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Determining preferred listening levels of a personal listening device in teenagers and adults in real-life… Lane, Cheryl Nicole 2009

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DETERMINING PREFERRED LISTENING LEVELS OF A PERSONAL LISTENING DEVICE iN TEENAGERS AND ADULTS IN REAL-LIFE ENVIRONMENTS USING REAL-EAR MEASURES  by CHERYL NICOLE LANE B.Mus., The University of British Columbia, 2003  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE  in  The Faculty of Graduate Studies  (Audiology and Speech Sciences)  THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver)  March 2009  © Cheryl Nicole Lane, 2009  11  Abstract The aim for the current study was to determine whether the decibels (dB) of the Preferred Listening Levels (PLLs) for Personal Listening Devices (PLDs), as set by typical users in their daily acoustic environments, could potentially damage hearing. The PLDs of interest in this study were Apple iPods and MPEG Layer-3 audio (IVIP3) players. PLLs were determined by measuring real-ear levels at listeners’ reported typical listening levels for their own chosen musical stimuli. This design provided a clearer picture of subjects’ everyday listening experiences than previous research, as listeners may choose different PLLs for their own musical choices and everyday environments. These results could be used to increase public awareness of the real-world potential for hearing loss resulting from the use of PLDs, and to promote the adoption of guidelines to ensure a safe daily noise dose for consumers of recreational music. Seven male and six female PLD users with normal hearing kept a log of their average listening volumes, including listening durations at these levels, in three common listening environments (quiet, moderate, and public transit). The Fonix 7000 real-ear system was used to take the maximum and average measurements of the stimuli in the real ear. The resulting SPL value at the eardrum for the stimuli and the average listening duration for each environment were used to assess whether each subject was potentially damaging their hearing as a result of PLD use. We hypothesized that the average listening volumes and durations some subjects chose in real-life noisy situations would be sufficient to damage hearing. Specifically, we predicted that the Time Weighted Average Noise (TWAN) dose would be exceeded by some subjects. This prediction was only supported by the results for maximum (peak) dB (A) values, as one participant was exceeding the noise dose for maximum (peak) curves in noisy environments. However, this prediction was not supported by the results for average dB (A) values, which give a more accurate picture of participants’ PLLs, as no participants were exceeding the noise dose for  111  average curves in any environment. In conclusion, participants exhibited more conservative PLD listening behaviours than expected.  iv Table of Contents Abstract  ii  Table of Contents  iv  List of Tables  V  List of Figures  vii  Acknowledgements  viii  CHAPTER 1: 1.1 1.2 1.3 1.4 1.5  CHAPTER 2:  INTRODUCTION 1 STUDIES RELATING TO OCCUPATIONAL NOISE EXPOSURE 1 MUSICIANS AND NOISE EXPOSURE 3 EFFECTS OF RECREATIONAL NOISE (MUSIC) EXPOSURE 5 CHALLENGES OF A REALISTIC EXPERII\4ENTAL DESIGN 18 SUMMARY OF THE CURRENT STUDY’S EXPERIMENTAL DESIGN AND GOALS 21  2.1 2.2 2.3 2.4  METHODS PARTICIPANTS EQUIPMENT PROCEDURE DATA ANALYSIS PROCEDURE  23 23 23 25 29  3.1 3.2  RESULTS DESCRIPTIVE RESULTS STATISTICAL RESULTS  31 31 33  DISCUSSION DISCUSSION OF THE CURRENT STUDY’S RESULTS COMPARISON OF THE CURRENT STUDY’S RESULTS TO PREVIOUS STUDIES LIMITATIONS OF THE CURRENT STUDY IMPLICATIONS OF THE CURRENT STUDY’S RESULTS AND DIRECTIONS FOR FURTHER RESEARCH  53 53  CTER 3:  CHAPTER 4: 4.1 4.2 4.3 4.4  58 61 65 68  APPENDICES APPENDIX A: Consent Form APPENDIX B: Listening Log APPENDIX C: Questionnaire APPENDIX D: Raw Data Tables APPENDIX E: Ethics Certificate of Expedited Approval  74 74 79 84 88 124  V  List of Tables Table 3.1: Selected Questionnaire Responses  35  Table 3.2: dB (A) Levels for Quiet, Moderately Noisy and Noisy Environments, averaged across each Participant’s 3 Stimuli, Total Time in minutes (T) per day of Permissible Exposure at that Level, Total Time in minutes (Ta) per day of Actual Exposure (average), and Time Weighted Average Noise dose (TWAN)  38  Table 3.3: TWAN Dose per day, accounting for Participants’ Preferred Listening Level (PLL) and Listening Duration in each Environment, for Average Curves and Maximum (Peak) Curves  42  Table 3.4: Number of Song Samples per Musical Genre, listed per Male, Female, and Male and Female Participants  43  Table 3.5: Average dB (A) and dB SPL (Linear) per Genre in Quiet, Moderately Noisy and Noisy Environments, for the 4 Most Common Musical Genres from Music Sampled in this Study  44  Table 3.6: Average Volume Setting (%) in Different Environments  45  Table Dl: iPod 001 Raw Data for Quiet Environments  88  Table D2: iPod 001 Raw Data for Moderately Noisy Environments  89  Table D3: iPod 001 Raw Data for Noisy Environments  90  Table D4: iPod 002 Raw Data for All Environments  91  Table D5: iPod 003 Raw Data for Quiet Environments  92  Table D6: iPod 003 Raw Data for Moderately Noisy Environments  93  Table D7: iPod 003 Raw Data for Noisy Environments  94  Table D8: iPod 004 Raw Data for Quiet Environments  95  Table D9: iPod 004 Raw Data for Moderately Noisy and Noisy Environments  96  Table D10: iPod 005 Raw Data for Quiet Environments  97  Table Dli: iPod 005 Raw Data for Moderately Noisy Environments  98  Table D12: iPod 005 Raw Data for Noisy Environments  99  Table Dl 3: iPod 006 Raw Data for Quiet Environments  100  Table D14: iPod 006 Raw Data for Moderate Environments  101  vi Table D15: iPod 006 Raw Data for Noisy Environments  102  Table D16: iPod 007 Raw Data for Quiet Environments  103  Table D17: iPod 007 Raw Data for Moderate Environments  104  Table D18: iPod 007 Raw Data for Noisy Environments  105  Table D19: iPod 010 Raw Data for Quiet Environments  106  Table D20: iPod 010 Raw Data for Moderately Noisy Environments  107  Table D21: iPod 010 Raw Data for Noisy Environments  108  Table D22: iPod 013 Raw Data for Quiet Environments  109  Table D23: iPod 013 Raw Data for Moderately Noisy Environments  110  Table D24: iPod 013 Raw Data for Noisy Environments  111  Table D25: iPod 014 Raw Data for Quiet Environments  112  Table D26: iPod 014 Raw Data for Moderately Noisy Environments  113  Table D27: iPod 014 Raw Data for Noisy Environments  114  Table D28: iPod 015 Raw Data for Quiet Environments  115  Table D29: iPod 015 Raw Data for Moderately Noisy Environments  116  Table D30: iPod 015 Raw Data for Noisy Environments  117  Table D3 1: iPod 016 Raw Data for Quiet Environments  118  Table D32: iPod 016 Raw Data for Moderately Noisy Environments  119  Table D33: iPod 016 Raw Data for Noisy Environments  120  Table D34: iPod 017 Raw Data for Quiet Environments  121  Table D35: iPod 017 Raw Data for Moderately Noisy Environments  122  Table D36: iPod 017 Raw Data for Noisy Environments  123  vii List of Figures Figure 3.1: Percentage of the Maximum Volume Setting used for Volume Settings in Quiet, Moderate and Noisy Environments  46  Figure 3.2: Difference between dB (A) and Linear Frequency Weighting for Overall Level in dBSPL 47 Figure 3.3: Average PLLs for all Sampled Songs in dB SPL in Quiet, Moderate and Noisy Environments  48  Figure 3.4: The Effects of Environment and Frequency on dB SPL for Frequencies from 200 to 8000 Hz 49 Figure 3.5: dB SPL for Frequencies from 200 to 8000 Hz for Rap and Hip-Hop, Rock, Independent Rock/Alternative and Pop Musical Genres in Quiet Environments  50  Figure 3.6: dB SPL for Frequencies from 200 to 8000 Hz for Rap and Hip-Hop, Rock, Independent Rock/Alternative and Pop Musical Genres in Moderately Noisy Environments  51  Figure 3.7: dB SPL for Frequencies from 200 to 8000 Hz for Rap and Hip-Hop, Rock, Independent Rock/Alternative and Pop Musical Genres in Noisy Environments  52  viii Acknowledgements I would like to thank Dr. Navid Shahnaz and Dr. Lorienne Jenstad, my thesis supervisors, for their incredible support during my time working on this project. Their encouragement, knowledge and contributions of their precious time enabled me to overcome challenges that arose during the project, and to enjoy the research process. I would also like to thank Dr. Susan Small for her helpful comments and suggestions as a committee member. Thanks also to all of the faculty, staff, and my classmates at the school of Audiology and Speech Sciences for making graduate school a great experience. Finally, I’d like to thank my family, friends and colleagues for their support and helpfulness along the way.  1 Chapter 1: Introduction This chapter provides a review of the literature pertinent to an investigation of Preferred Listening Levels (PLLs) of iPods and MPEG Layer-3 audio (MP3) players for typical users, and any potential associated risk to hearing health. First, it will outline noise exposure topics from an occupational standpoint. Second, recreational noise exposure will be covered, including studies investigating noise exposure at discos, and from personal listening devices including portable tape cassettes and CD players. Third, studies relating to iPods and or MP3 players will be covered. Fourth, studies relating to behaviour and loud music listening will be outlined. Finally, the challenges of a realistic approach to the investigation of PLD use will be explored, followed by a description of the design of the current study.  1.1  Studies relating to Occupational Noise Exposure Noise induced hearing loss (NIHL) accumulates gradually with any type of noise  exposure yet is more readily recognized as an occupational than a recreational health hazard (Clark, 1992). An extensive scientific and governmental literature regarding occupational noise exposure and NIHL exists, enabling employers, workers and healthcare providers among others to inform themselves of relevant risks and policies for prevention and treatment. Additionally, an international standard, ISO 1999, was developed in 1990 and describes calculations used to determine NIHL risk according to factors including age, gender and noise exposure history (as cited in Clark, 1992). No such standard has been developed regarding recreational noise exposure to date, perhaps because of the lack of scientific consensus on the prevalence of recreational NIHL. The Occupational Health and Safety Regulations (B.C. Reg. 382/2004, s.1) of the British Columbia Worker’s Compensation Act outline workplace noise exposure limits. These regulations state that workers should not be exposed to noise levels above either 85 dB (A) level  2 of exposure (Lex) per day, or 140 dB (C) peak sound level. In this regulation Lex refers to the limit of permissible exposure to a steady noise level for an eight-hour work day; dB (A) refers to an approximation of the 40-phon equal loudness contour; dB (C) refers to an approximation of the 1 00-phon equal loudness contour; and peak sound level refers to the maximum SPL of an impulse sound. The BC regulations use a 3 dB exchange rate; that is, for every 3 dB (A) increase in sound level, the allowable listening duration should be halved. These regulations are consistent across all Canadian provinces except Quebec, which permits a 90 dB(A) Lex daily noise exposure level with a 5 dB(A) exchange rate (Act Respecting Occupational Health and Safety, [R.S.Q., c.2. 1]). In the United States, noise exposure regulations include those put forth by both the U.S. National Institute for Occupational Safety and Health (NIOSH) and the U.S. Occupational Safety and Health Administration (OSHA). NIOSH states that workers should not be exposed to noise exceeding 85 dB (A) for an eight-hour time-weighted average, with a 3 dB exchange rate (NIOSH, 1972; NIOSH 1998). In contrast, OSHA states that workers should not be exposed to noise exceeding 90 dB (A) for an eight-hour time-weighted average, with aS dB exchange rate (OSHA, 1981). Additionally, OSHA put forth an amendment stating that employers must make a hearing conservation program available to workers who are exposed to a level of 85 dB (A) or greater (OSHA, 1983). Similar guidelines could be adopted for exposure levels to recreational music.  3 1.2  Musicians and Noise Exposure For musicians, music of sufficient intensity and duration is itself an occupational health  hazard. Studies on occupational noise exposure in musicians provide a link between the topics of noise exposure and recreational noise exposure resulting from overly amplified music. Professional musicians are susceptible to gradual hearing loss (Chasm, 1996), consistent with NIHL. Long exposures and high music levels are hazards for professional musicians. The following section outlines the findings of several important studies that investigated occupational noise exposure in musicians. Orchestral musicians need to hear well during rehearsals and performances and preserve their hearing. Royster, Royster, & Killion (1991) investigated sound exposure and hearing thresholds in orchestral musicians to assess potential risks to hearing. Fifty-nine musicians volunteered to have their hearing tested. All audiograms were obtained before the day’s work began to avoid contamination by temporary threshold shifts (TTSs). Next, using personal dosimeters set to a 3 dB exchange rate, 68 noise measurements of 44 volunteer musicians’ sound exposures were made throughout the orchestra’s performance space. Results showed a range of Leq values between 79-99 dB (A) and a mean of 89.9 dB (A). Musicians’ corresponding daily Leqs for an 8 hour exposure period were calculated based on 15 hours of music exposure on the job per week, not including practicing and playing off the job. The calculated Leqs were between 75-95 dB (A) with a mean of 85.5 dB (A). Notably, 52.5% of tested musicians showed audiometric notches that were consistent with NIHL. The 32 musicians who had both audiograms and noise measurements completed showed correlations between their hearing threshold levels between 3-6 kHz and their personal Leqs. A significant limitation of this study is that off-the-job noise exposure including individual practice time was not measured for the majority of participants. When frequent off-the-job activities such as individual practice, teaching, jobs with other musical groups and music listening are taken into account it can be  4 assumed that the upper limit of the Leq distribution for on-the-job and off-the-job playing would be considerably higher than the on-the-job range given in the study (Royster et al., 1991). Music is a unique noise exposure source. Thiery and Meyer-Bisch (1987) found that the combination of transient noises and continuous noise in music increases the risk of hearing loss above the risk associated with the continuous noise level alone. In a recent review of the literature on orchestral musicians’ risk of noise exposure, Behar, Wong and Kunov (2006) noted that music differs from most industrial noise as a noise exposure source primarily because it has continual non-cyclical changes in intensity and spectrum. Additionally, duration of exposure changes constantly, including stops, starts, and repetitions depending on the musical program to be performed (Behar et al., 2006). Number and types of instruments, as well as stage setups, also vary among musical selections. These variables make the estimation of music exposure a difficult task. The studies discussed in the review included the following: Beale (2002), Boasson (2002), Eaton & Gillis (2002), Fleischer & Muller (2005), Kahari, Axelsson, Hellstrom & Zachau (200la), Kahari, Axelsson, Helistrom & Zachau (2001b), Laitinen, Toppila, Olkinuora & Kuisma (2003), Lee, Behar, Kunov & Wong (2005), McBride et al. (1992), Mikl (1995a), Mild (1995b), Obeling & Poulsen (1999) and Williams (1995). Overall, Behar et al. (2006) concluded that studies in their review indicated minimal to low risk for hearing loss due to occupational noise exposure among orchestral musicians. Nevertheless, they cited that unclear calculations of estimated orchestral performance time were a common limitation among studies. Musical genre can play a role in the dB (A) levels during performances. Upper limits of sound levels measured in numerous orchestras are between 83-112 dB (A) (Hart, Geitman, Schupbach & Santucci, 1987). Musicians performing music from other genres are similarly exposed to high levels including 100-115 dB (A) at a rock band performance in a concert hall (Tan, Tsang & Wang, 1990), and 80-101 dB(A) measured on stage in blues, jazz and country bands (Chasm, 1996).  5 It has been noted that although gradual hearing loss occurs in musicians with music induced hearing loss (MIlL), it is the often accompanying tinnitus and less common pitch perception problems that are most disruptive to both musical performance and enjoyment (Chasm, 1996). Suggestions to limit music exposure among professional musicians have been put forth by experts in the hearing health care community. Such suggestions include the use of hearing protection, practice mutes, and making environmental or positional modifications appropriate for each musician and instrument (Chasm, 1996). Weighting systems such as dB (A) are based upon equal loudness contours in order to provide approximate loudness measures for complex sounds (Aarts, 1992). Although music is predominantly composed of high frequency energy, low frequency energy is often present in a variety of musical genres, and contributes more greatly to loudness perception in music at higher levels just as it does in norimusical complex sounds. Therefore, when taking measurements of loud music levels it may be more appropriate to use the dB (C) weighting system. The dB (A) weighting system attenuates low and very high frequencies and may be an appropriate curve for music measurements at low levels, but may be less appropriate for measurements at levels above 40 dB SPL at 1000 Hz. However, measurements of music levels in the free field have most commonly been made using a dB (A) weighting system primarily in an attempt to interpret music exposure results using existing industrial noise exposure guidelines. A further argument that has been used to justify the use of the dB (A) weighting system is that low frequencies are not as dangerous as other frequencies in causing structural or metabolic damage to the organ of Corti (Bohne & larding, 2000).  1.3  Effects ofRecreational Noise (Music) Exposure Recreational noise exposure sources, or music exposure sources as is the case for this  review, include both free field sources such as clubs, and personal listening devices such as MP3  6 players and iPods. This section will highlight studies that examine these sources using a variety of data collection techniques including focus groups, literature review, questionnaires and real ear measurements. Findings from studies that employ the latter two techniques are of particular interest as both are used in the current study. The use of online questionnaires in studies regarding music and hearing damage enables researchers to collect data from a large number of individuals who might otherwise be difficult to recruit for an audiological laboratory session. Chung, Des Roches, Meunier, and Eavey (2005) performed a web-based survey on young adults regarding NIHL. Results showed that a majority (6 1%) of the 9693 respondents have experienced tinnitus or hearing impairment after exposure to loud music at concerts (6 1%). Although only 14% reported previous earplug use at music venues, a number of participants could be motivated to use earplugs if alerted to a potential for permanent hearing loss (66%), or advised to do so by a health professional (59%). Although this study did not provide objective data, it did yield insight into adolescents’ motivations to protect their hearing in an unobtrusive manner. Information about typical PLD users’ listening habits, including subjective volume setting information, was gathered by Zogby (2006), who was commissioned by the American Speech-Language-Hearing Association (ASHA) to administer a large scale survey to 1000 adults  and 301 teenagers pertaining to use of personal electronic devices and headphones. Results indicated that over 61% of adolescents and 23% of adults claimed to own an Apple iPod or MP3 player. Data from the Zogby survey showed that both adults and high-school students are unlikely to purchase noise-reduction headphones as a strategy to prevent hearing loss from the use of PLDs. The Zogby survey showed that 30% of teens and 38% of adults listen to their iPods 1-4 hours a day, whereas 41% of teens listen between 30 minutes and 1 hour a day. Regarding listening volume for Apple iPods in particular, 38% of adults and 41% of students prefer to set the devices to loud levels. Additionally, 13% of students and only 6% of adults  7 were likely to set the devices to very loud levels (Zogby, 2006). A major strength of this study is the large number of survey participants. A drawback to its survey-only design is that objective data was not obtained on any participants. Thus, one cannot conclude for certain what levels correspond to a given reported typical volume setting. At the current time, the application of workplace noise exposure limits to appropriate PLD outputs is common. Recently, the European Conmiission asked the Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR) to evaluate by way of a large scale literature review whether or not PLDs are likely to cause hearing loss if used at levels below 80 dB (A), in accordance with current European Noise at Work Regulations (SCENIHR, 2008). SCENIHR was also asked to determine an appropriate output limit for the devices if it did find PLDs to be a health risk, considering the levels, duration and frequency of exposures for PLD users. SCENIHR concluded that based on workplace noise exposure research it is unlikely that exposure to PLDs at levels below 80 dB (A) is hazardous to hearing no matter the duration of regular exposure. The report stated that it was uncertain whether this cutoff level was safe for children. For levels above 80 dB (A) it was recommended that calculation of safe listening levels be based on the 3 dB exchange rate, albeit cautiously as the study noted limited research on the topic of PLDs and associated hearing loss among users. Additionally, it was mentioned that other sources of noise could impact the appropriateness of the resulting safe level calculation. Currently in the European Union, maximum PLD output is limited to 100 dB with the stock headphones designed for the device (Bistrup, Babisch, Stansfeld & Sulkowski, 2006). SCENIHR recommended that future research should include investigation of typical current patterns of PLD use, duration and preferred listening levels (SCENIHR, 2008). The recommendations of the report are sensible in that they take into account the variability of PLD users’ noise exposure histories and typical patterns of use. However, it is important to specify that such calculations will be more accurate if they take into account the different PLEs users  8 choose in a variety of listening environments. As the scientific literature on the topic of hearing loss associated with PLD use expands it is possible that noise exposure calculations and further regulations specific to and more appropriate for music exposure will be developed. It is in the interest of the hearing healthcare community to determine which detrimental hearing related adolescent behaviours might be adaptable. Vogel, Brug, Hosli, Van Der Plog and Rant (2008) investigated potentially modifiable determinants for behaviour regarding noise or music exposure in adolescents using focus groups and surveys. Due to a lack of studies on the topic, the researchers held focus groups on loud music and MP3 players with adolescents in order to obtain their opinions and determine what aspects of their behaviour could be altered. Participants were chosen and assigned to groups according to findings from a review of the literature conducted by Vogel, Brug, Hosli, Van Der Plog and Rant (2007), who noted that the primary sociodemographic correlates of protective and risk taking behaviours in young people aged 12 to 25 years old were age, sex, and education level. Semi-structured questions in the 2008 study were inspired by the protection motivation theory, which posits that an individual’s health precautionary behaviours depend on factors that are both personal and environmental. Results indicated that most participants played their PLDs at maximum volume, particularly males in prevocational schools. Although most adolescents were aware that loud music exposure posed a risk to their hearing, they felt personal risk was unlikely and were unwilling to allow others to mediate their listening habits. The authors concluded that interventions should include providing adolescents with information on loud music exposure risks to hearing and strategies to reduce risk. Additionally, they stated that volume guidelines may be an important solution. The recent development of MP3 players and iPods has created a need to assess and discuss current hearing protective attitudes and behaviours among individuals who typically use the devices. Motivation and behaviour relating to loud music exposure is an important area of investigation in  9 this field as it can help us to determine appropriate strategies for hearing conservation education related to PLDs. If PLD users become more numerous it follows that the number of individuals who exhibit extremely maladaptive listening habits would also increase. Florentine, Hunter, Robinson, Ballou and Buus (1998) created and administered the Northeastern Excessive Music Listening Survey to 90 participants in order to investigate behaviours of individuals who listen to overly loud music. Results showed that 8 out of 90 individuals scored in a range indicative of maladaptive music listening (MML) habits. These individuals continued their listening habits despite known cochlear damage. Such habits are similar in nature to those seen in individuals exhibiting substance abuse. It is possible that listeners who score in this range have a subjective sense of addiction to overly loud music. For individuals whose scores fall in this group, information about the hazards of continued excessively loud music exposure is not useful, although information about how to stop such exposures might be (Florentine et al., 1998). One limitation of the study is that those subjects who scored within the range of MML could not be diagnosed as having a disorder as they were not interviewed by a certified clinical psychiatrist or psychologist. Thus further research should be conducted to confirm the presence of MML. Dangerous output levels can be reached when PLDs are used in combination with certain headphone styles (Fligor & Cox, 2004). Fligor and Cox performed a study on the output levels of portable compact disc (CD) players and potential hearing damage risk. A white-noise standard signal was played through various headphones styles (including inserts, verticals, supra aurals, and circumaurals) placed in or over the ear canals of a Knowles Electronics Manikin for Acoustic Research (KEMAR). Output levels for several volume settings were recorded via KEMAR microphones and compared to output levels of music selections taken from eight different musical genres. Findings demonstrated that free-field equivalent sound pressure levels (SPL) reached 91 to 121 dB (A) when measured at maximum volume settings, and that this  10 output level was increased by 7 to 9 dB with the use of insert earphones in place of the supra aural stock headphones provided with the devices. Headphone output levels varied across manufacturer and style of headphone. However, smaller headphones tended to produce higher outputs. Using the United States of America National Institute for Occupational Safety and Health (OSHA) noise dose model, results indicated that with the volume control set to less than 70%, individuals using an earbud headphone style would reach a maximum noise dose within 1 hour or less (Fligor & Cox, 2004). Unfortunately, this study did not include MP3 players or iPods, nor was it within its scope to assess the PLLs of individuals who use them. Because many individuals are still using earbud style headphones with PLDs such as MP3 players and iPods, it remains important to study these devices in combination. PLD volume settings have been studied in multiple ways. LaRouere and LaRouere (2007) conducted an investigation to determine the volume levels in relation to currently recommended safe levels at which teenagers listen to their iPods. The study employed a calibrated measuring device that enabled measurement of the volume setting in percentages, because iPods display no numerical volume setting indication. Measurements were taken at three intervals during a 20-minute listening period. Results demonstrated that all 15 participants listened at volumes which fell within the safe listening recommendations at least once during the 20 minute session, although by the end of the session one third of participants had exceeded the recommended volume. These results imply that some individuals increase the volume the longer they listen during a given listening session. It is possible that a listening session in a laboratory may not represent a typical listening session for a given participant, and that PLLs may likewise be atypical of that participant. Relationships between frequency of PLD use and auditory thresholds have been identified and are cause for concern (Meyer-Bisch, 1996). In a study that examined both audiometric and questionnaire data, Meyer-Bisch analyzed results from an audiometric survey on  11 1364 participants regarding exposure to highly amplified music and hearing damage. Volunteers also filled out noise exposure questionnaires and had their hearing tested with automatic audiometers in portable sound booths set up in a town square. These audiometers could test 449 frequencies between 125 and 16 000 Hz, although only frequencies above 500 Hz were tested due to low frequency noise interference in the environment. Use of the automatic audiometers allowed the investigator to detect notches between conventional frequencies, which are important for detecting NIHL. Results showed that individuals who listened to personal tape cassette players with headphones more than 7 hours per week (54 participants) had a statistically significant hearing threshold increase compared to those who listened between 2 and 7 hours per week (195 participants). However, Meyer-Bisch speculated that some individuals may have more fragile ears than others, just as Serra et al. (2005) speculated a decade later. Conclusions such as these justify a cautious approach to noise exposure for all, particularly those who experience signs of damage such as tinnitus or auditory fatigue (Meyer-Bisch, 1996). Although this study found that frequency of PLD use is related to audiometric threshold, it is not known what real-ear levels were associated with PLD use of more than seven hours per week. As such the strength of the conclusion is limited by the fact that no real-ear measurements were taken. In a similar study, Peng, Tao and Huang (2007) investigated the risk of hearing damage resulting from the use of MP3 players as well as Walkman cassette players and CD players in young adults with normal hearing. The authors included both conventional and extended high frequency audiometric tests for 120 PLD users and 30 non PLD users. Participants were categorized as belonging to one of three subgroups based on the duration in years of PED use. Results indicated worse thresholds for PLD users. Notably, listeners who had a longer history of PLD use demonstrated increased thresholds across broader frequency ranges. Peng et al. concluded that long term use of PLDs could be hazardous to hearing. One significant drawback of this study is the reliance upon self-reports to determine PLD listening habits. Where possible,  12 objective measures are preferable and can provide more information regarding the likelihood that PLDs are the primary cause of any hearing damage. Some studies have combined surveys with real or simulated real-ear measurements. Biassoni et al. (2005) and Serra et al. (2005) conducted a four-year longitudinal study on the effects of recreational noise exposure among adolescents aged 14 to 17 years old. One-hundredand-six adolescents took part in the study. In Part I of the report (Serra et al., 2005) they describe the measurements obtained. The study was prompted in order to investigate the potential audiologic etiology of the high percentage of hearing loss among young people in Argentina at the beginning of their working careers, despite no explanatory medical history. Only results from adolescents with normal hearing at the beginning of the study were included in the final analysis. Conventional and extended high frequency audiometry, psychosocial measurements, and music exposure sound level measurements were performed annually. Psychosocial measurements gathered information relating to attitudes, behaviours and activities relevant to noise exposure. Sound level measurements were made at discos using miniaturized measuring instruments and noise dosimeters. Measurements of PLD output for participants who normally used the devices were made using an IEC 60959 standard approved manikin with ear occluders in order to achieve average ear canal levels. Participants were asked to set their PLDs to their typical listening volume for 2 or 3 of their favourite songs. It is not clear whether the participants’ own headphones were placed on the manikin once participants had adjusted the PLD to their PLL. However, it seems likely that participants’ headphones were used for the simulated real-ear measurements, since Serra et al. describes placement of “the same musical device” on the manikin (p. 67). Once the device was placed on the manikin, recordings were made at the resulting volume settings using a 2 channel real-time real-ear analyzer in third octave bands. Each channel was analyzed separately to account for stereo differences between ears. Results for the manikin measurements ranged between 75 to 105 dB (A) Leq for minimum and  13 maximum levels respectively (Serra et al., 2005). Such levels imply a hearing risk for some individuals, particularly for longer listening durations. Serra et al. (2005) also took disco sound level measurements of the highest equivalent Aweighted sound levels (dB (A) Leq) which ranged from 104.3 to 112.4 dB (A) Leq with peaks up to 117.5 dB (A) Leq for the quietest to loudest discos sampled respectively. At the quietest disco, the noise dose calculated for four exposure hours was 1600% of the maximum safe daily noise dosage. While the noise dose for all discos exceeded the maximum safe noise dose, it should be noted that adolescents who visit discos weekly or biweekly will have more recovery time between these exposures than individuals in occupational environments. However, most adolescents are likely to participate in other noisy activities apart from attendance at discos. Measured PLD levels were mostly lower than disco levels, and ranged from 75-105 dB (A) Leq. PLD listening durations were generally shorter than disco attendance durations. In general, results showed that of all noisy activities examined, attendance at discos posed the greatest threat to participants’ hearing health (Serra et al., 2005). In Part II of the report, Biassoni et al. (2005) discuss some significant hearing threshold shifts observed during the study’s third year. Participants with larger shifts were described as members of subgroup 2. Compared to subgroup 1, subgroup 2 had slightly worse hearing threshold levels in the first year of the study in both mid and high frequencies, and larger threshold shifts during the  Id 3  year. Participants in subgroups 1 and 2 were thus described as  having ‘tough ears’ and ‘tender ears’, respectively. Although participation in noisy recreational activities generally increased among all participants throughout the study period, such participation increased most for subgroup 2. Biassoni et al. concluded that the same sound levels can damage some ears more than others, making a participant’s classification in the ‘tender ears’ versus ‘tough ears’ an important factor in the prediction of hearing damage risk. Limitations of the study included the use of simulated real-ear rather than actual real-ear measurements and the  14 use of one listening environment (quiet) for PLL adjustment. Although simulated real-ear measurements made with a manikin allow direct comparison of PLD volume settings among participants, they do not account for individual ear canal differences which may influence typical volume settings. To illustrate, Saunders and Morgan (2003) showed that for 1814 ears the distribution of eardrum dB SPL varied across frequencies and ears by as much as 40 dB for a fixed signal level. The simulated real-ear data is further limited in that PLLs represent PLLs in quiet situations only. The portable nature of PLDs allows users to listen to the device in a variety of listening environments. The following study includes real-ear measurements yet does not address the issue of listening environment directly. Torre (2008) surveyed 1016 University students regarding PLD listening habits and use. Results demonstrated that 930 of the 1016 university students respondents (91.5%) used PLDs; of these, >50% listen to their PLDs 1-3 hours and >90% reported using their PLDs at medium and loud volume. Additionally, for 32 participants, measurements of the dB SPL value in the ear canal were taken for blindly set volume settings corresponding to four loudness categories in quiet surroundings. The four loudness categories were intended to correspond to survey responses concerning reported listening volume categories. The mean SPL values for medium and loud levels were 71.6 and 87.7 dB SPL, respectively. Torre also found that the trend for the duration and level of PLD use varies between males and females and among ethnic groups. Considering the above reported listening durations and ear canal dB SPL values, PLDs may not pose a risk to hearing for the majority of listeners. However, Torre acknowledged that the real-ear levels may underestimate the levels experienced by listeners in most everyday listening environments where some noise is present. Hence, results from real-ear measurements of PLLs are most realistic in a study design that takes into account the effects of background noise on PLLs. A further limitation of the study is that participants used different styles of earphones for the PLD measurements. Depending on  15 participants’ headphone styles it is possible that some participants’ PLLs varied as a result of headphone style, although all measurements were made in a quiet environment. For instance, Hodgetts, Rieger & Szarko (2007) reported a significant difference in PLLs for earbud versus over-the-ear headphones with noise reduction in a simulated quiet environment. Commuting with PLDs on public transit has become commonplace. Because public transit can be a noisy environment in which many individuals spend a great deal of time it is important to recognize that this environment can have an impact on listening habits, as shown by Hodgetts et al. (2007). Some examples of noise levels from public transit can be found in a report on the impact of transit buses in the city of Vancouver, which describes measurements taken with a sound level meter held at waist level to determine the levels of buses passing by at full acceleration (City of Vancouver Bus Impact Task Force, 2000). Trolley, natural gas and diesel buses produced levels of<50, 75 and 83 dB (A), respectively. Although the report focused on street level noise, the noise exposure on a transit bus has been examined by Worksafe BC (2008) which reported that a school bus driver of a gas-run bus has a daily noise exposure level of 83 dB (A) Lex. Hence, although transit riders would not typically ride the bus or other vehicle for 8 hours a day it can be nonetheless a noisy environment, particularly for listening to music. Inclusion of real-ear measurements in a study on PLD use raises the question of what music should be used as the stimulus. In the study described above, Torre (2008) chose only one song clip to be the same stimulus for all of their participants. Hodgetts et al. (2007) likewise chose a single song to be the stimulus, partly because the particular song had limited amplitude fluctuations. In their research, Hodgetts et al. investigated the influence of headphone style and listening environment on normal hearing adults’ preferred listening levels (PLLs) while using an MP3 player. They measured PLLs for an MP3 player as set by subjects in a laboratory in simulated background noise conditions. The researchers reported that the MP3 player used, a  16 Creative MuVo N200 MP3 player (Milpitas, CA, USA), had a 110 dB (A) maximum output when used with earbud style headphones. Due to these high possible outputs, users can potentially listen at levels which are damaging to the ear. Consequently, the study was designed to determine whether PLLs in different types of simulated background noise differ, and how these values vary for different headphone styles. Results demonstrated that with the earbud headphone style listeners have higher PLLs for music as measured in the ear canal during simulated street background noise than when they used an over-the-ear headphone style with or without noise reduction. Under simulated street-noise conditions, this study reported a mean ear canal level of 88.83 dB (A) for subjects using earbud headphones, and determined that the maximum noise dose for this level would be reached within 3.3 hours. Given that Hodgetts et al. reported the highest PLLs for participants wearing earbud headphones in the noisiest environment, it is important to further investigate PLLs for this headphone style in a common noisy environment such as a public transit system. Hodgetts et al. suggested that further research should examine data from both male and female subjects who routinely use PLDs, since not all participants were PLD users. The study was also limited in that results generalization might be appropriate only in situations involving popular music stimuli with a steady level (Hodgetts et al., 2007). While its single stimulus design ensured consistency in musical characteristics across subjects, it failed to imitate the characteristics of the music preferences of a particular subject. As it is possible that listeners would use different PLLs in their typical environments and while listening to their own music, the average acoustical characteristics of an individual’s typical listening choices should be determined by his or her musical taste (Hodges & Barrett, 1995). Other researchers have chosen more than one song to be used as stimuli for their simulated real-ear measurements. Abmed et al. (2007) administered a survey to 150 undergraduates about factors affecting their hearing health and PLD use. Twenty-four of those students surveyed also participated in testing which included conventional and extended high  17 frequency audiometry and iPod output measurements. Participants were asked to adjust a test iPod to their PLL in various simulated environmental listening conditions. Two samples of two different songs, one of a Hip-Hop genre and the other of an Electronica genre were used for the stimuli. Additionally, simulated real-ear measures using a manikin head were conducted using a Bruel and Kjaer sound level meter with a PULSE sound measurement system. Survey results indicated that most undergraduate university students surveyed possess at least one PLD. Audiometric testing produced no evidence of hearing loss. Results showed that for the test iPod PLL measurements the average PLL was at the safe listening volume of 67.6 dB (A), although the value depended primarily on background noise rather than music genre. In the high level traffic noise, the average PLL was 73.3 dB (A). Although it is interesting that this study employed more than one musical genre in its design, it is important to note the possibility that participants who did not enjoy one or both of the two genres may have set the volume at a lower level for the given song(s). Individuals who listen to PLDs regularly might choose different volume settings when listening to music of their choice versus music selected by researchers, even if chosen based on record sale popularity charts. It is possible that a given individual who volunteers for a research session may have musical taste contrary to popular opinion. For instance, Vogel et al. (2008) reported that participants who turned up the volume to high levels on their MP3 players cited a desire to hear a favourite song well as one justification for the volume setting. Hence, it is possible that the results underestimated participants’ actual PLLs for their own musical choices. As previously mentioned, Thiery and Meyer-Bisch (1987) found that the combination of transient noises and continuous noise increases the risk of hearing loss. Because certain listening choices will contain greater numbers of transients, comfortable listening levels for these tracks may result in very high levels of transients. Measuring the PLL for each subject by using an identical musical stimulus may not provide an accurate picture of his or her PLL in everyday  18 circumstances. In addition, results from a single laboratory session may not be representative of a subject’s PLL over time. Finally, there is a lack of research on real-ear measures of PLLs for PLDs including subjects who frequently use these devices. In summary, NIHL as a result of PLD use is likely given the widespread availability of the technology and the lack of safe upper limits. A majority of the above studies indicate that PED use can cause hearing loss, which is more likely in listeners who listen for long durations, particularly in noisy environments with earbud style headphones. Nevertheless, questions remain regarding the characteristics of typical PLD users’ music exposure. Specifically, previous research has not investigated the effects of typical listeners’ everyday environments on their PLLs for their own musical choices. Further, the majority of the studies discussed above did not include actual real-ear measurements in their experimental designs.  1.4  Challenges of a Realistic Experimental Design The investigation of PLD use among typical listeners is best served by a design featuring  the collection of data from real life listening situations. As the above studies illustrate, a realistic approach to the investigation of PLD use is not without its challenges. The following section outlines those challenges most pertinent to the current study. As the PLDs of interest in the current study are MP3 players and iPods, the term PLDs will be used to refer exclusively to these devices from this point forward in the report. First, obtaining realistic objective measurements of PLD output can prove to be a significant challenge. While a coupler or simulated real-ear approach can be more convenient and require less participant time, its use introduces complications. When real-ear-to-coupler differences (RECDs) are employed in combination with HAl 2cc coupler or manikin measurements, results should be more representative of actual levels in a given participant’s ear. However, the reliability of RECD measurements for earbud style headphones has not been  19 determined. For instance, the coupling of earbud headphones to hard walled couplers is complicated by the fact that the headphone receivers are larger than the opening in the coupler. Additionally, researchers have noted that the mounting of earbud headphones in simulated ear canals greatly affects the frequency response and can create earphone-mounting-related measurement errors (Farina, 2007). Finally, hard-walled couplers such as the HAl differ from real ears in that the coupler walls lack acoustic resistance. Ear simulators do imitate the acoustic resistance and frequency response found in a median adult ear canal, but do not capture individual differences in ear canals among adults (Hersh & Johnson, 2003). Hence, the use of actual real-ear measurements is the preferable method to obtain realistic objective PLD output data. Although the inclusion of real-ear measurements is important in a study on PLDs, they cannot be obtained in listeners’ typical environments. Real-ear measurements allow an investigator to obtain data that is representative of a given listener’s unique musical choices and ear canal acoustics, quantifying each participant’s unique frequency response at the eardrum while listening to his or her PLD. The most accurate and comprehensive information about PLD users’ listening habits would be obtained by a dosimeter with a real-ear module. However, such a device neither exists currently nor would be practical for volunteers to wear over an extended period of time in order to obtain stable long term measurements. Since real-ear equipment must be placed by an audiologist, a study that includes real-ear measurements is best done in the laboratory or clinic. A second challenge is that the environments in which PLD users listen to their devices are unique to each individual. Unfortunately, a laboratory cannot replicate the dynamic and unique environment or combination of environments in which a volunteer normally listens to his or her PLD on a regular basis.  20 Third, a distinguishing feature of the PLD is that it gives listeners the ability to keep an individualized music library in a portable device since it can store large numbers of songs and albums. As such it is a challenge to choose one song that most volunteers will likely have in their music library. Ideally an investigation of PLD use should examine data using a variety of music chosen by each listener in order to produce data that is representative of the listening habits of its participants. Vogel et a!. (2008) demonstrated the importance of this when describing that participants who turned up the volume to high levels on their MP3 players cited a desire to hear a favourite song well as one justification for the volume setting. A fourth challenge of a realistic approach to the current topic is that listeners use many different headphone styles and brands with PLDs. Differing headphone styles can influence PLLs in noisy environments (Hodgetts, 2007). Consequently, a variety of headphone styles among participants can confound results unless headphone style is a variable of interest. Nevertheless, some styles are more common than others, as mentioned above. Earbud headphones in particular remain popular (Zogby, 2006) but are made by many different manufacturers. This may add unnecessary variability to the frequency response measurements if participants use headphones made by more than one manufacturer. A fifth challenge is the use of self-report measures, which can be either helpful or a hindrance, depending on the purpose and reliability of the reports. Ahmed et al. (2007) reported differences between participants’ self-reported or subjective volume settings and their objective volume settings. Specifically, most participants’ self-reports indicated that they set the volume of their devices above halfway on the volume meter. However, objective measurements showed that this was the case only for environments with high noise, and that in fact greater numbers of participants set the volume lower than halfway for environments with low noise (Ahmed et a!., 2007).  21 1.5  Summary ofthe Current Study’s Experimental Design and Goals In an effort to overcome a number of limitations seen in previous studies as described  above, the current study addressed these five challenges in a unique design. The design included real-ear measurements, individual volume setting data from a listening log completed by each participant in their typical listening environments, and music samples chosen by each participant. Participants used their own PLDs with standard iPod earbud headphones if owned, or were provided with earbud headphones. The study used two self-report measures. The first was a questionnaire, which was intended as both a piloting tool for future studies and a means to gather information about participants’ noise exposure history, knowledge and attitudes regarding music exposure and hearing loss. The second was a listening log, which required participants to record objective volume setting information over a two-week period. The use of data from the two-week listening log enabled the calculation of a stable average of volume settings in different everyday environments, which were subsequently used for the real-ear measurements. The hearing screening and real-ear measurement procedures used in the current study are similar to those used in the experiment by Hodgetts et al. (2007), for replication purposes. Participants included male and female typical PLD users with normal hearing who commute to school or work on public transit. It was important to recruit participants who normally listened to their PLDs on public transit in order to ensure that all participants had a regular noisy listening environment. The overall aim for the current study was to determine whether the decibels (dB) of the PLLs for PLDs, as set by typical users in their daily acoustic environments, were sufficiently high to damage hearing. We predicted that PLLs in noisy environments, specifically in average Metro-Vancouver transit environments, would be dangerously high for some individuals.  22 PLD users have shown interest in learning whether or not their listening habits endanger their hearing health, as evidenced by the fact that previous studies have recruited participants on this topic (Hodgetts et al., 2007; Torre, 2008). This study is unique in that it provided individual listeners with measured information about their real-life listening habits. In the event that such information might change previously unsafe listening habits to safe habits, this information could be beneficial to participants’ hearing health. The real-ear sessions of the study may have served as a counselling tool for any such participants, since the participants could both see the real-ear levels on the Fonix display and hear for themselves how loud their PLLs for noisy environments seem in a quiet laboratory. In summary, because previous research has shown that maximum ear canal levels corresponding to PLLs in simulated background noise are alarmingly high with earbud headphones (Hodgetts et al., 2007) it is a logical and necessary step to determine the maximum ear canal levels corresponding to PLLs in typical background noise situations with this headphone style. Investigating this step will allow greater generalization of the results to real world listening conditions. Increasing public awareness of the potential for hearing loss among typical PED users could promote the adoption of guidelines to ensure a safe daily noise dose for consumers of recreational music.  23 Chapter 2: Methods 2.1  Participants Participants were 7 male (age range 22-44; mean 28.86 years) and 6 female (age range  15-25; mean 20.00 years) PLD users recruited from high schools, universities, and community settings in Vancouver, British Columbia. Eleven participants had or were currently obtaining a university education, while 2 participants were currently obtaining a high school education. The following inclusion criteria were used: (a) subjects must be PLD users who use the device l hour per day; (b) subjects must be high school students or adults who commute on public transit; (c) subjects must have pure tone thresholds better than 20 dB HL at conventional frequencies with an air-bone gap of10 dB; and (d) subjects must have a normal 226 Hz probe tone tympanogram and present ipsilateral broad-band-noise-elicited acoustic reflexes. To ensure that daily listening log data were collected in a consistently noisy environment it was important that subjects either use or work on public transit. There was a high participant attrition rate for this experiment (24%). Four out of seventeen initial participants tested dropped out of the study after the first session was completed.  2.2  Equipment The Grason-Stadler Instruments (GSI) 61 audiometer was used to screen participants’  hearing. The tympanometer used for tympanometry and reflex testing was the GSI Tympstar with Version 2 software. Each participant used his/her own PLD for the experiment. The devices used included 8 iPods, 3 Creative MP3 players, 1 Rio MP3 player and 1 Sony MP3 player. iPods have a volume limiting option which the user can enable in order to limit the maximum usable volume on the  24 device. All participants with iPods reported that they were not using the volume limiting option if they were even aware that the device had the option. To generate the stimuli for measurement, each subject was asked to choose from his/her PLD three songs considered representative of the music genres to which he/she normally listened. Given that this study aimed to produce data that are representative of real-life listening experiences, differences in acoustical characteristics among genres were accounted for in the measurements. Using three different stimuli for each subject permitted a better picture of a given subject’s musical exposure, and may have provided overall measurements that better represented the typical PLLs for that subject. Earbud headphones (Panasonic RP-HV260/266) were supplied to 7 out of 13 participants, which were used during the two weeks in which they completed the listening log and during the real-ear measurements in the lab. This was done to minimize differences in PLLs due to headphone style and to maintain consistency across subjects. Three of six participants not using these headphones were using iPod stock headphones. Due to the fact that iPods and some MP3 players display no numerical volume setting indication, participants who used iPods or MP3 players without numerical volume indication were given a ‘volume ruler.’ This was simply a 1 to 10 label participants could place on their iPods or MP3 players adjacent to the area of the screen where the volume bar was located. The ‘volume ruler’ made it possible for these participants to objectively and consistently determine their volume settings during their listening log period. Participants were provided with two forms to fill out during the 2 week period after the hearing assessment. The first was the listening log, which required participants to record their volume setting information over a two week period in three different listening environments (quiet, moderate, and public transit). A copy of the listening log form can be found in Appendix B. The second was the questionnaire, which contained questions regarding participants’ noise  25 exposure history, knowledge and attitudes regarding music exposure and hearing loss. A copy of the questionnaire can be found in Appendix C. The musical genre of participants’ musical samples was determined by entering the music sample title and artist name into the search function in the Apple iTunes Store, Version 7.6.1.9 (Apple Inc., 2000-2008). This was done in order to assign genre to music samples objectively. In cases where a music sample could not be found in iTunes, the participants’ genre categorization was used. The Fonix 7000 real ear system (Frye Electronics, Tigard, U.S.A.) was used to perform real-ear measurements on all subjects. The Fonix 7000 software included the real-ear option. This study used the Visible Speech screen, which is found within the real ear option. Using Visible Speech, real-ear measurements were made using participants’ PLDs as external sources. The Fonix 7000 was attached to a personal computer equipped with WinChap software, which is software that enabled the researcher to transfer the real-ear data from the Fomx 7000 to the computer where it could be stored and copied into spreadsheets. For the real-ear measurements, Fonix hardware including a probe microphone with a detachable earhook was used. The probe microphone was plugged into a remote real-ear module, which was placed on a remote module shelf attached to a floor stand. Fonix probe tubes were used with the probe microphone, and medical tape was also used to secure the probe tubes in the participants’ ears. PLLs for each environment were measured with the Fonix 7000 real ear system for a 30-second sample of the subject’s chosen stimuli set at his or her PLLs. Within the visible speech menu, the following settings were made: a) Noise Reduction 16x; b) Smoothing off; c) Mm/Max On.  2.3  Procedure The procedures used in the current study are similar to those used in the experiment by  Hodgetts et al. (2007) for replication purposes. Participants were asked to come to the clinic for  26 testing on two separate sessions. During the first session to confirm normal hearing status subjects were given an audiological assessment that included otoscopy; pure-tone air and boneconduction audiometry at conventional frequencies (i.e., 250-8000 Hz); 226 Hz probe tone tympanometry; and broad-band noise elicited ipsilateral acoustic reflex testing. Subjects were required to meet the criteria for inclusion in the study. Unlike the study by Hodgetts et al., the current study included immittance, middle-ear-muscle reflex and bone-conduction testing in the audiological assessment in order to screen out conductive, neurological, and synchronization abnormalities. Hearing losses of any type will likely result in the use of higher PLLs. Thus, efforts were made to ensure that all subjects had no audiological impairments. Also during the first session, all participants were reimbursed a total of $10 for their time, provided with the listening log form and the questionnaire and given orientation to completing these forms. Additionally, those participants using an iPod or an MP3 player without numerical volume indication were given a ‘volume ruler.’ Participants were asked to keep a log of their average preferred listening volumes, including estimates of duration of listening at these volumes, in three common listening environments corresponding to quiet, moderately noisy and noisy surroundings (e.g., library, cafeteria/coffee shop, and public transit). Subjects were asked to record the fraction of the maximum volume at which they were listening to the device: e.g., 4/10 of the maximum volume. In each of the three environments, subjects recorded their PLLs every day for a total of two weeks. An average value was recorded if numerous volume adjustments were made in one session in a given environment. The participant questionnaire asked questions regarding knowledge of, and attitudes toward various topics, such as hearing protection, loud music, PLDs, etc. Data obtained from these questionnaires were used to assess potential for further studies concerning knowledge and attitudes toward these topics.  27 At the second session, real-ear measures of the participants’ PLLs were made in a quiet room with an average noise floor of 48.88 dB (A). For one participant’s test session the noise floor reached an average of 57.063 dB (A), although the levels measured in the participant’s ear were 20 dB or more above the noise floor at all times. The real-ear measures employed in this study are common clinical procedures which carry low risk of discomfort or irritation. The reason for measuring PLLs in the ear canal as opposed to measuring them in an external device such as the coupler is due to the unique resonances of each individual’s ear canals. The coupler is the size of an average adult’s ear canal; thus, it does not account for individual differences in the size and shape of the ear canal, nor does it approximate the volume of an individual’s ear canal when an earbud headphone is inserted. As such, PLL measurements made in the coupler will not be as accurate as measurements made in the real ear at determining the SPL at the eardrum for a given subject. A probe tube was inserted into the ear canal within 5 mm of, but not touching, the eardrum (Audioscan, 2005). Measurements taken within 6 mm of the eardrum give the most accurate estimate of the sound pressure level at the eardrum (Dillon, 2001). To ensure proper insertion depth probe tubes were marked 30 mm from the tip for males and 28 mm for females (Audioscan, 2005). Upon insertion, this mark was aligned with the inter-tragal notch. Proper placement of each probe tube was verified via otoscopy; the probe tube was then held in place with a piece of tape placed immediately below the inter-tragal notch (Hodgetts Ct al., 2007). The earbud headphones were then placed in the subject’s ear, on top of the probe tube. Measurements were taken in the left ear unless wax precluded probe tube insertion. For each stimulus, measurements were taken at 1 minute and 30 seconds into the song, and the participant’s MP3 player was started before pressing start on the Fonix 7000. The time of 1:30 was chosen in order to bypass introductions, which when present in music are often of a different (usually quieter) intensity and style from the rest of the piece. The real-ear system was used to  28 analyze the level and frequency content of the three stimuli at the eardrum. Real-ear measurements of the maximum and long-term average music spectra (ETAMS) were made for each subject, at the preferred listening volume used for each listening environment for all three stimuli. Moreover, spectral analysis of the ear canal output was conducted to analyze individual SPL at each frequency between 200-8,000 Hz at 100 Hz or larger intervals. The overall SPL was obtained by adding individual SPLs using equation 1. The dB (A) was also calculated at each individual frequency using equation 2 and the overall dB (A) was obtained using equation 1.  N  Equation 1:  L P =lOLog  L,  1O’° dB i=1  Where L is the total SPL in dB generated by N sources and L 1 represents the individual SPLs to be added (ANSI S1.4-1983; ANSI S1.42-2001).  Equation 2.  122002. f4  =  RA(f)  2 + 20.69 (f A  =  V’(f2  + 107.72)  2 + 737.92) (P + 122002) (f  2.0 + 20 log. 10 (RA(f))  Where RA(±) is the overall dB(A) value for a given frequency, ± (ANSI Si .4-1983; ANSI S 1.42-2001).  The mean dB (A) levels for each environment were obtained by taking the average across each participant’s 3 stimuli. Total time in each environment was calculated as the mean duration in a given environment per listening day. Total duration in each environment was thus divided  29 by the number of days for which the participant entered information in the listening log, which was less than 14 days in some cases.  2.4  Data Analysis Procedure Daily noise exposure associated with PLD use for each participant was calculated using  the following formula: Dose  100 x T/8 x l0(Leq-85)/10 %  Where Dose is a noise exposure dose expressed as a percentage and acquired in T hours, Leq  5  the dB (A) weighted, sound level linearly energy averaged over T hours, and T is the sampling time of the measurement expressed in hours (Worksafe BC, 2007). Leq was calculated as a dB (A) weighted measure of SPL at the eardrum for each listener, averaged across stimuli. Each participant’s overall Time Weighted Average Noise (TWAN) dose was calculated using the participants’ average dB (A) values obtained for each environment as well as the reported average listening durations in each environment. In this report, the TWAN refers to the average level of the music sample during the 30 second measurement. Hence the TWAN dose is the percentage of the permissible amount of daily noise exposure that an individual has obtained. As stated above, this report defines 85 dB (A) for 8 hours as the maximum permissible amount of noise exposure, equal to a TWAN dose of 100%. The following calculation determined each participant’s Time Weighted Average Noise (TWAN) dose: TWAN  T/Ta + T/Ta + T/Ta  Where (T) is defmed as above, and Ta is the number of actual minutes of exposure for a given listening condition. Values of 1.0 denote a TWAN dose of 100%. For example, looking at Table 3 in the Results section below, participant iPod 010 has an overall TWAN for average curves of 0.11. This value means that the participant was obtaining 11% of their daily noise dose  30 from PLD use alone. From these calculations we determined how many subjects were exceeding the maximum daily noise dose. A number of statistical analyses were used to analyze the data. First, a repeated measures ANOVA having one independent variable, environment, with three levels (quiet, moderately noisy and noisy), and one dependent variable, volume setting, was performed. Second, a 2 x 2 x 3 mixed model ANOVA was performed. The three independent variables were gender, with two between-subjects levels (male and female), frequency weighting, with two repeated measures levels (dB (A) and linear), and environment, with three repeated measures levels (quiet, moderately noisy and noisy). The dependent variable was dB SPL. The ANOVA also analyzed the data to determine any interactions between the independent variables. Third, a 2 x 3 x 44 mixed model ANOVA was conducted to analyze the data. The three independent variables included gender, with two between-subjects levels (male and female), environment, with three repeated measures levels (quiet, moderately noisy and noisy) and frequency, with 44 repeated measures levels (44 frequencies 200-8000 at irregular intervals). This ANOVA also analyzed the data to detennine any interactions between the independent variables. The dependent variable was un-weighted dB SPL. It was expected that PLL and volume setting would increase with noise in the listening environment. There were no predicted effects of gender or genre. The statistical analyses included in this study were performed using Statistica, Version 6.1 (Statsoft Inc., 2003).  31 Chapter 3: Results 3.1  Descriptive Results Questionnaire forms were completed and returned by all participants. Responses to  selected questions can be found in Table 3.1. These questions were selected in favour of others that had no variation in response across participants, had long responses or had vague responses that added little information to the study. A number of the selected questions asked participants to consider their attitudes towards hearing protection. For one such question, 9 of 13 participants said it was ‘very important’ to protect their hearing, and 4 participants said it was ‘important.’ For another such question, 6 of 13 participants reported that they were ‘very likely’ or ‘likely’ to wear clear or flesh coloured earplugs at a concert. On average, participants did not report long PLD listening durations on a typical listening day in their listening logs. Average listening durations per listening day ranged from 18 to 168 minutes. Although participants were recruited on the basis that they typically listened to their PLDs an hour or more per day, the data gathered during the study revealed that 3 of the 13 participants did not do so. The real-ear data of interest were the average and maximum (peak) curves from each of the 9 measurements per participant. Thus a total of 18 curves were examined for each participant. Values for dB (A), total time in minutes (T) per day of permissible exposure at that level, total time in minutes (Ta) per day of actual exposure (average), and Time Weighted Average Noise Dose (TWAN) are listed for quiet, moderately noisy, and noisy environments in Table 3.2. In general, the dB (A) values corresponding to participants’ PLLs were conservative. To illustrate, even in noisy environments only 3 of 13 participants reached or exceeded 80 dB (A) for average curves.  32 The TWAN dose per day for each participant, which takes all listening environments into account, is listed for both minimum and maximum (peak) curves in Table 3.3. These calculations used the mean dB (A) values for each environment with the mean listening durations in each environment for each participant. Where the TWAN dose exceeded 1.0, the participant was exceeding the standard permissible amount of daily noise exposure. Any such participant was advised to reduce his or her noise exposure by reducing the volume, listening duration, or both, and also to use hearing protective devices in noisy situations when they are not wearing headphones. Based on maximum (peak) curves, only one participant was exceeding the standard permissible amount of daily noise exposure. Based on average curves, no participants were exceeding the standard permissible amount of daily noise exposure. Table 3.4 lists the number of song samples per musical genre, per male, female, and all participants. Four of the song samples listed under the genre ‘Pop’ are non-English-language popular music selections. The genre ‘Podcast’ describes an audio broadcast that listeners can subscribe to over the internet and download to a computer and or PLD. The podcast samples used in this study are podcasts of television programs. It can be seen that the largest number of samples was from the Pop genre, and the second largest from the Rock genre. Table 3.5 lists the average dB (A) and dB SPL (linear) values in each environment for the 4 most common musical genres sampled in this study, namely Pop, Rock, Independent Rock/Alternative and Hip-Hop/Rap. Note that the highest dB (A) or dB SPL (linear) values were obtained for samples of Independent Rock/Alternative music. Table 3.6 lists participants’ average volume settings in each environment, and average volume settings collapsed across environments. The volume settings are expressed as percentages of the total possible volume. Note that 8 of the 13 participants’ average volume settings, when collapsed across environments, were less than 50%. This indicates that the majority of participants chose conservative volume settings.  33 3.2  Statistical Results The first analysis, which was the repeated measures ANOVA for volume setting across  the three environments, revealed that participants’ average volume settings differed significantly , 22) 2 between quiet, moderately noisy and noisy environments (F(  12.27, p <0.05). A graph of  this difference is given in Figure 3.1. It should be noted that the high variation in confidence intervals in all statistical results may be due to the small sample size in this study. Large error bars can be seen in Figures 3.1—3.3. However, the differences shown in these figures are small yet statistically significant. For the first analysis, results showed that volume setting increased by approximately 10% in moderately noisy versus quiet environments as well as in noisy versus moderately noisy environments. The second analysis, which was a mixed model ANOVA, examined the effects of gender, linear versus dB (A) frequency weighting and environment. This analysis revealed no significant effects of gender (F(l, 11) = 0.7, p  >  0.05). However, significant effects were seen for linear  versus dB (A) frequency weighting (F(l, 11)  =  8.22, p <0.05) and for environment (F( , 22) 2  12.79,  p <0.05). The effects of environment on level, regardless of frequency weighting, replicated the effects of environment on volume setting in that both level and volume setting increased from quiet to moderately noisy to noisy environments. There were no interactions. The significant differences are illustrated in Figure 3.2 for the difference between dB (A) and linear frequency weighting for overall level in dB SPL, and in Figure 3.3 for the average levels in dB SPL in different environments, respectively. The third and final analysis, which was another mixed model ANOVA, examined the data for any variations in dB SPL (non-weighted/linear) across frequency bands related to gender or environment. There were no significant effects of gender (F(l,  11)  =  0.07, p> 0.05), while there  were significant effects of environment (F( , 22) = 15.45, p <0.05) and frequency (F( 2 , 473) = 43 14.40, p <0.05). Additionally, there was an interaction between environment and frequency  34 , 946) 86 (F(  =  10.54, p <0.05) indicating that the variation of the energy in dB SPL across  frequency is significantly different between different environments. A Greenhouse-Geisser epsilon correction showed that these results remained significant after the correction was performed. The variations of energy in dB SPL across frequencies for different environments are shown in Figure 3.4. In order to investigate the frequencies at which the group differences occurred, a post-hoc Tukey Honestly Significantly Different (HSD) test was performed. The post hoc Tukey HSD test revealed significantly higher dB SPL values between 200 and 4000 Hz in moderately noisy environments in comparison to quiet environments. Significantly higher dB SPL values were found between 200—5600 Hz in noisy environments in comparison to moderately noisy environments. Similarly, significantly higher dB SPL values were found between 200—6300 Hz in noisy environments in comparison to quiet environments. Essentially, the dB SPL in the high frequency region did not change significantly from one environment to the other, whereas the dB SPL in the low to middle frequency region did change significantly. Genre was not analyzed statistically in this study because the small number of samples for some of the genres meant that effect sizes would be too small to be detected. However, data were visually examined for genre-related variations in energy across frequencies, in different environments. These relationships are depicted in Figures 3.5, 3.6 and 3.7. Each genre had a unique spectrum. For instance, it can be seen that in quiet environments, the genre Independent Rock/Alternative had more energy around 200, 2500 and 4700 Hz in comparison to the other genres. This difference was increasingly enhanced for moderately noisy and noisy environments.  35 Table 3.1 Selected Questionnaire Responses  n  n  n  (males) (females) (adults)  n  %  (teens)  N  How likely would you be to do the following at a concert/club? Wear clear/flesh coloured earplugs? Very likely  2  1  3  Likely  1  2  2  Somewhat likely  1  Not likely  3  3  5  1  46.15  Very likely  4  3  6  1  53.85  Likely  2  2  4  Somewhat likely  1  1  1  Very likely  1  1  2  Likely  1  2  1  Somewhat likely  3  2  5  38.46  Not likely  2  1  3  23.08  4  30.77  23.08 1  1  23.08 7.69  Situate yourself away from speakers?  30.77 1  15.38  Not likely Stay for a limited amount of time?  Have you ever worn earplugs at a concert, etc.? -Yes  4  15.38 2  23.08  36 n (males) Have you ever experienced ringing in your ears  7  n  n  n  (females) (adults) (teens) 2  % N 100.00  6  11  2  2  15.38  after attending a noisy event? Yes -  How often do you attend concerts? More than once a week Between once a week and once a month Once every couple of months  2  1  3  23.08  Once or twice a year  4  1  5  38.46  Never  1  2  1  2  23.08  Less than two years  1  1  1  1  15.38  Between two and four years  4  3  6  1  53.85  Five years or more  2  2  4  iPod  4  4  6  Creative  1  2  3  23.08  Rio  1  1  7.69  Sony  1  1  7.69  How long have you been using an MP3 player or iPod?  30.77  What brand of MP3 player do you use? 2  61.54  How often have you used a personal listening device such as a Walkman or CD player with headphones, other than an MP3 player? Very often  1  1  1  1  15.38  37 n  II  fl  n  (males) (females) (adults) (teens)  % N  Often  1  1  7.69  Someone often  1  1  7.69  Not often  2  4  5  Never  2  1  3  23.08  3  23.08  69.23  Have you ever worked in a noisy environment?  3  1  46.15  -Yes How important do you feel it is to protect your hearing? Very important  6  3  9  Important  1  3  2  Somewhat important Not important  2  30.77  Table 3.2  dB(A) Levels for Quiet, Moderately Noisy and Noisy Environments, averaged across each Participant’s 3 Stimuli, Total Time in  minutes (7’) per day ofPermissible Exposure at that Level, Total Time in minutes (Ta) per day ofActual Exposure (average), and  Moderate  Quiet  Noisy  Moderate  Quiet  72.55  72.55  72.55  77.99  67.78  59.03  dB(A)  368223.95  8521.49  8521.49  8521.49  2424.64  25653.90  193712.46  T  60.00  70.45  97.78  97.78  97.78  34.64  41.79  16.21  Ta  0.00  0.00  0.00  0.01  0.01  0.01  0.01  0.00  0.00  TWAN  73.39  66.45  65.41  77.53  77.53  77.53  83.03  71.82  73.47  dB(A)  7018.23  34882.70  44357.50  2696.53  2696.53  2696.53  756.69  10087.10  6889.69  37.73  60.00  70.45  97.78  97.78  97.78  34.64  41.79  16.21  Ta  0.01  0.00  0.00  0.04  0.04  0.04  0.05  0.00  0.00  TWAN  Maximum (Peak) Curves  Noisy  56.25  143453.53  37.73  Average Curves  Quiet  60.33  31005.23  T  Moderate  66.96  Time Weighted Average Noise dose (TWAN)  Participant iPod 001  iPod 002*  iPod 003  Noisy  38  Participant iPod 004**  iPodOO5***  iPodOO6  iPod 007  iPod 010  Average Curves  Moderate  Quiet  Noisy  Moderate  Quiet  Noisy  Moderate  Noisy  Moderate  Quiet  75.75  75.12  76.30  63.13  57.43  53.24  89.78  86.81  90.51  90.51  86.27  322.59  4068.34  4705.80  3582.85  75119.02  280354.09  738151.42  159.07  315.95  134.38  134.38  57.94  16.11  2.40  45.71  4.29  4.29  31.40  40.40  20.70  42.29  16.07  61.67  61.67  30.41  Ta  0.10  0.01  0.01  0.01  0.00  0.00  0.00  0.00  0.00  0.31  0.05  0.46  0.46  0.09  TWAN  93.53  85.54  91.71  81.47  81.21  84.36  67.07  63.59  61.43  93.62  91.54  94.27  94.27  91.79  dB(A)  66.88  423.70  101.84  1085.06  1152.24  556.49  30227.15  67544.81  111258.59  65.51  105.92  56.37  56.37  99.98  T  16.89  16.11  2.40  45.71  4.29  4.29  31.40  40.40  20.70  42.29  16.07  61.67  61.67  30.41  Ta  0.25  0.04  0.02  0.04  0.00  0.01  0.00  0.00  0.00  0.75  0.15  1.09  1.09  0.30  TWAN  Maximum (Peak) Curves  Noisy  86.72  1920.00  16.89  T  Quiet  79.00  172.87  dB(A)  Moderate  89.42  Quiet  Noisy  39  Participant iPod 013  iPod 014  iPod 015  iPod 016  iPod 017  Quiet  Noisy  Moderate  Quiet  Noisy  Moderate  Quiet  Noisy  Moderate  Quiet  Noisy  Moderate  Quiet  65.45  58.20  66.16  56.27  50.77  56.42  57.83  55.56  75.99  69.72  59.04  56.12  51.68  51.17  dB(A)  3866.71  43949.44  234661.87  37300.07  366526.32  1306151.30  354041.08  255605.13  431865.91  3848.88  16386.54  193131.50  379451.84  1058476.10  1190847.52  T  27.50  13.57  67.86  2.73  4.09  11.64  36.60  25.80  83.40  64.00  11.73  30.91  65.71  19.29  34.29  Ta  0.01  0.00  0.00  0.00  0.00  0.00  0.00  0.00  0.00  0.02  0.00  0.00  0.00  0.00  0.00  TWAN  83.65  70.85  63.33  72.11  60.61  54.16  61.51  58.78  60.85  82.68  76.77  71.57  60.23  54.45  56.64  dB(A)  655.70  12621.16  71726.76  9433.37  134466.81  596801.07  109220.99  205231.21  127213.35  820.42  3214.16  10686.91  146806.60  558123.14  336494.62  T  27.50  13.57  67.86  2.73  4.09  11.64  36.60  25.80  83.40  64.00  11.73  30.91  65.71  19.29  34.29  Ta  0.04  0.00  0.00  0.00  0.00  0.00  0.00  0.00  0.00  0.08  0.00  0.00  0.00  0.00  0.00  TWAN  Maximum (Peak) Curves  Moderate  75.97  Average Curves  Noisy  *Values are the same for all environments  40  *No listening in quiet environments  **Values are the same for both moderate and noisy environments **  41  42 Table 3.3 TWAN Dose per day, accountingfor Participants Preferred Listening Level (PLL) and ‘  Listening Duration in each Environment, for Average Curves and Maximum (Peak) Curves  TWAN Participant  Average Curves  Maximum (Peak) Curves  iPod 001  0.02  0.05  iPod 002*  0.01  0.04  iPod 003  0.00  0.01  iPodOO4**  0.54  1.40  iPodOO5***  0.32  0.80  iPod 006  0.00  0.00  iPod 007  0.01  0.05  iPodOlO  0.11  0.31  iPod 013  0.00  0.00  iPod 014  0.02  0.09  iPod 015  0.00  0.00  iPod 016  0.00  0.00  iPod 017  0.01  0.04  * Values  are the same for all environments  **Values are the same for both moderate and noisy environments * * *No  listening in quiet environments  43 Table 3.4 Number ofSong Samples per Musical Genre, listedper Male, Female, and Male and Female Participants  Number of Song Samples Genre  Male Participants  R&B/Soul  Female  Male and Female  Participants  Participants  2  2  Hip Hop/Rap  2  1  3  Pop  4  8  12  1  1  Classical Rock  4  3  7  Independent  3  1  5  1  1  2  Rock/Alternative Comedy Talkshow Podcast/TV & Film Podcast Country  2  Balkan Brass Band  2 1  1  World  3  3  Modern  1  1  Instrumental Ensemble  44 Table 3.5 Average dB (A) and dB SPL (Linear) per Genre in Quiet, Moderately Noisy and Noisy Environments, for the 4 Most Common Musical Genres from Music Sampled in this Study  Average Curves Genre  Number of  dB (A)  dB SPL (linear)  Samples Quiet  Moderately  Noisy  Quiet  Noisy  Moderately  Noisy  Noisy  Pop  12  61.06  64.09  68.59  61.76  64.76  69.25  Rock  7  67.42  74.37  78.32  67.77  74.63  78.53  md. Rock!  4  72.13  79.79  85.23  72.83  79.81  85.32  3  67.82  67.70  75.19  68.65  68.54  76.09  Alternative. HipHop/Rap  45 Table 3.6 Average Volume Setting  (%) in D(ferent Environments  Average Volume Setting Participant  (%)  Quiet  Moderately  Noisy  All  Environments  Noisy  Environments  Environments  Environments iPod 001  38.00  56.00  71.20  55.07  iPodOO2*  4.00  4.00  4.00  4.00  iPod 003  30.50  44.20  56.40  43.69  iPodOO4**  86.75  100.00  97.75  94.83  45.28  49.20  47.24  iPod 005***  *  iPod 006  31.50  48.50  44.00  41.33  iPod 007  66.00  64.00  65.20  65.07  iPod 010  81.20  64.00  83.30  76.17  iPod 013  8.00  14.00  36.60  19.53  iPod 014  21.20  57.00  67.04  48.41  iPod 015  36.10  38.00  40.00  38.03  iPod 016  16.70  40.75  60.70  39.38  iPod 017  43.50  61.38  88.00  64.29  Values are the same for all environments  **Values are the same for both moderate and noisy environments ***No listening in quiet environments  46 Figure 3.1 Percentage ofthe Maximum Volume Setting usedfor Volume Settings in Quiet, Moderate and Noisy Environments  Current eflect F(2, 22)=12.271, p=.00026 Vercat bars denote 0.95 confidencet ntervals  90 80 70 60 50 40  cL2O  10  Quiet  Moderate Volume Settings in Diferent Erwironments  Noisy  47 Figure 3.2  Dfference between dB (A) and Linear Frequency Weightingfor Overall Level in dB SPL  :Currentsff9tF(1 12)$06OS. pO 1086 ‘rtica bars denote OJS confidence ntervab 85  80 75  10 6S  60 55  50  AWeighting  Linear  48  Figure 3.3 Average PLLsfor all Sampled Songs in dB SPL in Quiet, Moderate and Noisy Environments  Current efféctF(2.24)13098, p00014 ‘rtical bars denote 096 confidence intervals 90 85  10”  .  —  .,.  60  —-  -  —————-—  55 50  .  de rate Average Levels n Different Enironments  .  Noisy  .—.  49 Figure 3.4 The Effects ofEnvironment and Frequency on dB SPL for Frequencies from 200 to 8000 Hz  .znn(1  .a----  —  —Ezzs  EEzEE!J L0  —  30.00  20.00  10.00  0.00  100  1000 Frequency  10000 -  Hz  —  Noisy Moderately Noisy Quiet  0  -u 0 ‘P  I  0  DC  CD  0  0  0  ‘P  0  I  I  DC  DC  N  ‘I  0 0 0 0  0  0 0  dBSPL  C 0  0  0  C)  C 0 C)  c..)  -  N  00  C-D  C  C  cJ  0  -o  0.  0 C,  I 0  1?  0.  11  N  8C  0 0 0 0  0  -  0 0  dB SPL  oz  0 0. 0  G) o  C 0  I  Co  •a  —.  -  z  0  CD  0. CD  x N  0 0 0 0  0 0  0  0  z  0  0  ‘1  z  2C  0 CD  0  z  I 0  I  DC 0 DC  0 0  dBSPL  ‘II  Qo  53 Chapter 5: Discussion The prevalence of PLD use alerts us to the important role that the hearing health care community plays in assessing typical PLD use and developing appropriate recommendations for listeners and manufacturers. The results of the current study make up a realistic portion of the assessment to date. In the first section of this chapter the results of the current study will be discussed. In the second section these findings will be contrasted with the findings of previous studies. In the third section limitations of the current study will be discussed. In the fourth section the implications of the current study and directions for further research will be explored.  5.1  Discussion of the Current Study’s Results The results of the current study indicate that the majority of participants exhibited  cautious PLD listening habits. Additionally, results from the questionnaire indicated that most participants held cautious attitudes towards noise exposure. It is our impression that this may be partly due to the fact that only 2 of the 13 participants were high school students, since younger individuals are more likely to listen to MP3 players or iPods at higher volumes (Vogel, 2007). Most participants were not exceeding their noise dose for average curves or maximum (peak) curves for their average listening durations per day. Only 1 of the 13 participants (7.69%) was receiving an unsafe noise dose from PLD use for maximum (peak) curves. Only 3 of the 13 participants (23.00%) were receiving 10% or more of their daily noise dose from PLD use alone. As mentioned above, these noise doses were calculated using dB (A) values. Implications of the use of the dB (A) weighting method will be discussed below. The hypothesis that PLL would increase with noise in the listening environment was supported by the results. Participants’ daily listening environments impacted their PLD use in a systematic manner. Both volume setting and real-ear levels significantly increased in increasingly noisy environments. Volume setting increased by approximately 10%, and real-ear  54 levels increased by approximately 10 dB SPL when comparing quiet to moderately severe, and moderately severe to noisy environments. Thus, it can be said that listeners display both significantly higher volume settings and PLLs in noisier environments. One of our initial hypotheses was not supported by the results. We initially hypothesized that the average listening volumes some subjects chose in real life noisy situations, when combined with their average listening durations in these environments would be of sufficient levels to damage the ear. Specifically, we predicted that the Time Weighted Average Noise (TWAN) dose would be exceeded by some subjects, due in large part to PLLs in noisy environments. This prediction was not supported by the results for average dB (A) values, as no participants were exceeding the noise dose for average curves in any environment. However, in one exception the prediction was supported by the results, as 1 participant was exceeding the noise dose for maximum (peak) curves in noisy environments. It should be noted that the results for average curves give a more accurate overall picture of participants’ typical PLLs than maximum (peak) curves. Nevertheless, the result that one participant had a noise dose of 1.40 or 140% for maximum (peak) curves is a signal that he or she is potentially at risk for exceeding the daily recommended noise dose. As the sample size is small this 1 person constitutes roughly 10% of the sample. Given that the percentage of university students who report owning a PLD is approximately 77 % (Ahmed et al., 2007), 77% of the total UBC Vancouver population of 40, 000 students would translate to approximately 30800 students owning a PLD. Consequently, if 10% of these students are potentially exceeding their daily noise dose, this translates to 3080 students who are at risk for preventable hearing loss. Because participants in the current study generally exhibited more conservative PLD listening behaviours than expected, it is possible that the actual number of students at risk on the UBC Vancouver campus is even higher than this estimation.  55 The reason for the lack of significant effects for gender in any of the statistical analyses is not clear, although one reason might be the large difference in mean age between the gender groups. Specifically, the two youngest participants were female and both 15 years old, while the two oldest participants were male and 31 and 44 years old respectively. Consequently, the mean age for males was 8.86 years older than for females, which may have influenced results. Gender effects have been found in previous studies. For example, both Torre (2008) and Ahmed et al. (2007) found differences in volume settings between males and females in the survey components of their studies, both of which had larger sample sizes than the current study. Torre also found gender differences for the real-ear levels corresponding to participants’ PLLs. Specifically, the above gender differences in the two cited studies showed that males preferred the highest listening volumes when compared to females. Therefore, one may speculate that similar gender effects might have been found if the sample size were larger, the mean ages more similar, or if participants were not volunteers but instead randomly sampled. The small yet significant effects found for linear versus dB (A) frequency weighting are due to the fact that higher levels resulted when linear versus dB (A) weighting was used, as can be seen in Figure 3.2. Linear weighting resulted in levels approximately 1 dB higher than dB (A) weighting for the music sampled. Although this difference was very small it could be potentially important in future studies to investigate the impact such a difference makes in noise calculations. When looking at the average spectrum of all music samples in Figure 3.4 it is apparent that overall, participants’ music samples contained the greatest amount of energy in the low frequencies. The dB (A) frequency weighting curve attenuates energy in both the lowest and highest frequency ranges. Consequently, use of this weighting system for the music chosen by participants in this study resulted in slight underestimation of participants’ PLLs and noise doses. In the current study the use of a linear instead of a dB (A) frequency weighting system in the TWAN dose calculations would not have impacted participants’ TWAN doses to the point of  56 altering noise doses from safe to dangerous values. However, with a larger sample and higher volume settings among participants, a linear frequency weighting system could potentially make a difference. Nevertheless, dB (A) frequency weighting was used in this study in order to assess participants’ PLLs using current recommended occupational noise exposure limits, and in order to facilitate comparison of results to previous studies. If the music chosen by participants in this study is representative of that typically chosen in the general population, then it follows that the dB (A) weighting system may likewise underestimate the noise dose of a typical PLD user. However, the significant effect found for linear versus dB (A) frequency weighting is too small to hold any practical significance in terms of noise exposure calculations in the field. Further research should be conducted to determine the magnitude of the difference using a larger sample size and a greater selection of music samples. The current study’s finding that variation in the distribution of energy at each frequency for different environments provides one reason why the entire frequency spectrum should be examined in studies relating to music exposure. This is because the dB SPL in the low to middle frequency region increased significantly when comparing results for quiet and moderately noisy environments, and further increased for comparisons between moderately noisy and noisy environments. The reason for this nonlinear change in frequency spectrum with increased volume is not known, although it likely is related to the function of the PLDs or earphones. It is possible that participants’ PLLs would be different for different environments if the frequency response did not change with increasing volume. For instance, if levels in the high frequencies increased at the same rate as levels in the low frequencies, participants may have been better able to hear music clearly in noisy environments at lower levels and accordingly shown lower PLLs. The current study’s overall spectrum for all participants and all musical samples differed notably from that found by Tone (2008). Tone analyzed the average frequency response curves of one musical sample for low, medium/comfortable, loud and very loud volume categories, for  57 all participants’ real-ear responses. Their results for the overall spectrum showed that dB SPL increased for all frequencies as volume increased, and the peak acoustic energy consistently fell between 1500 and 4000 Hz. These mid-frequency peaks differ from the current study’s results, for which the peak acoustic energy of the overall spectrum fell at 200 Hz. Unfortunately, Torre did not report whether or not a post hoc analysis of frequency and volume category was perforned. Hence, it is not clear in the study by Torre if dB SPL increased with volume category for some frequencies more than others as was the case for the current study. With regard to genre-specific results, the graphs of the genre-specific data given in Figures 5—7 highlight some important differences between the four genres examined. The dB (A) results specific to samples from the genres Pop, Hip-Hop/Rap, Rock and Independent Rock/Alternative in noisy environments were 68.59, 75.19, 78.32, 85.23 and dB (A) respectively. In contrast, the dB (A) results collapsed across all participants for all genres in noisy environments were 73.60 dB (A). It is possible that the small number of samples for each genre influenced the higher levels seen in 3 of the 4 genre averages, which excluded Pop. The number of samples for Pop, Hip-Hop/Rap, Rock and Independent Rock/Alternative respectively were 12, 3, 7 and 4, whereas the number of samples for the dB (A) results collapsed across all participants for all genres were 36—39. However, there are differences between the genres for both the dB (A) values and the average spectra. For instance, the individuals who listened to Independent Rock/Alternative had PLLs 12 dB higher than the average value for all song samples, which was 73.6 dB (A). Additionally, the spectra for the Independent Rock/Alternative samples were notably different from the spectra of the other genres in that there was more energy around 200,2500 and 4700 Hz. Because musical genre can influence both overall dB (A) level and frequency spectrum, it follows that realistic studies of PLD use should include musical stimuli chosen by the participants. Doing so enables researchers to account for individual differences due to each participant’s typical listening choices. The following example  58 hypothetically illustrates a potential difference in results for one participant that could occur if music samples were chosen by the researcher rather than the participant. If participant iPod 005, who chose 2 Independent Rock/Alternative and 1 Rock musical samples, were instead asked to listen to Pop music for two weeks, it is quite likely that the resulting PLLs would be much lower both because the music was not to his/her liking and because the spectra were notably different. Because the spectra for the Independent Rock/Alternative and Rock musical samples were very different from the Pop musical samples, the accurate measurement of the participant’s typical PLLs was likely facilitated by the participant-chosen stimuli included in the experimental design.  5.2  Comparison of the Current Study’s Results to Previous Studies Comparisons of the current study’s findings to previous studies were made using the  average values measured in the real-ear rather than the peak values. In the current study the mean real-ear PLLs collapsed across all participants for quiet, moderately noisy and noisy environments were 63.76, 68.50 and 73.60 dB (A), respectively. For the most part, previous studies that included real-ear or simulated real-ear measurements have found that participants’ PLLs were higher in comparison to the PLLs seen in the current study. A number of these studies had small sample sizes that were at most 3 times larger than the sample size of the current study. The sample size in the study by Serra et al. (2005) had approximately 20 participants, as 20 or fewer students participated in annual PLD output testing over a period of three years. In studies by Hodgetts et al. (2007), Torre (2008) and Abmed et al. (2007), sample sizes were 38, 32 and 24 respectively. Due to the small sample sizes of the current and previous studies, the generalizability of the results may be somewhat limited. However, at the present time these studies form an important part of the literature relating to PLD use. Previous studies that included simulated background noise reported that on average, listeners’ PLLs increased with increasing background noise, in agreement with the current  59 study’s findings (Abmed et al., 2007; Hodgetts et a!., 2007). For instance, Serra et al. (2005) demonstrated that participants’ PLLs in quiet ranged between 75—105 dB (A) Leq, when measured in artificial ears. These levels are 12—42 dB higher than those of the current study for PLLs in quiet. A potential source of the difference between these results and those of the current study may be that the age range of participants was 14—17 years old. This is a significantly younger age range than that of the current study, which was 15-44 years old with a mean of 24.77. Hodgetts et al. (2007) demonstrated that mean PLLs for earbud headphones were 77.82 in quiet, 86.66 in multi-talker babble and 88.83 dB (A) in street noise when measured in real ears. These levels are 14, 18 and 15 dB higher than the corresponding findings of the current study. A potential source of the difference between these results and those of the current study may be that Hodgetts et a!. (2007) used simulated background noise. However, Torre (2008) found comparable values to the current study for simulated real-ear measurements of 32 participants’ PLD volume levels when they were asked to adjust their PLDs to low and medium volumes. Although there was no background noise in the laboratory setting in the study by Torre, the respective values of 62.0, 71.6 dB SPL are similar to the current study’s values for PLLs in quiet and moderately noisy environments. In contrast, the mean value corresponding to a loud volume setting, 87.7 dB SPL, was 14 dB higher in the experiment by Torre than was the mean PLL value in the current study for noisy environments. A potential source of the difference between these results and those of the current study may be that participants in the study by Torre were PLD setting volume in quiet laboratory surroundings rather than background noise of any kind. Perhaps the levels corresponding to a loud subjective volume setting category in the study by Torre were higher than the mean PLLs in noisy environments in the current study because the public transit environments corresponding to participants’ noisy environments did not require loud PLD volume settings. Of the previous studies having real-ear or simulated real-ear measurements, the simulated real-ear results seen in the study by Ahmed et  60 al. bear the greatest overall resemblance to those of the current study. The mean PLLs of the 24 participants tested in simulated background noise were 62.1 dB (A) in quiet, 63.4 dB (A) in low multi-talker babble, 71.7 dB (A) in high multi-talker babble, 67.2 dB (A) in low traffic noise and 73.3 dB (A) in high traffic noise. In regards to the lack of significant differences between males and females in PLEs or volume setting in the current study, non-significant differences were also found by Hodgetts et al. (2007). However, small sample sizes were used in both the current study and the study by Hodgetts et al., namely 13 and 38, respectively. Differences in musical genre were also examined by Fligor and Cox (2004) in their study on headphone and PLD output. When played using a variety of headphones and PLDs, Rock music produced higher outputs than white noise. Additionally, Hip-Hop/Rap and Pop produced lower outputs than white noise, with Pop producing the lowest outputs. Results for differences in peak SPL between genres showed that Rock had the highest peaks (Fligor and Cox, 2004). These genre-specific output results resemble those of the current study in terms of the ranking of the genres according to overall level. However, the genre-specific data gathered by Fligor and Cox (2004) were based on only one song sample per genre. Survey results from the study by Abmed et al. (2007) also confirmed that musical genre is an important factor in participants’ choice of volume setting. The majority of survey respondents reported that they often modify their volume setting due to musical genre (Ahmed et al., 2007). With regards to objective volume settings, the results found by Ahmed et al. (2007) differ slightly from those of the current study. Ahmed et al. showed in their research that in high noise conditions, approximately 15% of participants set a test iPod at 25 to 50% of the total possible volume, and approximately 50% of participants set the iPod at 50 to 75% of the total possible volume. In contrast, the current study found that in noisy environments 31% of participants set the volume of their PLDs at 25 to 50% of the total possible volume, and 38% of participants set  61 the iPod at 50 to 75% of the total possible volume. These differences may be due to the fact that participants in the study by Abmed et al. were only using a test iPod, whereas 5 out of 13 participants in the current study were using MP3 players made by different manufacturers. As such, the average volume settings in the current study are likely different than they would have been if all participants were using iPods only. Nevertheless, as mentioned above, the real-ear results found by Ahmed et al. closely resemble those of the current study.  5.3  Limitations of the Current Study It is most likely that our study appealed to a population of listeners who were motivated  to adopt safe listening habits because the recruitment posters advertised that participants who volunteered would learn if they were potentially damaging their hearing from PLD use. A further reason may be because participants were asked to volunteer a significant amount of their time for the study. It seems unlikely that an individual would volunteer his or her time for a study about hearing if they were unconcerned with hearing protection. Indeed, results from the questionnaire indicated that all participants considered protecting their hearing to be important or very important. However, Zogby (2006) reported that 47% of teenagers and 48% of adults are not worried about acquiring hearing loss from PLD use. Further, it is possible that participants’ listening behaviours were more cautious while being monitored by an audiologist. Hodgetts et al. (2007) speculated along these lines when commenting that their participants may have selected cautious PLLs in the presence of an audiologist. Consequently, it may be reasonable to assume that the results of the current study underestimate the PLLs of typical PLD users. The impact of the high participant attrition rate noted in this study is difficult to determine. It should be noted that participants were not required to provide a reason for withdrawal from the study. Hence, any reasons discussed here are purely speculative in nature and should be interpreted with caution. It is possible that those participants who dropped out  62 were less interested than the other participants in learning whether or not their PLD listening habits were potentially damaging their hearing. If this were the case, it would nevertheless be difficult to speculate whether these participants may have had PLLs different from the means found using data from participants who finished the testing. For instance, it seems logical that an individual could have been minimally concerned about their listening habits if they always listened to their PLD at low volumes. Another possibility is that an individual might have always listened to their PLD at high volumes but knew they were unlikely to change their listening habits should testing demonstrate that their PLLs were unsafe. Regardless of the reason, it might be reasonable to assume that those participants who withdrew from the study before the second session are minimally concerned about their listening habits in comparison to those participants who completed all sessions in the study. This is because all participants were aware that they would obtain objective information as to whether or not their PLD listening habits were potentially detrimental to their hearing at the second session. However, the majority of individuals recruited (10 out of 17) were university students. Accordingly, another possibility is that exam schedules and assignment workloads may have caused time conflicts. It should be mentioned that the current study is not alone in recruiting volunteers for its participants in examining PLD use (Ahmed et al., 2007; Hodgetts et al., 2007; Torre, 2008). The results of previous research are likewise subject to the possibility that the inclusion of volunteer participants may have confounded results. Regarding subjects’ audiological results, one female participant with a unilateral absent middle-ear-muscle reflex was accepted for the study, despite the inclusion criteria given above. In the unlikely event that this influenced results, it is possible that this individual would have had lower PLLs than other participants due to limited attenuation in response to loud transient sounds on the affected side. However, the individual (iPod 002) actually had PLLs for average curves that were 8.79 dB higher in quiet, 4.05 dB higher in moderately noisy and 1.05 dB lower in noisy  63 environments. Hence, this participant’s PLLs actually increased the average values seen in this study for quiet and moderately noisy environments. Results may have been influenced by the earphones used by participants. However, significant differences in output as a function of earphone manufacturer were not found. It is possible that the variety of PLD manufacturers and earphone manufacturers of the equipment used by participants confounded results. It should also be mentioned that 2 participants’ left earphones were producing zero output, regardless of the condition of the earphones attached to the PLDs. It in not known if these anomalies impacted results. However, if there was an impact, the two participants’ PLLs would most likely have been elevated relative to their typical PLLs due to the loss of binaural loudness summation. Because all participants did not listen to identical PLDs or music selections, variability existed for factors that were not measured including maximum device output, device settings and music file sampling rate and sampling frequency. First of all, device output was not a factor of concern as only one participant out of 13 listened at maximum volume (See Table D6: iPod 004 for Moderately Noisy Environments). Second, settings on participants’ PLDs were not manipulated in this study since doing so would be contrary to our objective to gather data representative of participants’ typical listening conditions. Third, sampling rate can affect the clarity of compressed files, and may impact the user’s volume settings in that tracks compressed using lower rates may require higher settings to achieve equivalent loudness (Torre, 2008). iPods, for example, allow sampling rates of up to 320 kilobites per second (kbps). It is likely that most participants have music libraries sampled with a range of sampling rates and sampling frequencies. In this study we did not attempt to control sampling rate or sampling frequency, although we did use 3 songs as stimuli for each participant in order to average out differences among tracks in each participant’s music library.  64 The TWAN calculations were calculated using formulae designed for occupational noise, as described above. Occupational noise typically has more regular spectral and temporal characteristics than music (Hodgetts et a!., 2007). Hodgetts et al. mentioned this discrepancy as a limitation, perhaps in part because their measurements were made of overall dB (A) values and did not take into account the entire frequency spectrum. Although the use of occupational noise exposure formulae may likewise be a limiting factor in the current experiment, our design accounted for the long-term average spectrum of the music sampled in that 30 second samples were obtained for each music sample, and a frequency range of 200—8000 Hz was examined. In the current study, real ear measurements were taken for one ear only. Twelve of the thirteen participants had measurements taken from their left ear. The thirteenth participant had a significant amount of cerumen that precluded measurement in the left ear. While it is possible that this exception influenced results, it is unlikely since it affected only one set of measurements out of 13. The fact that bilateral measurements were not taken may have affected results. For example, spectral information might have been significantly different if bilateral measurements had been taken, since most music is recorded in stereo. One cannot speculate with any accuracy whether unilateral measurements underestimated or overestimated the overall levels, since recording engineers are free to mix given instruments to either the left or right channels as they see fit. Therefore, unless predictable spectral differences between left and right channels exist for unknown reasons, it is likely that any spectral differences and resulting overall level differences between channels would be due to chance alone and thus insignificant. However, it should be noted that in the current study unilateral measurements were taken in the interest of efficiency. Noise levels on public transit in Metro-Vancouver may have limited the ability to generalize the results of the current study to PLD users in other urban centres. As previously mentioned, diesel buses in Metro-Vancouver produced levels of 83 dB (A) when passing by a  65 sound level meter held at waist level at a bus stop. It is possible that diesel buses are the noisiest transit vehicles in the Metro-Vancouver transit system (City of Vancouver Bus Impact Task Force, 2000). In contrast, noise levels for subway platforms, subway car interiors, and bus stops measured in the New York City transit system reach a maximum of 106, 112 and 89 dB (A) respectively (Gershon, Neitzel, Barrera, & Akram, 2006). Hence, it is possible that participants’ PLLs in noisy (public transit) environments would have been higher had the study been carried out in an urban centre with a noisier transit system, such as New York City. Finally, the current study is limited by its small sample size. As mentioned above, it is possible that effects for gender, for example, might have been obtained with a larger sample size.  5.4  Implications of the Current Study’s Results and Directionsfor Further Research In summary, musical genre, environment and frequency weighting method have  significant effects on typical PLD users’ PLLs. These results have implications both for the public and for the scientific community. The results of the current study suggest that when assessing the TWAN dose related to an individual’s music exposure, use of the dB (A) weighting method could potentially underestimate noise exposure. This is because the music sampled in this study had peak levels in the low to mid frequencies. The dB (C) weighting or linear measurement method may be more appropriate for music, as the roll-off in the low frequencies is less marked or not touched at all by the linear measurement. In the future, noise exposure guidelines specific to music exposure should be developed. Musical genre should also be taken into account when assessing the TWAN dose related to an individual’s music exposure. Using music samples chosen by a given individual provides the most realistic picture of their corresponding noise exposure. Failing to do so can result in inaccurate conclusions regarding actual risk to hearing from PED use.  66 Although the current study reported that no participants were exceeding their daily noise dose for average curves in all environments, it is important to keep in mind that participants were volunteers who believed that hearing protection was important. Consequently, the hearing health care community should continue to educate the public about the potential risks to hearing posed by less conservative PLD use. Zogby (2006) reported that over half (58%) of teenagers would be unlikely to spend less time listening to PLDs and that 31% would be unlikely to reduce their volume settings. This apparent resistance to adopting hearing protective behaviours for PLD use is both alarming and a challenge to overcome. One approach to changing behaviours may be an expanded hearing science curriculum in elementary school that includes information and discussion about safe PLD use. Another approach might be provision of relevant information online on sites where PLD users often download music. Finally, Zogby (2006) reported that both adults and teenagers believed the Internet would be an effective means by which to educate the public about safe listening habits. PLD manufacturer initiatives to promote safe listening habits may be an important aid to behaviour modification, and their development should be encouraged. One example is the iPod’s optional volume limiting option. Apple provides this option in order to encourage iPod users to practice safer listening habits and to refrain from listening at full volume. However, in the current study we found that no participants with iPods reported use of the volume limiting option. Although the current study has a small sample size, these reports suggest that an optional volume limiting feature is not often employed by listeners. Instead of an optional feature, it may be more effective for PLD manufacturers to limit the actual output that can be generated by PLDs in order to limit excessively loud music listening among PLD users. Given that environment significantly impacted participants’ PLLs and that frequency spectrum significantly interacted with environment such that low frequencies increased more than high frequencies with increased volume settings, manufacturers could develop headphones  67 that produce linear changes in frequency response with increased volume settings. Perhaps listeners would not feel the need to increase their volume settings in increasingly noisier environments with such headphones if the sound quality and frequency response was good for all volume settings, in comparison to earbuds. One possibility that may not be feasible at the current time would be to develop a PLD noise dose log function in the PLD software. Such a function could keep track of both listening duration and overall output for an average ear canal at the selected volume setting per day. Future studies on the topic of PLD use should apply realistic experimental designs similar to that of the current study and employ random sampling of participants. Should high schools and high school students be interested in taking part in such future studies, the use of random sampling from this population would be convenient and increase the likelihood that a more representative picture of the PLD listening habits could be obtained. Additionally, the impact of binaural measurements and controls for sampling rate and sampling frequency should be investigated. Finally, methods of frequency weighting appropriate to music should be further investigated in the aim of developing a noise exposure guideline specific to music exposure. In conclusion, this investigation of PLD use has produced results in support of the argument that assessment of an individual’s risk to hearing from PLDs should take moderating variables into account. Specifically, the frequency weighting method and PLD users’ typical listening environments and musical choices are significant factors in the risk posed by actual PLD listening habits that are not often measured via controlled laboratory studies alone.  68 References Aarts, R. M. (1992). A comparison of some loudness measures for loudspeaker listening tests. Journal ofAudio Engineering Society, 40(3), 142—146. Act Respecting Occupational Health and Safety [R.S.Q., c.2.1]. Regulation respecting Occupational Health and Safety (O.C.885-2001). Division XV, Sections 130—140. Abmed, S., Fallah, S., Garrido, B. Gross, A., King, M., Morrish, T. et al., (2007). Use of portable audio devices by university students. Canadian Acoustics, 35(1), 1—18. American Academy of Audiology. 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Criteria for a Recommended Standard: Occupational Noise Exposure. Revised Criteria. http://www.cdc.gov/98- 1 26.html  72 Obeling, L. & Poulsen, T. (1999). Hearing ability in Danish Symphony Orchestra musicians. Noise Health, 1(2), 10—27. Occupational Safety and Health Administration. (1981). Occupational noise exposure: Hearing conservation amendment. Federal Register, 46, 4078—4179. Occupational Safety and Health Administration. (1983). Occupational noise exposure: Hearing conservation amendment; Final rule. Federal Register, 48, 973 8—9785. Peng, J.-H., Tao, Z.-Z., & Huan, Z.-W. (2007). Risk of damage to hearing from personal listening devices in young adults. The Journal of Otolaiyngology, 36, 181—185. Royster, J. D., Royster, L. H. & Killion, M. C. (1991). Sound exposures and hearing thresholds of symphony orchestra musicians. Journal ofthe Acoustical Society ofAmerica, 89(6), 2793—2803. Saunders, G. H., Morgan, D. E. (2003). Impact on hearing aid targets of measuring thresholds in dB HE versus dB SPE. International Journal ofAudiology, 42, 319—326. SCENIHR (Scientific Committee on Emerging and Newly-Identified Health Risks). (2008). Scientific opinion on the potential health risks of exposure to noise from personal music players and mobile phones including a music playing function, 23 September 2008. Serra, M. R., Biassoni, E. C., Richter, U., Minoldo, G., Franco, G., Abraham S. et a!. (2005). Recreational noise exposure and its effects on the hearing of adolescents. Part I: An interdisciplinary long-term study. International Journal ofAudiology, 44, 65—73. Tan, T. C., Tsang, H. C. & Wang, T. L. (1990). Noise surveys in discotheques in Hong Kong. Industrial Health, 28, 37—40. Thiery, L., & Meyer-Bisch, C. (1987). Hearing loss due to partly impulsive industrial noise exposure at levels between 87 and 90 dB(A). Journal ofthe Acoustical Society of America, 84, 65 1—659.  73 Torre, P. III. (2008). Young adults’ use and output level settings of personal music systems. Ear & Hearing, 29(5), 1—9. Vogel, I., Brug, J., Hosli, E. J., van der Ploeg, C. P. B., Raat, H. (2007). Young people’s exposure to loud Music: A summary of the literature. American Journal ofPreventive Medicine, 33(2), 124—133. Vogel, I., Brug, J., Hosli, E., van der Ploeg, C. P. B. & Rant, H. (2008). MP3 players and hearing loss: Adolescents’ perceptions of loud music and hearing conservation. The Journal of Pediatrics, 152, 400—404. Williams, W. (1995). Noise exposure of orchestra members. Chatswood, Australia, National Acoustic Laboratories. (Report no. 109). Worksafe BC. Basic noise calculations. April, 2007. Available at: http://www.worksafebc.com! publicationsea1thandsafety/by_topic/assets/pdf/basic_noise_ca1cu1ations.pdf. Accessed Nov. 14, 2008. Worksafe BC. How loud is it? General industry. Available at: http://www2.worksafebc.com! Topics/HearingLossPreventionlResources.asp. Accessed Dec. 10, 2008. Zogby International. Survey of teens and adults about the use of personal electronic devices and head phones. March 14, 2006. Available at: http://www.asha.org/NRJ rdonlyres/1 OB67FA1 -002C-4C7B-BAOB- 1 C0A3AF98A63/0/zogbysurvey2006.pdf. Accessed Nov. 10, 2007.  74 Appendix A  The University of British Columbia Consent Form Project Title: Determining Preferred Listening Levels of a Personal Listening Device in Teenagers and Adults in Real life Environments Using Real Ear Measures. Principal Investigator:  Co-investigators:  Dr. Navid Shabnaz Assistant Professor, School of Audiology & Speech Sciences University of British Columbia  Dr. Lorierme M. Jenstad Assistant Professor, School of Audiology and Speech Sciences University of British Columbia  Cheryl Lane M.Sc. Candidate School of Audiology and Speech Sciences University of British Columbia  Introduction: You are being invited to take part in this study because you frequently use an Apple iPod or MP3 player, and commute to your school or work using public transit.  Purpose: The aim of this study is to determine whether the average volume settings for iPods and MP3 players, as set by typical users in their every day listening environments, are sufficiently high to damage hearing, when measured in the ear using music chosen by the subject. Using information from a listening log and using music chosen by the subject will mean that the results obtained are more representative of what happens in the real world. These results could be used to increase public awareness of the real-world potential for hearing loss resulting from the use of iPods and MP3 players, and to promote the adoption of guidelines to ensure a safe listening volume for consumers of recreational music.  75  Procedure: If you agree to participate in this project, all testing will be done by a master’s student under supervision of a certified audiologist. The testing uses safe and routine procedures to assess hearing, health of the auditory system, and the level of sound in the ear canal. Two testing sessions will be necessary, including today. You will be asked to keep a log of your average listening volumes for two weeks while using your iPod or MP3 player, including listening durations at these volumes, in three common listening environments (quiet, cafeteria/coffee shop, and public transit). You will also be asked to complete a questionnaire about hearing, hearing protection, exposure to loud noises, etc. The first session will involve the hearing test. The audiology student will look in your ears to make sure that they are clear, and then place small foam earphones in your ears. You will be asked to listen for quiet tones and press a button whenever you hear them. Then, you will be asked to do the same thing while wearing a snugly fitting headband which tests how well you hear when sound travels through bone. Next, a snugly fitting rubber plug will be placed in your ear, and you will hear some tones and feel some pressure changes similar to those you feel on an airplane. The testing for session 1 will take up to 45-50 minutes and the results will be given to you immediately afterward. If the results show that your hearing is normal, you will be able to continue in the study.  Prior to the second session, you will be asked to email your completed listening log and questionnaire to the audiology student if possible. Session 2 will take approximately 40 minutes. During the second session, measurements will be made inside your ear using three songs you have chosen that represent three different genres that you listen to most, and using information from your listening log. A small tube, which is attached to a microphone, will be put inside your ear canal, close to but not touching your eardrum. Insertion of this tube causes at most a risk of discomfort and minor irritation, as the skin inside the ear can be sensitive. The audiology student  76 will take a look inside your ear to make sure the tube is in the proper place, and use a small piece of tape outside your ear to secure the other end. You will listen to portions of the three songs in both ears, while the machine connected to the microphone analyzes the sound inside your ear. Afterwards, you will learn whether or not the levels you been listening to your iPod or MP3 player may have been damaging your ear for the length of time you had been listening to them.  Your participation in these tests is entirely voluntary. You may withdraw from this study at any time and without providing any reasons for your decision. Should you decide to withdraw from this study all the data collected before your withdrawal will be discarded permanently from our database. Withdrawal will in no way jeopardize your present or future university associations or coursework.  Inclusion and Exclusion Criteria: You are eligible to participate in this study if you have normal hearing, use your iPod or MP3 player 1 hour or more per day, and are an adult or high school student who commutes to school or work on public transit.  Benefits: There are no direct benefits to subjects for participating in this study. All participants will receive a free hearing test. Participants will also learn whether the levels at which they listen to their iPod or MP3 players in different environments and for different lengths of time are capable of damaging their hearing.  Risks: All procedures in our testing sessions are well established clinical practices, which pose no risk to your health. Apart from the time required to perform the tests and complete the forms, there are no foreseeable disadvantages. There is a potential for loss of confidentiality.  __________________________,  77 Payment: In addition, participants will be reimbursed a total of $10 for their time.  Testing Venue: The testing will take place at the UBC School of Audiology and Speech Sciences.  Confidentiality: Your identity will be coded using a code known only to the researchers, and all information that is collected from you will remain confidential. Only group results or coded individual results will be given in any reports about the study. Coded results only (no personal information) will be kept in computer files on a password protected hard drive. Your confidentiality will be respected. No information that discloses your identity will be released or published without your specific consent to the disclosure. However, research records and medical records identifying you may be inspected in the presence of the Investigator or his designate by representatives of Health Canada, and the UBC Research Ethics Board for the purpose of monitoring the research. However, no records which identify you by name or initials will be allowed to leave the Investigators’ offices. Compensation for Injury: Signing this consent form in no way limits your legal rights against the sponsor, investigators, or anyone else.  Consent: I,  have read the above test protocol and I consent to  participate in this study undertaken by Drs. Navid Shahnaz and Lorieime M. Jenstad, and Cheryl Lane at the School of Audiology & Speech Sciences. The researchers assure me that my  78 participation in this experiment is completely voluntary and that I may withdraw from this research at any time without consequences.  If I have any question or desire further information with respect to this study, I may contact Dr. Navid Shahnaz. If I have any concerns about my treatment or rights as a research subject, I may contact the Research Subiect Information Line at the University of British Columbia, at 604-8228598.  I have received a signed and dated copy of this consent form for my records.  Subject name (please print)  Subject signature  Date  Witness name (please print)  Witness signature  Date  Name of principal/co-investigator  Signature of principal/  Date  lease print)  co- investigator  79 Appendix B  Listening Log Subject Code:_____________________ Questions? Please email the researcher. Please list the Genre, Title, Performer(s) and Composer (if known) of 3 Songs/Pieces of your choice to be used for Lab Measurements: 1) 2) 3)  Please list your most common Listening Environments: 1) Quiet (e.g. at home, in the library):________________ 2) Moderately noisy (e.g. cafeteria, coffee shop):___________________ 3) Noisy (e.g. public transit):____________________________  For the next 14 days, please record the volume setting at which you listen to your MP3 player in the above 3 environments. If your MP3 player displays volume bars when you adjust the volume, record the number of the volume bar at which you set it out of the total number of volume bars (e.g., 7/10 volume bars on public transit on day 12). If your MP3 player displays numerals when you adjust the volume, record the ratio of the numeral corresponding to the volume you set it out of the highest numeral possible (e.g. 15/20 in quiet on day 3). If your MP3 player has neither volume bars nor numerals, please use the ruler sleeve provided, labeled with numbers 1-10. To determine the numerical value, adjust the volume to your chosen level, and choose the number (e.g. 3) or the midpoint between two numbers (e.g. 3.5) that best lines up with the location of the volume indicator on the MP3 player.  80 If you find that you must adjust the volume numerous times in a given environment, record the average volume at which you set the device. If you find yourself listening to the device in a given environment more than once per day, please record the volume setting for the additional incident(s) if you are listening to music in that environment for 15 minutes or more. Space is provided in the tables for you to record volume settings for up to 5 incidents in each environment, if needed. Please also record the duration of time you spend in each environment every time you record a volume setting. Please indicate if you are recording minutes or hours in the tables:_____________________ Please indicate which volume measurement system applies to your MP3 player/iPod: U Automatic numerical volume indicators U Volume bars (Total number of bars:_____________ U Ruler sleeve provided (numbered 1-10)  DAY1  1  Volume_Seffin.& Incident # 2 4 3  5  1  Duration in Environment Incident # 2 4 3 5  1  Duration in Environment Incident # 2 3 4 5  Quiet Moderately Noisy Noisy DAY2  1 Quiet Moderately Noisy Noisy  Volume Setting Incident # 2 4 3  5  Tj  Cl)  Cl)  0  o  o  L’J  o  o  cM  0  Cl)  0  0  -  cM  0  Cd)  0  0  -  rn  I  r 0  Cl)  0  0  cM  t’J 0  00  C  fi.  tJ’  C)  F.  1: CD  C)  31:  k)  I  I.  I  C’)  C  0  CD  C’)  0  0  CD  CD  CD  C  C  C  C  C  41:  CD  C)  I  I.  Cl)  0  I. E. CD  (.J  -  CD  C)  31:  C)  I I  83 DAY 13  1  Volume Setting Incident # 2 4 3  5  1  Duration in Environment Incident # 2 3 4 5  1  Duration in Environment Incident # 2 3 4 5  Quiet Moderately Noisy Noisy DAY 14  1  Volume Setting Incident # 2 3 4  5  Quiet Moderately Noisy Noisy AVERAGES Please email this form to the researcher, or fax it to the School of Audiology identified only by your subject code and “Attention Cheryl Lane Re: iPod Study” before session 2 so the averages can be calculated by the researcher ahead of time, or bring it to the session and allow an extra 10 minutes for session 2.  84 Appendix C Questionnaire Subject Code:___________  1. Have you read, seen, or heard any information regarding hearing loss, recently or otherwise? (If no, go to question 4) DYes DNo 2. What information have you learned about hearing loss?  3. Where did you learn this information?  4. Do you think that use of a personal music player can damage your hearing? (If no, go to question 6) DYes DNo 5. What factors do you think can determine the likelihood of hearing damage when using a personal music player?  85 6. How likely would you be to use each of these strategies to reduce hearing damage at a concert/club etc.? Please check the boxes that apply.  Very Likely  Likeliness to Use Strategy Likely Somewhat Likely  Not Likely  Wear brightly coloured foam earplugs Wear clear/fleshcoloured earplugs Situate yourself away from speakers Stay for a limited amount of time  7. Have you ever worn earplugs at a concert, etc? DYes DNo 8. Have you ever experienced ringing in your ears after attending a noisy event? DYes DNo 9. How often do you attend concerts? O  0 0 0 0  More than once a week Between once a week and once a month Once every couple of months Once or twice a year Never  10. Have you ever had any problems related to hearing, such as ear pain, ringing in your ears or difficulty hearing? (If no, go to question 12) DYes ONo  86 11. Specifically what kind of hearing or ear related problem have you experienced? (Please check all that apply) El ear disease El trouble hearing El ringing in your ears El ear infection El ear-related dizziness or spinning sensation El other (please specify:______________________________________________ 12. Do you feel that you must turn the television or radio to a higher volume than most of your peers? El Yes ElNo 13. Do you think that you listen to television or radio at very soft, soft, moderate, loud or very loud volumes?  14. Do you listen to music while working on the computer? (If no, go to Question 16) El Yes ElNo 15. Do you use headphones while listening to music on the computer? El Yes ElNo 16. How long have you been using an MP3 player?  17. What brand of MP3 player do you use? 18. How often have you used a personal listening device such as a walkman, CD player with headphones other than an MP3 player? El Very often El Often El Somewhat often El Not often El Never 19. How often do you listen to music in a car (without headphones)? El More than 3 hours a day El 1-2hoursaday El Less than 1 hour a day El Never  ________# ________# ________#  ________________________ _______#  87 20. Have you spent a lot of time in a noisy environment where the noise was not music (e.g. construction noise, factory noise, etc.)? U Yes —If yes, please list environment U No—If no, please go to Question 22 21. About how much time did you spend in this environment? of months U Every day for of years U Every day for of hours for U Every week for of hours for O Every week for U Other  of months of years  22. How important do you feel it is to protect your hearing? U Very Important U Important U Somewhat Important U Not Important  Questions adapted from Zogby (2006) and Chung, Des Roches, Meunier & Eavey, (2005).  .  a v -3 C 0 0  -  )  4 .i a 0 0 Vi  t’3  0  .  -  C Vi V V Vi O Vi t 00 0 0 — Vi ‘.0 00 —a .  -‘  4 0 00  oo  W  .  -  .  Vi —i  0’.0  —  .  —  -  .  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O, Q \C VI 0— VI  C .  .  . .  .  0% 0 -  —  -  —  —  —  0% 0 . k)  —  —  —  —  VI VI VI VI VI 0 0 0% 0% 0% Q 0% 00 50 0% .1 SO — 00 00 50 . VI VI 0’ 00 VI 00 . ‘ — SO VI U) VI 0 0 — — 50 —  C  0 . 0%C  t’J 0 —. t) . 0 —] 0 50 50 -1 00  CSO  VIVI-  -.  ..  C Q 0’, 0’, C’ L) k) l) W . . 0% VI 00 —  VI Vi VI . . 4 4 VI VI VI VI VI VI VI 0 0 0 —a 00 00 0 4 C C \ \ t’) VI .) 0 -. . — VI 00 — — VI C 4 c W 00  C O O Q SO VI W  .  -  .  VI VI VI VI VI VI VI VI VI VI VI VI VI Q% 0% VI C’, 0% - 0 0 - 0% VI VI VI U) VI 0 50 0 0 0% VI 0 SO 4 00 . —LI 50 0 .) eQ . - VI 50 50 00 0’, 50 C VI00 t3 — 00 — 0 0 U) .l -) . . VI . U) 50 .1 0 50 t’J — —‘ 00  U) U) U) U) . . 4  —  00%SOVI VI  O C C, 0% 0%  4 4 4 4 4 4 4 . 4 . 00 O 0 VI 00 O - 0— 00 4 .  00 ‘J SO 0% VI 0% 0 t’3 — 00 0 0 4 — 00 50 0’, W 50 0’, VI ‘J 0 W 0 — ‘) I’3 0’ % 0% ‘ 0 G’  4 VIO t’)CVI  0 O O 0’, 0’, 0% VI —J 0 )  -  4  ocooc  ‘J t’-) k) -‘ — -. — -‘ -‘ oc00c  0000000 00000000000000000000  k) ‘J  4 . 4 VI C’, 0 —a —a -  VI 50 0 U) . U) 50 U) VI VI VI k) U) 00 —a o k) . 0 0 VI  - VI -‘  —  -i - —a - - —a —a 0% 0’ J0:-a U) 0% . 1500 0% VI 00 U) VI 0’, J VI VI . i—’ VI 00  VI 0  U) 00  0’, 0’, o’,  00  —  0% 50  U) 00  -  —  0  —  0 4  —  -.  —  —a  J  -  U) 00 VI . I— 0’, 00 I’) U) 0000 VI 00 —a SC) SO  0% 0% 0 0-, o 0-, 0% 0% 0’, —a  0%-0%0%W00VI0000%00%500000%0%U)000’k)k)U)  VI00500050O0Q)O  U) 50 0 50 00 00 0% U) J -‘ -.J VI 00 %J 0% U) 00  ‘-  .  00 0 VI 0 00 VI 0 -I  0 ) VI c — 0 00 — 0 0 0 VI 00 VI 00 VI -3 W 00 50 0000 0  0%.VI  o o  .  -  Q \D 0 L’J 4  —1  o0oooooooooo00  00  0  0  CiD  ‘.4  —.  C  C  —  -  —  C  ___________  _____  _____  124 Appendix E  The University of &,i& CoAunbie Offke of Research Seri4tee CTh.icaI Researth Ethics Board- Pcx,m 210, 228 Weut 10th Avenue, Vancouver, BC VZ ILS  ETHICS CERTIFICATE OF EXPEDITED APPROVAL N$TJTUTON / DEPARTMENT: — JBC CREEl NUMBER: JBC/Medicine, Facufty of/Audiology & Yin Shahnaz speech Scnces TnTHEi&RcH vAii E CAArnED OUT: PRSICFAL INVESTIGATOR  *________  [  site 1 Vancotwer (excludes LC Hospital)  jLC  IoIons vwe the r.w,d, ‘4 beon&ded: 1th.r A  COINVESTJGATOR(S: cberyl Mcole Lane ..otienna Jenstad  frA POJECT TWLEz jinfluences of Liste ring Log Data and Subject-Chosen Stmuh on Preferred Listening Leve of Normal Hearg Adultswho requently Use a Personal Listening Device. THE CuRRENT UBC CREEl APPROVAL FOR THIS STUDY EXPIRES Februaiy 12 2009 the LC CUncal Research Etlcs Board Chak or Assocle Chak has revlowedtheeboveescnbedresearchect,inckn associsted docunentation nsted below, and finds the research prcect acceptab on tcal groi.iids tr research invoWing hunoi stjects and hereby grards approv.  DOcUMENTS I1LUDED I4TIHSAPPROVAL  R0 DATE:  _LcJ rrOtoCOk  o.  Revised Protocol C0t Fornis:  1  December 4, 2007  evised Consert  1  December 4, 2007  LMvertements: December  IPOD Ret uitmer Poster Questlonnaire Quastionnake Cover  0 uesiionnare  Februaty IZ 2008  4  2007  Letter, Tests: December 4,  2007  1CERTIFlCATIO in respect of dllnkal tris: I. The merntership of this Research Ethics Board oon?phes with the rnemberthp requIrements for Research Ethics Boards delined rn D?.iision 5 of the Food end Drug Regulations. 2. The Research Eth/cs Board carries out its functions in a manner consient with Good Clinical Practices  125  Ia  This Research Ethics Eoard has reviewed and approved the clinical trial protocol and informed consent form for the trial which is to be conducted Eq the qualified investigator named above at the oecified clinical trial site. This approval pnd the views of this Rearch Ethics Ecard have teen documented in writing.  The documentation included for the above-named project has been reviewed by the UBC CREB, and the research study, es presented in the documentation, was found to be acceptable on ethical grounds for research involving human subjects and was approved by the UBC CREB. Approval of the Clinical Research Ethics Board ty:  Dr. Caron Strahiendorl, Associate Chair  

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