 0.45 0.70 0.45 0.94 0.15 0.70 0.99 0.294000 0.70 0.44 0.95 0.15 0.71 0.99 0.37 0.67 0.41 0.94 0.17 0.66 0.98 0.285000 0.53 0.31 0.80 0.16 0.51 0.98 0.21 0.52 0.29 0.79 0.17 0.51 0.95 0.216300 0.38 0.18 0.60 0.14 0.37 0.75 0.01 0.37 0.11 0.62 0.15 0.37 0.71 0.018000 0.36 0.14 0.59 0.15 0.35 0.82 0.00 0.28 0.00 0.62 0.18 0.27 0.80 0.00Average250 0.13 0.04 0.28 0.07 0.12 0.36 0.01 0.13 0.04 0.24 0.06 0.12 0.37 0.02315 0.14 0.03 0.29 0.08 0.13 0.37 0.01 0.13 0.03 0.27 0.07 0.12 0.39 0.01400 0.18 0.04 0.37 0.10 0.16 0.42 0.02 0.18 0.04 0.36 0.09 0.16 0.45 0.01500 0.28 0.09 0.53 0.13 0.25 0.63 0.06 0.26 0.08 0.48 0.12 0.24 0.60 0.04630 0.38 0.13 0.72 0.17 0.35 0.82 0.09 0.36 0.12 0.65 0.15 0.34 0.78 0.08800 0.49 0.20 0.82 0.19 0.47 0.92 0.08 0.46 0.17 0.72 0.17 0.46 0.88 0.081000 0.57 0.28 0.83 0.16 0.58 0.93 0.09 0.55 0.26 0.78 0.15 0.55 0.87 0.141250 0.61 0.40 0.77 0.12 0.62 0.87 0.16 0.60 0.40 0.75 0.11 0.62 0.83 0.291600 0.61 0.42 0.77 0.11 0.61 0.85 0.26 0.61 0.43 0.75 0.10 0.61 0.87 0.282000 0.62 0.42 0.81 0.12 0.62 0.90 0.27 0.62 0.41 0.79 0.12 0.62 0.93 0.322500 0.72 0.51 0.92 0.12 0.71 0.98 0.44 0.71 0.51 0.91 0.12 0.71 0.97 0.413150 0.75 0.53 0.96 0.13 0.75 0.99 0.43 0.70 0.46 0.94 0.15 0.70 0.98 0.324000 0.69 0.45 0.94 0.15 0.70 0.99 0.36 0.66 0.39 0.94 0.18 0.66 0.98 0.145000 0.52 0.29 0.78 0.16 0.51 0.96 0.20 0.51 0.28 0.78 0.17 0.50 0.95 0.106300 0.37 0.17 0.60 0.14 0.37 0.75 0.06 0.36 0.11 0.62 0.15 0.36 0.73 0.018000 0.36 0.14 0.61 0.15 0.35 0.83 0.01 0.27 0.00 0.60 0.18 0.26 0.80 0.00191    Appendix B  Statistical Analaysis B.1 PA at Ambient Pressure Results of the mixed-model ANOVA investigating the effect of ethnicity, gender, ear, and instrument on power absorbance measurements at ambient pressure.  SS Degr. of (Freedom)MS F pIntercept 1714.628 1 1714.628 6604.577 0.000000Ethnicity 0.858 1 0.858 3.305 0.071072Gender 0.043 1 0.043 0.166 0.684433Ear 0.013 1 0.013 0.049 0.824327Error 38.682 149 0.260SYSTEM 1.258 3 0.419 21.476 0.000000SYSTEM*Ethnicity 0.052 3 0.017 0.887 0.447863SYSTEM*Gender 0.117 3 0.039 1.994 0.114091SYSTEM*Ear 0.090 3 0.030 1.537 0.204077Error 8.724 447 0.020FREQUENC 457.220 14 32.659 989.972 0.000000FREQUENC*Ethnicity 10.347 14 0.739 22.403 0.000000FREQUENC*Gender 3.525 14 0.252 7.633 0.000000FREQUENC*Ear 0.331 14 0.024 0.717 0.758821Error 68.816 2086 0.033SYSTEM*FREQUENC 5.706 42 0.136 24.774 0.000000SYSTEM*FREQUENC*Ethnicity 0.571 42 0.014 2.478 0.000000SYSTEM*FREQUENC*Gender 0.630 42 0.015 2.736 0.000000SYSTEM*FREQUENC*Ear 0.133 42 0.003 0.578 0.986903Error 34.319 6258 0.005 EffectRepeated Measures Analysis of Variance (Sheet1 in master data sheet_STATISTICA_june 4) for ALL systems at ambient pressure Sigma-restricted parameterization Effective hypothesis decomposition; Std. Error of Estimate: .5095214 192  B.2 Test-Retest Reliability - HearID Results of repeated measures mixed model ANOVA investigating test-retest reliability of PA measurements made by the HearID system.  SS Degr. of (Freedom)MS F pIntercept 894.9656 1 894.9656 5875.360 0.000000Ethnicity 0.0795 1 0.0795 0.522 0.471171Gender 0.0005 1 0.0005 0.003 0.954770Ear 0.0108 1 0.0108 0.071 0.790547Error 23.6104 155 0.1523TRIAL 0.0274 1 0.0274 4.045 0.046043TRIAL*Ethnicity 0.0165 1 0.0165 2.441 0.120243TRIAL*Gender 0.0002 1 0.0002 0.028 0.867139TRIAL*Ear 0.0229 1 0.0229 3.383 0.067788Error 1.0489 155 0.0068FREQUENCY 252.6748 14 18.0482 727.234 0.000000FREQUENCY*Ethnicity 4.1761 14 0.2983 12.020 0.000000FREQUENCY*Gender 1.2138 14 0.0867 3.494 0.000011FREQUENCY*Ear 0.2230 14 0.0159 0.642 0.831560Error 53.8542 2170 0.0248TRIAL*FREQUENCY 0.0445 14 0.0032 1.220 0.253341TRIAL*FREQUENCY*Ethnicity 0.0631 14 0.0045 1.732 0.043527TRIAL*FREQUENCY*Gender 0.0247 14 0.0018 0.676 0.799602TRIAL*FREQUENCY*Ear 0.0249 14 0.0018 0.683 0.792872Error 5.6503 2170 0.0026 Effect   193  B.3 Test-Retest Reliability – Otostat Results of repeated measures mixed model ANOVA investigating test-retest reliability of PA measurements made by the Otostat system.  SS Degr. of (Freedom)MS F pIntercept 906.4196 1 906.4196 6218.778 0.000000Ethnicity 0.0006 1 0.0006 0.004 0.947203Gender 0.0141 1 0.0141 0.097 0.755777Ear 0.0111 1 0.0111 0.076 0.782527Error 23.0293 158 0.1458TRIAL 0.0555 1 0.0555 9.005 0.003131TRIAL*Ethnicity 0.0031 1 0.0031 0.510 0.476311TRIAL*Gender 0.0090 1 0.0090 1.461 0.228607TRIAL*Ear 0.0068 1 0.0068 1.099 0.296137Error 0.9734 158 0.0062FREQUENCY 266.5088 15 17.7673 657.148 0.000000FREQUENCY*Ethnicity 5.5397 15 0.3693 13.660 0.000000FREQUENCY*Gender 1.2910 15 0.0861 3.183 0.000032FREQUENCY*Ear 0.2068 15 0.0138 0.510 0.936746Error 64.0775 2370 0.0270TRIAL*FREQUENCY 0.0531 15 0.0035 1.308 0.187897TRIAL*FREQUENCY*Ethnicity 0.0612 15 0.0041 1.510 0.093080TRIAL*FREQUENCY*Gender 0.0247 15 0.0016 0.609 0.870125TRIAL*FREQUENCY*Ear 0.0219 15 0.0015 0.539 0.919770Error 6.4106 2370 0.0027 Effect   194  B.4 Test-Retest Reliability – ReflWin Results of repeated measures mixed model ANOVA investigating test-retest reliability of PA measurements made by the ReflWin system.  SS Degr. of (Freedom)MS F pIntercept 860.7229 1 860.7229 6049.141 0.000000Ethnicity 0.2750 1 0.2750 1.933 0.166522Gender 0.4703 1 0.4703 3.305 0.071063Ear 0.0001 1 0.0001 0.001 0.975020Error 21.3433 150 0.1423TRIAL 0.0242 1 0.0242 2.032 0.156089TRIAL*Ethnicity 0.0202 1 0.0202 1.698 0.194565TRIAL*Gender 0.0011 1 0.0011 0.091 0.762931TRIAL*Ear 0.0131 1 0.0131 1.099 0.296231Error 1.7832 150 0.0119FREQUENCY 234.6848 15 15.6457 710.955 0.000000FREQUENCY*Ethnicity 7.6279 15 0.5085 23.108 0.000000FREQUENCY*Gender 2.9452 15 0.1963 8.922 0.000000FREQUENCY*Ear 0.3099 15 0.0207 0.939 0.519608Error 49.5147 2250 0.0220TRIAL*FREQUENCY 0.0987 15 0.0066 2.132 0.006744TRIAL*FREQUENCY*Ethnicity 0.0275 15 0.0018 0.595 0.881307TRIAL*FREQUENCY*Gender 0.0354 15 0.0024 0.765 0.718264TRIAL*FREQUENCY*Ear 0.0601 15 0.0040 1.298 0.194244Error 6.9416 2250 0.0031 Effect   195  B.5 Test-Retest Reliability – Titan Results of repeated measures mixed model ANOVA investigating test-retest reliability of PA measurements made by the Titan system.  SS Degr. of (Freedom)MS F pIntercept 998.4357 1 998.4357 6703.942 0.000000Ethnicity 0.1102 1 0.1102 0.740 0.391056Gender 0.3826 1 0.3826 2.569 0.110983Ear 0.1629 1 0.1629 1.094 0.297175Error 23.6803 159 0.1489TRIAL 0.0007 1 0.0007 0.151 0.697978TRIAL*Ethnicity 0.0028 1 0.0028 0.619 0.432601TRIAL*Gender 0.0298 1 0.0298 6.606 0.011079TRIAL*Ear 0.0120 1 0.0120 2.648 0.105651Error 0.7178 159 0.0045FREQUENCY 218.7266 15 14.5818 645.043 0.000000FREQUENCY*Ethnicity 10.0487 15 0.6699 29.634 0.000000FREQUENCY*Gender 3.0580 15 0.2039 9.018 0.000000FREQUENCY*Ear 0.5522 15 0.0368 1.628 0.059087Error 53.9151 2385 0.0226TRIAL*FREQUENCYY 0.1198 15 0.0080 4.571 0.000000TRIAL*FREQUENCY*Ethnicity 0.0122 15 0.0008 0.465 0.957913TRIAL*FREQUENCY*Gender 0.0176 15 0.0012 0.673 0.813118TRIAL*FREQUENCY*Ear 0.0298 15 0.0020 1.137 0.316506Error 4.1666 2385 0.0017 Effect 196  B.6 Power Absorbance Measurements made at Ambient vs. Tympanometric Peak Pressure  Results of the repeated measures mixed-model ANOVA investigating the effect of performing PA measurements at ambient pressure in comparison to peak tympanometric pressure (TPP).   Effect  SS Degr. of (Freedom) MS F p Intercept 3754.783 1 3754.783 7483.121 0.000000 {1}Gender 2.100 1 2.100 4.185 0.042588 {2}Ear 0.257 1 0.257 0.512 0.475557 {3}Ethnicity 1.529 1 1.529 3.047 0.083005 Error 73.258 146 0.502     {4}SYSTEMS 0.012 1 0.012 0.188 0.665230 SYSTEMS*Gender 0.009 1 0.009 0.138 0.710908 SYSTEMS*Ear 0.133 1 0.133 2.079 0.151504 SYSTEMS*Ethnicity 0.151 1 0.151 2.367 0.126120 Error 9.333 146 0.064     {5}PRESSURE 3.097 1 3.097 383.910 0.000000 PRESSURE*Gender 0.037 1 0.037 4.639 0.032903 PRESSURE*Ear 0.000 1 0.000 0.001 0.978533 PRESSURE*Ethnicity 0.069 1 0.069 8.506 0.004100 Error 1.178 146 0.008     {6}TRIALS 0.029 1 0.029 3.790 0.053478 TRIALS*Gender 0.018 1 0.018 2.406 0.123000 TRIALS*Ear 0.039 1 0.039 5.101 0.025391 TRIALS*Ethnicity 0.007 1 0.007 0.865 0.353933 Error 1.103 146 0.008     {7}FREQUENCY 804.566 15 53.638 751.983 0.000000 FREQUENCY*Gender 13.395 15 0.893 12.519 0.000000 FREQUENCY*Ear 0.730 15 0.049 0.682 0.804146 FREQUENCY*Ethnicity 34.643 15 2.310 32.379 0.000000 197  Error 156.209 2190 0.071     SYSTEMS*PRESSURE 1.803 1 1.803 249.497 0.000000 SYSTEMS*PRESSURE*Gender 0.007 1 0.007 1.004 0.318086 SYSTEMS*PRESSURE*Ear 0.001 1 0.001 0.169 0.681861 SYSTEMS*PRESSURE*Ethnicity 0.042 1 0.042 5.799 0.017280 Error 1.055 146 0.007     SYSTEMS*TRIALS 0.003 1 0.003 0.432 0.511872 SYSTEMS*TRIALS*Gender 0.022 1 0.022 3.197 0.075849 SYSTEMS*TRIALS*Ear 0.003 1 0.003 0.425 0.515367 SYSTEMS*TRIALS*Ethnicity 0.004 1 0.004 0.558 0.456274 Error 0.987 146 0.007     PRESSURE*TRIALS 0.004 1 0.004 0.979 0.324169 PRESSURE*TRIALS*Gender 0.003 1 0.003 0.795 0.374168 PRESSURE*TRIALS*Ear 0.007 1 0.007 1.830 0.178226 PRESSURE*TRIALS*Ethnicity 0.003 1 0.003 0.863 0.354345 Error 0.543 146 0.004     SYSTEMS*FREQUENCY 5.941 15 0.396 36.839 0.000000 SYSTEMS*FREQUENCY*Gender 0.091 15 0.006 0.562 0.905100 SYSTEMS*FREQUENCY*Ear 0.043 15 0.003 0.268 0.997631 SYSTEMS*FREQUENCY*Ethnicity 0.200 15 0.013 1.237 0.235667 Error 23.547 2190 0.011     PRESSURE*FREQUENCY 5.901 15 0.393 147.051 0.000000 PRESSURE*FREQUENCY*Gender 0.098 15 0.007 2.442 0.001527 PRESSURE*FREQUENCY*Ear 0.049 15 0.003 1.213 0.253691 PRESSURE*FREQUENCY*Ethnicity 0.177 15 0.012 4.410 0.000000 Error 5.859 2190 0.003     TRIALS*FREQUENCY 0.148 15 0.010 3.536 0.000005 TRIALS*FREQUENCY*Gender 0.044 15 0.003 1.047 0.402254 TRIALS*FREQUENCY*Ear 0.101 15 0.007 2.413 0.001762 TRIALS*FREQUENCY*Ethnicity 0.036 15 0.002 0.867 0.601466 Error 6.105 2190 0.003     SYSTEMS*PRESSURE*TRIALS 0.017 1 0.017 4.436 0.036895 4*5*6*1 0.003 1 0.003 0.669 0.414629 4*5*6*2 0.002 1 0.002 0.601 0.439435 198  4*5*6*3 0.007 1 0.007 1.678 0.197185 Error 0.574 146 0.004     SYSTEMS*PRESSURE*FREQUENCY 2.392 15 0.159 66.323 0.000000 4*5*7*1 0.011 15 0.001 0.310 0.994608 4*5*7*2 0.056 15 0.004 1.554 0.078876 4*5*7*3 0.075 15 0.005 2.088 0.008301 Error 5.265 2190 0.002     SYSTEMS*TRIALS*FREQUENCY 0.073 15 0.005 1.793 0.030259 4*6*7*1 0.033 15 0.002 0.814 0.663100 4*6*7*2 0.026 15 0.002 0.634 0.848577 4*6*7*3 0.011 15 0.001 0.262 0.997915 Error 5.936 2190 0.003     PRESSURE*TRIALS*FREQUENCY 0.008 15 0.001 0.619 0.861729 5*6*7*1 0.008 15 0.001 0.655 0.830574 5*6*7*2 0.022 15 0.001 1.754 0.035610 5*6*7*3 0.004 15 0.000 0.317 0.993935 Error 1.837 2190 0.001     4*5*6*7 0.049 15 0.003 4.028 0.000000 4*5*6*7*1 0.004 15 0.000 0.365 0.987099 4*5*6*7*2 0.007 15 0.000 0.558 0.907904 4*5*6*7*3 0.008 15 0.001 0.694 0.792804 Error 1.761 2190 0.001       199  B.7 Analysis of Covariance for Equivalent Ear Canal Volume Results of the analysis of covariance investigating equivalent ear canal volume measurements made by all four devices as continuous covariates in the original mixed-model ANOVA investigating the effect of instrument, gender, ethnicity, and ear on PA (Table B.1). Effect  SS Degr. of (Freedom) MS F p Intercept 32.28560 1 32.28560 186.0632 0.000000 ECV_1_Ref 2.07512 1 2.07512 11.9590 0.000721 ECV_1_HiD 1.41347 1 1.41347 8.1459 0.004972 ECV_1_Ot 0.18569 1 0.18569 1.0702 0.302692 ECV_1_T 2.52749 1 2.52749 14.5660 0.000202 Gender 0.38526 1 0.38526 2.2203 0.138457 Ethnicity 0.00227 1 0.00227 0.0131 0.909067 Ear 0.00410 1 0.00410 0.0236 0.878093 Error 24.29274 140 0.17352     SYSTEMS 0.00625 3 0.00208 0.1242 0.945793 SYSTEMS*ECV_1_Ref 0.75109 3 0.25036 14.9233 0.000000 SYSTEMS*ECV_1_HiD 0.17576 3 0.05859 3.4921 0.015741 SYSTEMS*ECV_1_Ot 0.06392 3 0.02131 1.2700 0.284210 SYSTEMS*ECV_1_T 0.27320 3 0.09107 5.4281 0.001136 SYSTEMS*Gender 0.02568 3 0.00856 0.5103 0.675413 SYSTEMS*Ethnicity 0.03370 3 0.01123 0.6695 0.571136 SYSTEMS*Ear 0.09938 3 0.03313 1.9746 0.117111 Error 7.04621 420 0.01678     FREQUENC 44.11954 14 3.15140 131.4224 0.000000 FREQUENC*ECV_1_Ref 1.54246 14 0.11018 4.5947 0.000000 FREQUENC*ECV_1_HiD 2.04287 14 0.14592 6.0853 0.000000 FREQUENC*ECV_1_Ot 0.56985 14 0.04070 1.6974 0.049879 FREQUENC*ECV_1_T 1.58176 14 0.11298 4.7117 0.000000 FREQUENC*Gender 2.09507 14 0.14965 6.2407 0.000000 FREQUENC*Ethnicity 3.90887 14 0.27921 11.6437 0.000000 200  FREQUENC*Ear 0.26017 14 0.01858 0.7750 0.697543 Error 46.99912 1960 0.02398     SYSTEMS*FREQUENC 0.55984 42 0.01333 2.8448 0.000000 SYSTEMS*FREQUENC*ECV_1_Ref 2.52179 42 0.06004 12.8144 0.000000 SYSTEMS*FREQUENC*ECV_1_HiD 0.60853 42 0.01449 3.0922 0.000000 SYSTEMS*FREQUENC*ECV_1_Ot 0.55492 42 0.01321 2.8198 0.000000 SYSTEMS*FREQUENC*ECV_1_T 0.50280 42 0.01197 2.5550 0.000000 SYSTEMS*FREQUENC*Gender 0.35849 42 0.00854 1.8217 0.000953 SYSTEMS*FREQUENC*Ethnicity 0.24220 42 0.00577 1.2307 0.146374 SYSTEMS*FREQUENC*Ear 0.06762 42 0.00161 0.3436 0.999977 Error 27.55101 5880 0.00469     B.8 Univariate Test of Significance for Equivalent Ear Canal Volume Results of the univariate test of significance investigating the effect of gender, ethnicity, ear and device used on equivalent ear canal volume measurements.   SS Degr. of (Freedom)MS F pIntercept 733.3702 1 733.3702 3655.404 0.000000Gender 4.9121 1 4.9121 24.484 0.000002Ethnicity 3.4405 1 3.4405 17.149 0.000058Ear 0.0108 1 0.0108 0.054 0.816820Error 29.0908 145 0.2006SYSTEMS 8.8535 3 2.9512 62.468 0.000000SYSTEMS*Gender 0.5867 3 0.1956 4.140 0.006546SYSTEMS*Ethnicity 0.3937 3 0.1312 2.778 0.040852SYSTEMS*Ear 0.3149 3 0.1050 2.222 0.084974Error 20.5507 435 0.0472 Effect 201  B.9 Univariate Test of Significance for Body Mass Index Results of the univariate test of significance investigating the effect of gender, ethnicity, and ear on body mass index values collected in the study. SS Degr. of (Freedom)MS F pIntercept 80812.25 1 80812.25 7651.236 0.000000Gender 145.34 1 145.34 13.760 0.000286Ethnicity 43.85 1 43.85 4.152 0.043231Ear 0.00 1 0.00 0.000 1.000000Error 1689.92 160 10.56 Effect        202  B.10 Analysis of Covariance for Body Mass Index  Results of the analysis of covariance investigating body mass index as a continuous covariate in the original mixed-model ANOVA investigating the effect of instrument, gender, ethnicity, and ear on PA (Table B.1). Effect  SS Degr. of (Freedom) MS F p Intercept 32.71471 1 32.71471 133.2061 0.000000 BMI 0.00040 1 0.00040 0.0016 0.967808 Gender 0.09617 1 0.09617 0.3916 0.532505 Ethnicity 0.73925 1 0.73925 3.0100 0.084984 Ear 0.04242 1 0.04242 0.1727 0.678352 Error 33.89208 138 0.24559     SYSTEMS 0.14336 3 0.04779 2.4664 0.061743 SYSTEMS*BMI 0.08804 3 0.02935 1.5146 0.210125 SYSTEMS*Gender 0.02627 3 0.00876 0.4519 0.716106 SYSTEMS*Ethnicity 0.07074 3 0.02358 1.2170 0.303131 SYSTEMS*Ear 0.06449 3 0.02150 1.1095 0.344985 Error 8.02151 414 0.01938     FREQUENC 11.23905 14 0.80279 24.5002 0.000000 FREQUENC*BMI 0.50847 14 0.03632 1.1084 0.344603 FREQUENC*Gender 3.03442 14 0.21674 6.6148 0.000000 FREQUENC*Ethnicity 8.40327 14 0.60023 18.3184 0.000000 FREQUENC*Ear 0.33494 14 0.02392 0.7301 0.745425 Error 63.30510 1932 0.03277     SYSTEMS*FREQUENC 0.51193 42 0.01219 2.2183 0.000011 SYSTEMS*FREQUENC*BMI 0.21007 42 0.00500 0.9103 0.636834 SYSTEMS*FREQUENC*Gender 0.41888 42 0.00997 1.8151 0.001022 SYSTEMS*FREQUENC*Ethnicity 0.50426 42 0.01201 2.1851 0.000016 SYSTEMS*FREQUENC*Ear 0.13056 42 0.00311 0.5658 0.989360 Error 31.84679 5796 0.00549    203  B.11 Resonance Frequency Results of the univariate test of significance investigating the effect of ear, gender, ethnicity, and number of trials on resonance frequency (measured by the Titan system) of participants in the study.  SS Degr. of (Freedom)MS F pIntercept 408941611 1 408941611 648.2191 0.000000Ear 154169 1 154169 0.2444 0.621759Gender 416 1 416 0.0007 0.979543Ethnicity 10179926 1 10179926 16.1363 0.000091Error 98415633 156 630869TRIALS 114749 1 114749 1.0560 0.305727TRIALS*Ear 83094 1 83094 0.7647 0.383216TRIALS*Gender 28636 1 28636 0.2635 0.608440TRIALS*Ethnicity 137767 1 137767 1.2678 0.261911Error 16952052 156 108667 Effect 204  B.12 Tympanometric Peak Pressure Results of the univariate test of significance investigating the effect of ear, gender, ethnicity, and number of trials on tympanometric peak pressure (measured by the Titan system) of participants in the study. SS Degr. of (Freedom)MS F pIntercept 25764.27 1 25764.27 92.42055 0.000000Ear 59.40 1 59.40 0.21306 0.645030Gender 984.02 1 984.02 3.52983 0.062164Ethnicity 1167.72 1 1167.72 4.18881 0.042392Error 42930.90 154 278.77TRIALS 105.34 1 105.34 1.44345 0.231426TRIALS*Ear 9.57 1 9.57 0.13117 0.717715TRIALS*Gender 81.11 1 81.11 1.11149 0.293409TRIALS*Ethnicity 68.98 1 68.98 0.94527 0.332452Error 11238.61 154 72.98 Effect  205  B.13 Static Admittance Results of the univariate test of significance investigating the effect of ear, gender, ethnicity, and number of trials on static admittance using 226 Hz tympanometry (measured by the Titan system) of participants in the study. SS Degr. of (Freedom)MS F pIntercept 77.56902 1 77.56902 229.4170 0.000000Ear 0.63747 1 0.63747 1.8854 0.171775Gender 1.17800 1 1.17800 3.4840 0.063915Ethnicity 2.51975 1 2.51975 7.4524 0.007094Error 50.71705 150 0.33811TRIALS 0.36997 1 0.36997 1.0058 0.317530TRIALS*Ear 0.37027 1 0.37027 1.0066 0.317331TRIALS*Gender 0.36741 1 0.36741 0.9988 0.319206TRIALS*Ethnicity 0.38153 1 0.38153 1.0372 0.310111Error 55.17606 150 0.36784 Effect 206  B.14 Reflectance Area Index Results of the univariate test of significance investigating the effect of ear, gender, ethnicity, and number of trials on reflectance area index (measured by HearID) of participants in the study. SS Degr. of (Freedom)MS F pIntercept 1062732 1 1062732 7932.884 0.000000Ear 16 1 16 0.120 0.729352Gender 117 1 117 0.875 0.351165Ethnicity 41 1 41 0.307 0.580253Error 20631 154 134TRIALS 33 1 33 5.680 0.018378TRIALS*Ear 10 1 10 1.714 0.192397TRIALS*Gender 0 1 0 0.023 0.879621TRIALS*Ethnicity 3 1 3 0.502 0.479562Error 902 154 6 Effect 207  B.15 Wideband Tympanometry Results of a mixed-model ANOVA investigating the effect of ethnicity, gender, and ear on average power absorbance between 375 – 2000 Hz using wideband tympanometry at various pressure levels (daPa) during WAI measurements.  SS Degr. of (Freedom)MS F pIntercept 3126.363 1 3126.363 1575.771 0.000000Gender 51.867 1 51.867 26.142 0.000001Ethnicity 29.884 1 29.884 15.062 0.000158Ear 3.427 1 3.427 1.727 0.190865Error 285.699 144 1.984PRESSURE 906.832 531 1.708 1494.976 0.000000PRESSURE*Gender 0.937 531 0.002 1.545 0.000000PRESSURE*Ethnicity 12.756 531 0.024 21.029 0.000000PRESSURE*Ear 0.480 531 0.001 0.791 0.999866Error 87.348 76464 0.001 Effect       208  B.16 Phase Angle Measured by ReflWin Results of the repeated measures mixed-model ANOVA investigating the effect of gender, ethnicity, ear, and trial number on reflectance phase angle (measured by ReflWin) in the study.  SS Degr. of (Freedom)MS F pIntercept 7451776 1 7451776 4432.906 0.000000Gender 4894 1 4894 2.911 0.090041Ethnicity 54013 1 54013 32.131 0.000000Ear 2107 1 2107 1.253 0.264724Error 252152 150 1681TRIALS 59 1 59 0.255 0.614434TRIALS*Gender 242 1 242 1.043 0.308675TRIALS*Ethnicity 3 1 3 0.011 0.915079TRIALS*Ear 15 1 15 0.065 0.799830Error 34845 150 232FREQUENC 11936407 15 795760 1244.478 0.000000FREQUENC*Gender 54222 15 3615 5.653 0.000000FREQUENC*Ethnicity 19462 15 1297 2.029 0.010821FREQUENC*Ear 1292 15 86 0.135 0.999968Error 1438724 2250 639TRIALS*FREQUENC 1641 15 109 1.252 0.224987TRIALS*FREQUENC*Gender 1156 15 77 0.881 0.585179TRIALS*FREQUENC*Ethnicity 4642 15 309 3.541 0.000004TRIALS*FREQUENC*Ear 486 15 32 0.371 0.986120Error 196646 2250 87 Effect   209   B.17 Admittance Magnitude Measured by ReflWin Results of the repeated measures mixed-model ANOVA investigating the effect of gender, ethnicity, ear, and trial number on admittance magnitude (measured by ReflWin) in the study.  SS Degr. of (Freedom)MS F pIntercept 1138158 1 1138158 10771.54 0.000000Gender 2778 1 2778 26.29 0.000001Ethnicity 548 1 548 5.19 0.024182Ear 148 1 148 1.40 0.239261Error 15850 150 106TRIALS 4 1 4 0.64 0.423510TRIALS*Gender 0 1 0 0.01 0.921718TRIALS*Ethnicity 2 1 2 0.22 0.636076TRIALS*Ear 3 1 3 0.49 0.482913Error 1018 150 7FREQUENC 263315 15 17554 1314.56 0.000000FREQUENC*Gender 1292 15 86 6.45 0.000000FREQUENC*Ethnicity 1227 15 82 6.12 0.000000FREQUENC*Ear 28 15 2 0.14 0.999963Error 30046 2250 13TRIALS*FREQUENC 44 15 3 1.66 0.051583TRIALS*FREQUENC*Gender 26 15 2 0.99 0.464739TRIALS*FREQUENC*Ethnicity 19 15 1 0.70 0.783049TRIALS*FREQUENC*Ear 15 15 1 0.56 0.907304Error 3969 2250 2 Effect  210   B.18 Phase Angle Measured by HearID Results of the repeated measures mixed-model ANOVA investigating the effect of gender, ethnicity, ear, and trial number on reflectance phase angle (measured by HearID) in the study.  SS Degr. of (Freedom)MS F pIntercept 7422.323 1 7422.323 1558.016 0.000000Gender 48.487 1 48.487 10.178 0.001723Ear 0.594 1 0.594 0.125 0.724457Ethnicity 1.969 1 1.969 0.413 0.521256Error 733.649 154 4.764TRIALS 0.659 1 0.659 0.687 0.408573TRIALS*Gender 0.228 1 0.228 0.237 0.626906TRIALS*Ear 0.015 1 0.015 0.015 0.902149TRIALS*Ethnicity 0.493 1 0.493 0.514 0.474704Error 147.824 154 0.960FREQUENC 2245.598 247 9.091 762.069 0.000000FREQUENC*Gender 18.886 247 0.076 6.409 0.000000FREQUENC*Ear 0.371 247 0.002 0.126 1.000000FREQUENC*Ethnicity 1.767 247 0.007 0.600 1.000000Error 453.794 38038 0.012TRIALS*FREQUENC 0.478 247 0.002 0.633 0.999999TRIALS*FREQUENC*Gender 0.102 247 0.000 0.135 1.000000TRIALS*FREQUENC*Ear 0.096 247 0.000 0.127 1.000000TRIALS*FREQUENC*Ethnicity 0.326 247 0.001 0.432 1.000000Error 116.305 38038 0.003 Effect  211   B.19 Comparison of ROC curves for 4 Instruments at 800 Hz The results of the analysis comparing ROC curves for test performance in distinguishing otoslcerotic ears at 800 Hz using normative data for all four instruments at ambient pressure and Interacoustics devices at peak tympanometric pressure.   Variable 1 HiD_800_Hz Variable 2 Ot_800_Hz Variable 3 Ref_Ambient_Pressure_800_Hz Variable 4 Ref_Peak_Pressure_800_Hz Variable 5 Titan_Ambient_Pressure_800_Hz Variable 6 Titan_Peak_Pressure_800_Hz Classification variable DIAGNOSIS Sample size 109 Positive group a 28 (25.69%) Negative group b 81 (74.31%) a DIAGNOSIS  = 1 b DIAGNOSIS  = 0 Variable AUC SE a 95% CI b HiD_800_Hz 0.689 0.0695 0.593 to 0.774 212  Ot_800_Hz 0.697 0.0687 0.602 to 0.782 Ref_Ambient_Pressure_800_Hz 0.632 0.0667 0.534 to 0.722 Ref_Peak_Pressure_800_Hz 0.822 0.0544 0.737 to 0.888 Titan_Ambient_Pressure_800_Hz 0.755 0.0623 0.663 to 0.832 Titan_Peak_Pressure_800_Hz 0.789 0.0581 0.700 to 0.861  a DeLong et al., 1988  b Binomial exact  Pairwise comparison of ROC curves HiD_800_Hz ~ Ot_800_Hz Difference between areas  0.00838 Standard Error a 0.0189 95% Confidence Interval -0.0287 to 0.0454 z statistic 0.443 Significance level P = 0.6577 HiD_800_Hz ~ Ref_Ambient_Pressure_800_Hz Difference between areas  0.0571 Standard Error a 0.0261 95% Confidence Interval 0.00588 to 0.108 213  z statistic 2.185 Significance level P = 0.0289 HiD_800_Hz ~ Ref_Peak_Pressure_800_Hz Difference between areas  0.133 Standard Error a 0.0333 95% Confidence Interval 0.0674 to 0.198 z statistic 3.984 Significance level P = 0.0001 HiD_800_Hz ~ Titan_Ambient_Pressure_800_Hz Difference between areas  0.0659 Standard Error a 0.0283 95% Confidence Interval 0.0104 to 0.121 z statistic 2.327 Significance level P = 0.0200 HiD_800_Hz ~ Titan_Peak_Pressure_800_Hz Difference between areas  0.0996 Standard Error a 0.0327 214  95% Confidence Interval 0.0355 to 0.164 z statistic 3.043 Significance level P = 0.0023 Ot_800_Hz ~ Ref_Ambient_Pressure_800_Hz Difference between areas  0.0655 Standard Error a 0.0303 95% Confidence Interval 0.00600 to 0.125 z statistic 2.158 Significance level P = 0.0309 Ot_800_Hz ~ Ref_Peak_Pressure_800_Hz Difference between areas  0.124 Standard Error a 0.0317 95% Confidence Interval 0.0622 to 0.186 z statistic 3.925 Significance level P = 0.0001 Ot_800_Hz ~ Titan_Ambient_Pressure_800_Hz Difference between areas  0.0575 215  Standard Error a 0.0254 95% Confidence Interval 0.00782 to 0.107 z statistic 2.268 Significance level P = 0.0233 Ot_800_Hz ~ Titan_Peak_Pressure_800_Hz Difference between areas  0.0913 Standard Error a 0.0295 95% Confidence Interval 0.0334 to 0.149 z statistic 3.094 Significance level P = 0.0020 Ref_Ambient_Pressure_800_Hz ~ Ref_Peak_Pressure_800_Hz Difference between areas  0.190 Standard Error a 0.0345 95% Confidence Interval 0.122 to 0.257 z statistic 5.497 Significance level P < 0.0001 Ref_Ambient_Pressure_800_Hz ~ Titan_Ambient_Pressure_800_Hz 216  Difference between areas  0.123 Standard Error a 0.0342 95% Confidence Interval 0.0560 to 0.190 z statistic 3.595 Significance level P = 0.0003 Ref_Ambient_Pressure_800_Hz ~ Titan_Peak_Pressure_800_Hz Difference between areas  0.157 Standard Error a 0.0356 95% Confidence Interval 0.0870 to 0.227 z statistic 4.404 Significance level P < 0.0001 Ref_Peak_Pressure_800_Hz ~ Titan_Ambient_Pressure_800_Hz Difference between areas  0.0668 Standard Error a 0.0259 95% Confidence Interval 0.0160 to 0.118 z statistic 2.576 Significance level P = 0.0100 217  Ref_Peak_Pressure_800_Hz ~ Titan_Peak_Pressure_800_Hz Difference between areas  0.0331 Standard Error a 0.0226 95% Confidence Interval -0.0113 to 0.0774 z statistic 1.462 Significance level P = 0.1438 Titan_Ambient_Pressure_800_Hz ~ Titan_Peak_Pressure_800_Hz Difference between areas  0.0337 Standard Error a 0.0103 95% Confidence Interval 0.0135 to 0.0540 z statistic 3.264 Significance level P = 0.0011  a DeLong et al., 1988      218  B.20 AUROC for 4 Instruments at 2000 Hz The results of the analysis comparing ROC curves for test performance in distinguishing otoslcerotic ears at 2000 Hz using normative data for all four instruments at ambient pressure and Interacoustics devices at peak tympanometric pressure.    Comparison of ROC curves Variable 1 HiD_2000_Hz  Variable 2 Ot_2000_Hz  Variable 3 Ref_Ambient_Pressure_2000_Hz  Variable 4 Ref_Peak_Pressure_2000_Hz  Variable 5 Titan_Ambient_Pressure_2000_Hz  Variable 6 Titan_Peak_Pressure_2000_Hz  Classification variable DIAGNOSIS 219  Sample size 109 Positive group a 28 (25.69%) Negative group b 81 (74.31%) a DIAGNOSIS  = 1 b DIAGNOSIS  = 0 Variable AUC SE a 95% CI b HiD_2000_Hz 0.629 0.0651 0.531 to 0.720 Ot_2000_Hz 0.627 0.0647 0.529 to 0.717 Ref_Ambient_Pressure_2000_Hz 0.673 0.0585 0.576 to 0.760 Ref_Peak_Pressure_2000_Hz 0.622 0.0664 0.524 to 0.713 Titan_Ambient_Pressure_2000_Hz 0.620 0.0678 0.522 to 0.712 Titan_Peak_Pressure_2000_Hz 0.644 0.0667 0.547 to 0.734  a DeLong et al., 1988  b Binomial exact  Pairwise comparison of ROC curves HiD_2000_Hz ~ Ot_2000_Hz Difference between areas  0.00265 Standard Error a 0.0274 95% Confidence Interval -0.0510 to 0.0563 220  z statistic 0.0967 Significance level P = 0.9230 HiD_2000_Hz ~ Ref_Ambient_Pressure_2000_Hz Difference between areas  0.0437 Standard Error a 0.0370 95% Confidence Interval -0.0289 to 0.116 z statistic 1.179 Significance level P = 0.2384 HiD_2000_Hz ~ Ref_Peak_Pressure_2000_Hz Difference between areas  0.00705 Standard Error a 0.0374 95% Confidence Interval -0.0662 to 0.0803 z statistic 0.189 Significance level P = 0.8502 HiD_2000_Hz ~ Titan_Ambient_Pressure_2000_Hz Difference between areas  0.00882 Standard Error a 0.0358 221  95% Confidence Interval -0.0614 to 0.0790 z statistic 0.246 Significance level P = 0.8055 HiD_2000_Hz ~ Titan_Peak_Pressure_2000_Hz Difference between areas  0.0150 Standard Error a 0.0361 95% Confidence Interval -0.0558 to 0.0857 z statistic 0.415 Significance level P = 0.6779 Ot_2000_Hz ~ Ref_Ambient_Pressure_2000_Hz Difference between areas  0.0463 Standard Error a 0.0423 95% Confidence Interval -0.0367 to 0.129 z statistic 1.094 Significance level P = 0.2740 Ot_2000_Hz ~ Ref_Peak_Pressure_2000_Hz Difference between areas  0.00441 222  Standard Error a 0.0403 95% Confidence Interval -0.0745 to 0.0833 z statistic 0.110 Significance level P = 0.9128 Ot_2000_Hz ~ Titan_Ambient_Pressure_2000_Hz Difference between areas  0.00617 Standard Error a 0.0347 95% Confidence Interval -0.0619 to 0.0742 z statistic 0.178 Significance level P = 0.8589 Ot_2000_Hz ~ Titan_Peak_Pressure_2000_Hz Difference between areas  0.0176 Standard Error a 0.0352 95% Confidence Interval -0.0515 to 0.0867 z statistic 0.500 Significance level P = 0.6168 Ref_Ambient_Pressure_2000_Hz ~ Ref_Peak_Pressure_2000_Hz 223  Difference between areas  0.0507 Standard Error a 0.0395 95% Confidence Interval -0.0268 to 0.128 z statistic 1.282 Significance level P = 0.1998 Ref_Ambient_Pressure_2000_Hz ~ Titan_Ambient_Pressure_2000_Hz Difference between areas  0.0525 Standard Error a 0.0434 95% Confidence Interval -0.0325 to 0.137 z statistic 1.210 Significance level P = 0.2264 Ref_Ambient_Pressure_2000_Hz ~ Titan_Peak_Pressure_2000_Hz Difference between areas  0.0287 Standard Error a 0.0427 95% Confidence Interval -0.0550 to 0.112 z statistic 0.672 Significance level P = 0.5018 224  Ref_Peak_Pressure_2000_Hz ~ Titan_Ambient_Pressure_2000_Hz Difference between areas  0.00176 Standard Error a 0.0411 95% Confidence Interval -0.0787 to 0.0823 z statistic 0.0429 Significance level P = 0.9657 Ref_Peak_Pressure_2000_Hz ~ Titan_Peak_Pressure_2000_Hz Difference between areas  0.0220 Standard Error a 0.0410 95% Confidence Interval -0.0582 to 0.102 z statistic 0.538 Significance level P = 0.5904 Titan_Ambient_Pressure_2000_Hz ~ Titan_Peak_Pressure_2000_Hz Difference between areas  0.0238 Standard Error a 0.00647 95% Confidence Interval 0.0111 to 0.0365 z statistic 3.678 225  Significance level P = 0.0002  a DeLong et al., 1988   

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