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Perception of the missing fundamental in patients with low frequency hearing loss Horvath, Gary Paul 1988

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PERCEPTION OF THE MISSING FUNDAMENTAL IN PATIENTS WITH LOW FREQUENCY HEARING LOSS By GARY PAUL HORVATH B.Sc. (Hons.), The University of B r i t i s h Columbia, 1984 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES (Department of Physiology) We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA October 1988 (c)Gary Paul Horvath, 1988 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of Physiology The University of British Columbia 1956 Main Mal l Vancouver, Canada V6T 1Y3 Date October 17, 1988  DE-6G/81) ABSTRACT The p e r c e p t i o n of the p i t c h of a harmonic complex tone missing i t s fundamental frequency was i n v e s t i g a t e d i n p a t i e n t s with u n i l a t e r a l s e n s o r i n e u r a l low-frequency hearing l o s s . Using a t w o - a l t e r n a t i v e f o r c e d choice adaptive method and an adjustment technique, p a t i e n t s matched the p i t c h of a complex tone c o n s i s t i n g of the 3rd-7th or 3rd-10th harmonics, with a pure tone. Component f r e q u e n c i e s were chosen such that they would f a l l w i t h i n the i n t a c t p o r t i o n of the p a t i e n t ' s damaged ear, but whose fundamental frequency would f a l l w i t h i n the damaged frequency area. P i t c h matches were made monaurally and b i n a u r a l l y , with and without low-pass f i l t e r e d n o i s e . R e s u l t s i n d i c a t e d that the p a t i e n t s tended to match the p i t c h of the l a c k i n g fundamentals to the complexes even though the frequency of the r e s i d u e p i t c h f e l l w i t h i n the range of e l e v a t e d pure tone t h r e s h o l d s . I t i s concluded that i n f o r m a t i o n r e g a r d i n g the r e s i d u e p i t c h i s not mediated by c o c h l e a r nerve f i b e r s with c h a r a c t e r i s t i c f r e q u e n c i e s corresponding to the fundamental. Temporal cues c a r r i e d by f i b e r s with c h a r a c t e r i s t i c f r e q u e n c i e s corresponding to the p a r t i a l s w i t h i n the complex stimulus are most l i k e l y i n v o l v e d i n p i t c h p e r c e p t i o n . I i TARLE OF CONTENTS Abstract i i L i s t of Abbreviations v L i s t of Tables v i L i s t of Figures v i i i Acknowledgements xi Introduction 1 Methods : 17 A. Subjects 17 B. Stimuli 18 C. Procedure 19 Pure Tone Audiogram 19 Pitch Training 20 Pitch Matching of Complex Tones Using a Two-Alternative Forced Choice Adaptive Method 21 Pitch Matching of Complex Tones Using an Up-Down Adjustment Technique 28 D. S t a t i s t i c a l Analysis 30 Results 31 Pure Tone Audiograms 31 Pitch Matching of Complex Tones Using a Two-Alternative Forced Choice Adaptive Method....38 i i i TABLE OF CONTENTS (CONT.1 i ) P i t c h Matching C o n t r o l 99 i i ) P i t c h Matching C o n t r o l with Noise 99 i i i ) P i t c h Matching Between Ears 100 iv) P i t c h Matching Between Ears with Noise 101 P i t c h Matching of Complex Tones Using an Up-Down Adjustment Technique 102 i ) P i t c h Matching C o n t r o l 102 i i ) P i t c h Matching C o n t r o l with Noise 113 i i i ) P i t c h Matching Between Ears 113 iv ) P i t c h Matching Between Ears with No i s e 114 Discuss ion 123 B i b l i o g r a p h y 140 i v L I S T OF A B B R E V I A T I O N S approx. approximation bel. below betw. between dB decibel, freq. frequency fund. fundamental har. harmonic HL hearing l e v e l Hz hertz kHz kilohertz mm millimeter msec millisecond MHz megahertz oct. octave P.M. pitch matching sec sec SEM standard error of the mean seq. sequence SL sensation l e v e l SPL sound pressure l e v e l s t a r t . s t a r t i n g w. with v T.TST DF' T A B L E S Table 1: Stepsizes of the Comparison Pure Tone (£2) 26 Table 2: Decrease in Threshold with Increasing Frequency for Each Patient... 36 Table 3: Selection of Components for the Complex Test Sound Used in the Pitch Matching Experiments 37 Table 4: Pitch Values Assigned to the Pitch of the Complex Test Sound by Patient A.D. Using the Two-Alternative Forced Choice Adaptive Routine 87 Table 5: Pitch Values Assigned to the Pitch of the Complex Test Sound by Patient A.F. Using the Two-Alternative Forced Choice Adaptive Routine 89 Table 6: Pitch Values Assigned to the Pitch of the Complex Test Sound by Patient G.F. Using the Two-Alternative Forced Choice Adaptive Routine 91 Table 7: Pitch Values Assigned to the Pitch of the Complex Test Sound by Patient L.F. Using the Two-Alternative Forced Choice Adaptive Routine 93 Table 8: Pitch Values Assigned to the Pitch of the Complex Test Sound by Patient R.L. Using the Two-Alternative Forced Choice Adaptive Routine 95 Table 9: Pitch Values Assigned to the Pitch of the Complex Test Sound by Patient J.W. Using the Two-Alternative Forced Choice Adaptive Routine 97 vi LIST OF TABLES (CONT.) Table 10: Pitch Values Assigned to the Pitch of the Complex Test Sound by Patient A.D. Using the Up-Down Adjustment Technique 103 Table 11: Pitch Values Assigned to the Pitch of the Complex Test Sound by Patient A.F. Using the Up-Down Adjustment Technique 105 Table 12: Pitch Values Assigned to the Pitch of the Complex Test Sound by Patient G.F. Using the Up-Down Adjustment Technique 107 Table 13: Pitch Values Assigned to the Pitch of the Complex Test Sound by Patient L.F. Using the Up-Down Adjustment Technique 109 Table 14: Pitch Values Assigned to the Pitch of the Complex Test Sound by Patient R.L. Using the Up-Down Adjustment Technique I l l Table 15: Summary of the Number of Matches to either the Fundamental and i t s Octaves, or to the Odd Harmonics and the Octaves below these P a r t i a l s 116 Table 16: Summary of the Number o£ Matches to either the Missing Fundamental, or to the Presented P a r t i a l s 120 v i i T . T B T O F F I G U R E S Figure 1: Damaged and Intact Ear Audiograms of Patients A.D., A.F., and G.F 32 Figure 2: Damaged and Intact Ear Audiograms of Patients L.F., R.L., and J.W 34 Figure 3: Data from the Pitch Matching Control Procedure for Patient A.D. Using the Two-Alternative Forced Choice Adaptive Method 39 Figure 4: Data from the Pitch Matching Control with Noise Procedure for Patient A.D. Using the Two-Alternative Forced Choice Adaptive Method 41 Figure 5: Data from the Pitch Matching Between Ears Procedure for Patient A.D. Using the Two-Alternative Forced Choice Adaptive Method 43 Figure 6: Data from the Pitch Matching Between Ears with Noise Procedure for Patient A.D. Using the Two-Alternative Forced Choice Adaptive Method 45 Figure 7: Data from the Pitch Matching Control Procedure for Patient A.F. Using the Two-Alternative Forced Choice Adaptive Method 47 Figure 8: Data from the Pitch Matching Control with Noise Procedure for Patient A.F. Using the Two-Alternative Forced Choice Adaptive Method 49 Figure 9: Data from the Pitch Matching Between Ears Procedure for Patient A.F. Using the Two-Alternative Forced Choice Adaptive Method 51 Figure 10: Data from the Pitch Matching Between Ears with Noise Procedure for Patient A.F. Using the Two-Alternative Forced Choice Adaptive Method 53 v i i i LIST OF FIGURES (CONT.) Figure 11: Data from the Pitch Matching Control Procedure for Patient G.F. Using the Two-Alternative Forced Choice Adaptive Method 55 Figure 12: Data from the Pitch Matching Control with Noise Procedure for Patient G.F. Using the Two-Alternative Forced Choice Adaptive Method 57 Figure 13: Data from the Pitch Matching Between Ears Procedure for Patient G.F. Using the Two-Alternative Forced Choice Adaptive Method 59 Figure 14: Data from the Pitch Matching Between Ears with Noise Procedure for Patient G.F. Using the Two-Alternative Forced Choice Adaptive Method 61 Figure 15: Data from the Pitch Matching Control Procedure for Patient L.F. Using the Two-Alternative Forced Choice Adaptive Method 63 Figure 16: Data from the Pitch Matching Control with Noise Procedure for Patient L.F. Using the Two-Alternative Forced Choice Adaptive Method 65 Figure 17: Data from the Pitch Matching Between Ears Procedure for Patient L.F. Using the Two-Alternative Forced Choice Adaptive Method 67 Figure 18: Data from the Pitch Matching Between Ears with Noise Procedure for Patient L.F. Using the Two-Alternative Forced Choice Adaptive Method 69 Figure 19: Data from the Pitch Matching Control Procedure for Patient R.L. Using the Two-Alternative Forced Choice Adaptive Method 71 lx L I S T OF F I G U R E S ( C O N T . ) Figure 20: Data from the Pitch Matching Control with Noise Procedure for Patient R.L. Using the Two-Alternative Forced Choice Adaptive Method 73 Figure 21: Data from the Pitch Matching Between Ears Procedure for Patient R.L. Using the Two-Alternative Forced Choice Adaptive Method 75 Figure 22: Data from the Pitch Matching Between Ears with Noise Procedure for Patient R.L. Using the Two-Alternative Forced Choice Adaptive Method 77 Figure 23: Data from the Pitch Matching Control Procedure for Patient J.W. Using the Two-Alternative Forced Choice Adaptive Method ...79 Figure 24: Data from the Pitch Matching Control with Noise Procedure for Patient J.W. Using the Two-Alternative Forced Choice Adaptive Method 81 Figure 25: Data from the Pitch Matching Between Ears Procedure for Patient J.W. Using the Two-Alternative Forced Choice Adaptive Method 83 Figure 26: Data from the Pitch Matching Between Ears with Noise Procedure for Patient J.W. Using the Two-Alternative Forced Choice Adaptive Method 85 x ACKNOWLEDGEMENTS I would l i k e to express my sincere gratitude to my supervisor, Dr. Di e t r i c h Schwarz, for his encouragement and guidance throughout the duration of t h i s project. I would also l i k e to thank Ward Tomlinson and Joseph L i for their expert advice and help with instrumentation and computation. xi INTRODUCTION H i s t o r i c a l Review The pitch of complex sounds has long been a controversial subject. In 1843, G.S. Ohm formulated a rule by which the ear analyses complex musical tones, and thi s was later known as "Ohm's acoustical law". According to Ohm, a complex of musical tones is being analysed as a sum of sinusoidal o s c i l l a t i o n s . The ear senses these simple tones, each of which corresponds to one simple sinusoid, whose pitch is determined by the corresponding period. The sensation of a musical tone is therefore compounded out of the sensations of several simple tones. The prime tone being generally louder than any of the upper p a r t i a l tones, would alone determine the pitch of the complex (Helmholtz,1954). Ohm's law contradicted the hypothesis put forward by Seebeck in 1841. Using an acoustic siren as a sound generator, Seebeck found that although the part-tone at the fundamental frequency corresponding to the pitch of a musical sound was subjectively strongest, the objective strength of that p a r t i a l could be rather weak or absent. He concluded that the pitch of the musical sound is determined by the period of the signal's waveform and not by the 1 frequency of the lowest component (Seebeck,1841; de Boer,1976) . Ohm demonstrated mathematically that the musical sounds generated by Seebeck must have contained fundamental components of greater strength than reported by him (Ohm, 1843 ). Showing once more that the objective strength of the fundamental could not correlate with the subjective strength, Seebeck (1843) counterargued that in a musical tone containing several simple tones, a portion of the int e n s i t y of the higher harmonics serve to strengthen the percept of the fundamental. Ohm (1844) f i n a l l y conceded that i t was an " i l l u s i o n of the ear" to apprehend the higher harmonics e n t i r e l y or p a r t l y as a reinforcement for the complex tone whose pitch is determined by the fundamental. The notable German s c i e n t i s t Helmholtz (1954) supported Ohm and provided a physiological account for auditory analysis. He proposed that d i f f e r e n t frequencies w i l l excite d i s t i n c t resonating areas along the basi l a r membrane, and that information about an individual p a r t i a l w i l l be carried only by the nerve fibers innervating the corresponding area along the membrane. Thus pitch and other q u a l i t i e s of tones would be explained by the location of excited nerve f i b e r s . Later studies by von Bekesy (1960) on the s p a t i a l frequency analysis of sound in the cochlea, together with 2 the work of Helmholtz, led to the formulation of the "place theory" of hearing. This theory postulates that the frequency components of a complex sound are represented at certain places in the cochlea where they e l i c i t maximal displacement of the basi l a r membrane. High frequency stimuli maximally displace the basal portion of the membrane, and low frequency stimuli the apical part. This displacement causes a chain of events leading to the stimulation of nerve fibers at a particular location. The tone sensation a r i s i n g from this stimulation w i l l have a pitch corresponding to the c h a r a c t e r i s t i c frequency for that locat ion. The place theory can thus be thought of as consisting of two mechanisms. The analysing mechanism s p a t i a l l y analyses a complex sound into i t s sinusoidal components on the b a s i l a r membrane, whereas the transmitting mechanism w i l l transmit information regarding the pitch of the complex along those neural fibers innervating the points of ~ maximal displacement of the membrane. Seebeck's work had been largely forgotten u n t i l a major set-back for the "place" model arose from the work of Schouten in the 1940's (Schouten,1940a,b,c). Using an optic siren to produce periodic signals of any desired waveform, Schouten (1940c) cancelled the fundamental tone of a complex stimulus whose fundamental frequency and pitch 3 corresponded to 200 Hs. He found t h a t the sharp note o£ 200 Hz remained unchanged, s t i l l p r e s e n t i n the p e r c e i v e d sound. Moreover , a f t e r r e i n t r o d u c i n g the fundamental tone to the sound, i t was heard s e p a r a t e l y as a pure tone h a v i n g a p i t c h of 200 Hz but whose loudness was low compared to t h a t of the second and t h i r d harmonic . The sound a c c o r d i n g l y c o n t a i n e d two components whose p i t c h was tha t of 200 Hz. One component h a v i n g a pure tone q u a l i t y was i d e n t i c a l w i th the fundamental t o n e , whereas the o t h e r , hav ing a sharp tone q u a l i t y and g r e a t l o u d n e s s , was of d i f f e r e n t o r i g i n . By e l i m i n a t i n g harmonics one by one, s t a r t i n g from the l owes t , Schouten found t h a t the sharp n o t e , a t f i r s t , d i d not change e i t h e r i n c h a r a c t e r or i n l o u d n e s s . There was, however, a g r a d u a l l o s s i n both sharpness and loudness of the sharp note when the h i g h e s t harmonics were removed f i r s t . From these r e s u l t s , he suggested tha t the sharp note i s a s s o c i a t e d wi th the presence of h igh harmonics i n the complex sound, and thereby conf i rmed Seebeck's o r i g i n a l f i n d i n g . T h i s a d d i t i o n a l s u b j e c t i v e component whose e x i s t e n c e c o u l d not be c o r r e l a t e d wi th any s i n g l e fequency of the sound, but which i s , a c c o r d i n g to Schouten (1940c) , a c o l l e c t i v e m a n i f e s t a t i o n of u n r e s o l v e d h igher harmonics was c a l l e d a " r e s i d u e " . Schouten (1940c) next determined which p h y s i c a l 4 property of these higher harmonics might determine the pitch of the residue: the distance between the harmonics or the p e r i o d i c i t y of the t o t a l waveform of the harmonics were scrut i n i z e d . Comparing two waveforms having the same distance of 400 Hz between the harmonics but a d i f f e r e n t p e r i o d i c i t y (200 Hz and 400 Hz), he found that the residue pitch in each of the waveforms had a frequency value equal to that of the p e r i o d i c i t y , namely 200 and 400 Hz. Hence, Schouten concluded that the ear assigns a pitch to a residue by virtue of the p e r i o d i c i t y . However, in one of Schouten's most c r u c i a l experiments (Schouten,1940a), i t was established that the s i t u a t i o n was not as simple as was f i r s t assumed. By s h i f t i n g a set of harmonics c o l l e c t i v e l y over a small distance along the frequency scale, the pitch of the residue shifted in proportion to the change in the constituent frequencies. Not only do these results imply that the pitch is not determined by the spacing of the harmonics since t h i s remained constant, but they also imply that the envelope  per iod ic i t y is unrelated since this also remains unchanged following the s h i f t of components (Schouten,1970). Consequently, Schouten believes that the f ine t ime structure of the waveform must be taken into account, since i t is this property that is altered following the pitch s h i f t (Schouten et al.,1962). Pitch frequency would therefore be given by 5 t h e i n v e r s e o£ t h e t i m e b e t w e e n t h e m a j o r p o s i t i v e p e a k s i n t h e s t i m u l u s f i n e s t r u c t u r e . From t h e ' t i m e ' f o l l o w i n g S c h o u t e n ' s f i n d i n g s up u n t i l t h e e a r l y 1 9 7 0 ' s 7 t h e r e was a ' s h i f t ' i n t h e r e l a t i v e w e i g h t a f f o r d e d t o p l a c e and t i m i n g m e c h a n i s m s . I t was d u r i n g t h i s ' p e r i o d ' t h a t t h e e m p h a s i s was ' p l a c e d ' on t h e t i m i n g o f n e u r a l d i s c h a r g e s , r a t h e r t h a n t h e l o c a t i o n o f i n n e r v a t i o n o f e x c i t e d n e u r o n s . As e a r l y a s t h e m i d - s i x t i e s i t was d e m o n s t r a t e d t h a t t h e m a j o r i t y o f c o c h l e a r f i b e r s have a r e s t r i c t e d d y n a m i c r a n g e b e t w e e n 20 and 50 dB ( K i a n g e t a l . , 1 9 6 5 ; K i a n g , 1 9 6 8 ; E v a n s , 1 9 7 2 ) . F o r l e v e l s above t h i s r a n g e , t h e d i s c h a r g e r a t e s i n t h e f i b e r s w i l l be s a t u r a t e d f o r s i g n a l s a t t h e c h a r a c t e r i s t i c f r e q u e n c y o f t h o s e f i b e r s . P s y c h o p h y s i c a l s t u d i e s h a v e , h o w e v e r , r e v e a l e d t h a t o u r p e r c e p t u a l d y n a m i c r a n g e e n a b l e s us t o h e a r and a n a l y s e c o m p l e x s o u n d s o v e r 100 dB o r more ( R i e s z , 1 9 2 8 ; M i l l e r , 1947 ) . T h i s p r e s e n t e d a s e r i o u s p r o b l e m f o r p l a c e c o d i n g , s i n c e t h e f r e q u e n c y r a n g e o v e r w h i c h c o c h l e a r f i b e r s a r e s a t u r a t e d by l o u d t o n e s c a n be v e r y e x t e n s i v e ( E v a n s , 1 9 7 8 b ) . F i b e r s w i t h l o w b a c k g r o u n d r a t e s , h i g h t h r e s h o l d s , and w i d e d y n a m i c r a n g e s , h o w e v e r , have been d e s c r i b e d ( L i b e r m a n , 1 9 7 8 ; L i b e r m a n & K i a n g , 1 9 7 8 ) . I t i s t h u s c o n c e i v a b l e t h a t d i f f e r e n t f i b e r s f r o m t h e same b a s i l a r membrane l o c a t i o n c o u l d e x p l a i n p u r e t o n e p i t c h on t h e b a s i s o f t h e p l a c e t h e o r y , a l t h o u g h t h e r e i s , s o f a r , no p r o o f f o r 6 t h i s p o s s i b i l i t y . S e v e r a l i n v e s t i g a t o r s suggest t h a t c o c h l e a r f i b e r s t r a n s m i t i n f o r m a t i o n i n terms of the f i n e time s t r u c t u r e of t h e i r d i s charge p a t t e r n s ( G o l d s t e i n & S r u l o v i c z , 1 9 7 7 ; Evans,1977,1978b). For frequency s i g n a l s below 5 kHz, c o c h l e a r nerve f i r i n g s have a tendency to occur at a p a r t i c u l a r phase of the s t i m u l a t i n g waveform, and the dynamic range over which t h i s 'phase l o c k i n g ' occurs extends w e l l beyond that of the mean dis c h a r g e r a t e (Rose et al.,1971). In the e a r l y 1970's, the emphasis on p i t c h p e r c e p t i o n moved from p e r i o d i c i t y coding, to t h e o r i e s based upon p a t t e r n r e c o g n i t i o n models (Terhardt,1972,1974; Goldstein,1973; Wightman,1973). These models i n v o l v e a c e n t r a l n e u r a l processor which computes the p i t c h of complex sounds i n the f o l l o w i n g manner. Resolved frequency components of the complex sound, which have been analysed i n the p e r i p h e r y , provide the p i t c h cues. In most models t h i s i n f o r m a t i o n i s conveyed by place mechanisms. Upon r e c e i v i n g t h i s i n f o r m a t i o n , the c e n t r a l n e u r a l processor matches these frequency components to a harmonic s e r i e s . The fundamental frequency of those harmonics which best f i t s the r e s o l v e d components w i l l then be s e l e c t e d by the c e n t r a l processor as the p i t c h value (Evans,1978b). The major d i f f e r e n c e between p a t t e r n r e c o g n i t i o n models 7 a n d S c h o u t e n ' s m o d e l f o r t h e r e s i d u e p i t c h i s t h a t t h e p a t t e r n r e c o g n i t i o n m o d e l s r e q u i r e s p e c t r a l r e s o l u t i o n o f i n d i v i d u a l c o m p o n e n t s i n t h e s t i m u l u s , w h e r e a s S c h o u t e n ' s t e m p o r a l m o d e l r e q u i r e s i n t e r a c t i o n o f c o m p o n e n t s . F u r t h e r m o r e , a c c o r d i n g t o S c h o u t e n ' s m o d e l , t h e p i t c h o f t h e r e s i d u e may s t i l l be h e a r d when t h e r e a r e no r e s o l v e d p a r t i a l s . I n 1972, H o u t s m a & G o l d s t e i n p r o v i d e d p e r h a p s t h e m o s t c o n v i n c i n g e v i d e n c e d e m o n s t r a t i n g t h a t t h e l a c k i n g f u n d a m e n t a l c a n be p e r c e i v e d when t h e r e i s no p o s s i b l e i n t e r a c t i o n o f p a r t i a l s i n t h e c o c h l e a . T h e i r e x p e r i m e n t i n v o l v e d p r e s e n t i n g a s u b j e c t w i t h a m u s i c a l m e s s a g e c o n s i s t i n g o f two n o t e s , e a c h n o t e c o m p r i s e d o f two r a n d o m l y c h o s e n s u c c e s s i v e u p p e r h a r m o n i c s , b u t w i t h no e n e r g y a t t h e f u n d a m e n t a l f r e q u e n c y i t s e l f . T h e s u b j e c t s were a s k e d t o i d e n t i f y t h e t w o - n o t e m e l o d i e s w h i c h were p r e s e n t e d m o n o t i c a l l y (two h a r m o n i c s t o one e a r ) a n d d i c h o t i c a l l y (one h a r m o n i c t o e a c h e a r ) . S u b j e c t s c o u l d r e c o g n i z e m e l o d i e s e q u a l l y w e l l w i t h b o t h m e t h o d s o f s t i m u l u s p r e s e n t a t i o n . T h i s s u g g e s t s t h a t f u n d a m e n t a l s o f c o m p l e x t o n e s t i m u l i a r e s e l e c t e d b y a c e n t r a l m e c h a n i s m w h i c h i n t e g r a t e s a n d p r o c e s s e s t h e r e s o l v e d s t i m u l u s h a r m o n i c s f r o m b o t h c o c h l e a e . S c h o u t e n ' s t e m p o r a l m o d e l e x p l a i n i n g t h e r e s i d u e p i t c h b y i n t e r a c t i n g p a r t i a l s i s s u p p o r t e d b y t h e work o f R i t s m a 8 (1962,1963) who defined the existence region of the tonal residue. His subjects were required to indicate whether they could perceive a residue in response to complexes consisting of three consecutive harmonics. He found that the residue pitch could be heard even when the harmonic numbers of p a r t i a l s were around 20. Plomp (1964) had shown that for complex tones with more than two components, only the f i r s t five to eight harmonics are resolved. Consequently, Ritsma showed that the residue can be perceived even when no individual p a r t i a l s of a complex tone are separately perceivable. Furthermore, he found that no tonal residue is perceived when component frequencies are higher than 5000 Hz. Since this value is also the l i m i t of neural phase locking, temporal mechanisms cannot operate beyond i t . Thus, our a b i l i t y to perceive the tonal residue of a complex tone only occurs when p a r t i a l s are present in a frequency region which allows phase-locking of auditory f i b e r s . Rltsma's experiments were not e n t i r e l y conclusive since he did not control for the possible influence of combination tones. Combination tones often have frequencies of the fundamental or low components, and the type 2 f l - f 2 may be i n d i v i d u a l l y perceivable even though the stimulus components are unresolved. To control for combination tones, Moore (1973) conducted an experiment in which a multi-tone complex 9 with no resolvable p a r t i a l s was presented to subjects In the presence of a masking noise in the frequency region below the complex. Results indicated that the subjects heard a well-defined residue pitch, thus confirming Ritsma's conclusions. Moore & Rosen (1979) have also provided more recent evidence supporting temporal coding of the residue pitch by testing subjects on their a b i l i t y to recognize melodies from which rhythm information had been removed. The purpose of th i s test was to determine whether residue pitch produced by unresolvable high harmonics was of a musical value. To mask combination tones, low frequency noise was, again, present. The subjects were able to i d e n t i f y simple tunes from the musical i n t e r v a l information. Thus, a sense of musical pitch was maintained with stimuli containing only harmonics too high to be i n d i v i d u a l l y analysed in the peripheral auditory system. In the studies reviewed thus far, evidence was presented for pitch coding on the basis of either resolved p a r t i a l s (pattern recognition models) or interacting p a r t i a l s (temporal models) as i f one hypothesis excluded the other. However both place and temporal cues may be used by the central nervous system. This p o s s i b i l i t y was f i r s t explored for coding of vowels (which are also harmonically structured sounds) by Young & Sachs (1979), and later was 10 extended to non-harmonic speech sounds, e.g., stop consonants, by M i l l e r & Sachs (1983). These authors explored the representation of complex speech sounds in the entire population of the cat's auditory nerve f i b e r s . If only the spike rates were used to express amplitudes for various frequencies at the c h a r a c t e r i s t i c locations along the b a s i l a r membrane, i t was not possible to r e l i a b l y d i s t i n g u i s h d i f f e r e n t sounds (e.g., the vowels |e| and |a|). If the amplitudes were expressed, however, as the degree to which fibers synchronize with frequency components (by phase-locking), c h a r a c t e r i s t i c patterns emerged for each sound. The synchronization measure employed by Young and collaborators was the "synchronization index" introduced by Goldberg & Brown (1969). This index has i t s maximal value close to a fiber' s c h a r a c t e r i s t i c frequency, which i s , of course, l o c a l i z e d on the basi l a r membrane. The measure for complex sound coding was, therefore, c a l l e d "average l o c a l i z e d synchronization rate" (ALSR), and was measured as follows. F i r s t , obtained is the amplitude of response of a stimulus component at that component frequency. Next, this amplitude is averaged across f i b e r s , but only those that are tuned within plus or minus 0.25 octaves of the frequency of the p a r t i a l . This mean amplitude is then taken to represent the ALSR of the stimulus component's population response. Accordingly, the ALSR contains information, regarding both 11 time and place, about the neural response to a frequency: Time because the average value of the amplitude measured is synchronized rate, and place because the fibers included in the averaging process are only those that are tuned near that frequency (Sachs,1984). M i l l e r & Sachs (1983) have shown that some pitch estimates can also be derived from ALSR measures with s u f f i c i e n t accuracy to permit tracking of small pitch changes. Again using responses of large populations of cat single auditory nerve fibers to consonant-vowel s t i m u l i , they also demonstrated l i t t l e or no representation of pitch based s o l e l y upon the temporal structure of the stimulus waveform, as measured by the envelope modulation of the post-stimulus time histograms (Miller & Sachs,1984). The envelope modulations d i r e c t l y related to pitch period were shown only in those units with c h a r a c t e r i s t i c frequencies in ranges where there are a number of pitch harmonics with approximately equal amplitude. M i l l e r & Sachs (1984) believe that this was a res u l t of r e c t i f i e r d i s t o r t i o n contributed by pairs of response peaks. Units whose responses were dominated by a single component showed no such pitch-related fluctuations in their post stimulus time histograms. However, the pitch-related harmonic structure in the stimulus spectrum was preserved by the ALSR, a representation of pitch based upon both the temporal 12 a u d i t o r y - n e r v e responses and the co c h l e a r p l a c e . T h i s f i n d i n g has s i n c e been r e p l i c a t e d i n the guinea p i g (Palmer et a l .,1986). Experiments on the e f f e c t of noise on the s y n c h r o n i c i t y of d i s c h a r g e s r e v e a l e d some very i n t e r e s t i n g f a c t s . Kiang & Moxon i n 1974 recorded from s i n g l e u n i t s i n the a u d i t o r y nerve of the a n e s t h e t i z e d c a t , and showed that low-frequency masking noise s c a r c e l y a f f e c t e d the synchrony of low c h a r a c t e r i s t i c frequency u n i t s i n respone to phonetic elements, even though the noise l e v e l was s u f f i c i e n t to s a t u r a t e the di s c h a r g e r a t e of most of these u n i t s . On the other hand, f o r high c h a r a c t e r i s t i c frequency u n i t s , a r e d u c t i o n i n synchrony was found even at masking l e v e l s too low to s a t u r a t e these f i b e r s . S i m i l a r f i n d i n g s have been r e p o r t e d by Rhode et a l . (1978) while r e c o r d i n g from s q u i r r e l monkey a u d i t o r y nerve f i b e r s . Narrow bands of noise centered around the c h a r a c t e r i s t i c frequency of low c h a r a c t e r i s t i c frequency f i b e r s r e s u l t e d i n f l a t r a t e curves above 40 dB SPL, whereas s y n c h r o n i z a t i o n was maintained. Furthermore, they even showed that a neuron which e x h i b i t e d no response to pure tones with i n t e n s i t i e s l e s s than 50 dB SPL achieved a h i g h l y s i g n i f i c a n t degree of s y n c h r o n i z a t i o n when a low i n t e n s i t y noise was presented together with the tone at 40 dB SPL. Rhode et a l . suggest that t h i s l a t t e r f i n d i n g was the r e s u l t 13 o£ the a b i l i t y o£ the noise to increase the p r o b a b i l i t y of the neuron's stimulus-induced potential to cross f i r i n g threshold under stimulus conditions that would normally not permit such crossings to occur. They draw an analogy to auditory neurons with low and high spontaneous.activity, the l a t t e r being more sensitive to tonal s t i m u l i . Delgutte (1980) also showed that although the r e l a t i v e rate response to a tone was decreased in the presence of noise in cat auditory f i b e r s , the synchronization index remained approximately the same throughout the duration of a tone burst, both in the presence and absence of noise. Furthermore, because noise did not a f f e c t the intervals between the spectral peaks of the response pattern to speech sounds, Delgutte concluded that the information about formant frequencies of vowels remained r e l a t i v e l y stable in a noisy background. Similar findings have been obtained by Abbas (1981) and Voigt et a l . (1981). In a further investigation, Sachs et a l . (1983) found that addition of background noise to a steady-state vowel suppressed the synchronized responses to the formants in high c h a r a c t e r i s t i c frequency f i b e r s , but only s l i g h t l y reduced the synchrony to the formant frequencies at their peculiar low frequency place in the neural population. More recently, M i l l e r et a l . (1987) obtained responses from anesthetized cat auditory nerve fibers to both a 1.0 14 kHz tone, and 1.0 kHz tone in background noise. Addition of the broadband noise resulted in maintainence of the synchrony only in those units with c h a r a c t e r i s t i c frequencies close to the 1.0 kHz stimulus, whereas phase-locking was lost in those auditory nerve fibers with c h a r a c t e r i s t i c frequencies far from the 1.0 kHz stimulus. Similar findings have also been reported by Delgutte & Kiang (1984) and by M i l l e r (1986). Rationale The persistence of a high synchronization index in neural discharges of low frequency fibers during presentation of a low frequency masking noise makes i t necessary to re-evaluate the significance of the findings by Moore (1973) and Moore & Rosen (1979). To r e c a l l , these two studies examined the potential of stimuli containing only high, unresolved harmonics to evoke the percept of the residue pitch . Low frequency masking noise was used to eliminate any contribution of d i s t o r t i o n products to the percept. But how e f f e c t i v e was this masking noise in eliminating a l l the pitch cues relayed by the low c h a r a c t e r i s t i c frequency fibers? Information represented by discharges synchronized to the acoustic waveform would s t i l l be available to the central nervous system, information that might contain s u f f i c i e n t cues for the residue pitch . 15 Questions and speculations o£ this nature led to the design of the experiments presented here. U n t i l now, no experiment testing the c a p a b i l i t y of a group of harmonics to evoke the lacking fundamental, without contribution from pitch cues provided by the frequency region of the missing fundamental, has been reported. These questions can be addressed in patients with a complete sensorineural hearing loss in the low frequency region (the presumed place representation of the fundamental), and a completely intact organ of Corti in a higher frequency band (the proper place for dominant higher components). Since such sharply limited damage is not known in cochlear pathology, i t was attempted here to perform conclusive measurements in patients with more gradual p a r t i a l low-frequency losses. 16 METHODS A. Subjects Subjects a u d i o l o g i c a l l y diagnosed with u n i l a t e r a l , low frequency sensorineural hearing loss of cochlear o r i g i n ranging in age from 33 to 66 were used. Hearing loss of this o r i g i n is frequently associated with degenerative changes in the auditory nerve (Schuknecht,1974). Only six such patients could be found in the audiology c l i n i c s ' in Vancouver. Three patients (A.D., A.F., and L.F.) had Meniere's disease. This disease of unknown etiology is characterized by an abnormal accumulation of endolymph in the inner ear r e s u l t i n g in hearing loss, vertigo, and t i n n i t u s (Schuknecht,1974). Retrocochlear involvement was excluded in patient G.F. as a res u l t of normal auditory brainstem responses and normal acoustical reflexes. S i m i l a r l y , retrocochlear involvement was excluded in patient R.L. as a result of a positive S.I.S.I. (Short increment S e n s i t i v i t y Index) test, and in patient J.W. as a result of intact acoustical reflexes and excellent speech discrimination. Pathological subjects were used in the study of a normal phenomenon since they could not hear low pure tones, and therefore perception of a low pitch of a complex tone by these patients would confirm the u t i l i z a t i o n of a central pitch process. The decrease in threshold with 17 increasing frequency in the patients' impaired ears ranged from 22.0 dB to 36.0 dB (refer to figures 1 and 2, and to table 2 in "r e s u l t s " for the audiograms and for the frequency ranges over which the thresholds decreased). A l l were paid for their services, and were instructed in frequency discrimination prior to testing. Two of the subjects (L.F. and R.L.) had previous musical t r a i n i n g . B. Stimuli In order to measure perceived pitches, patients had to compare test tones to comparison tones. Test sounds consisted of harmonic series with component i n t e n s i t i e s set to the same SL l e v e l s . They were j o i n t l y varied during presentations from 20 to 30 dB SL in order to circumvent errors due to intensity cues. The series contained harmonic numbers three to ten maximally with the fundamental and second harmonic being absent. The choice of harmonics as well as the frequency value of the missing fundamental depended upon the individual hearing loss of each patient as described below. The comparison tone was of a single sinusoid also presented at randomized i n t e n s i t i e s , again ranging from 20 to 30 dB SL. A l l tones were 500 ms long and had r i s e and f a l l times of 10 ms. A l l stimuli were generated by a d i g i t a l synthesizer 18 capable of producing up to 32 pure tone components at any frequency and amplitude. Frequencies and amplitudes of the components were controlled by a LSI 11-23+ computer system. C. P r o c e d u r e Pure Tone Audiogram Prior to the experiments, pure tone audiograms were obtained for a l l patients. Sinusoidal frequencies of 125, 250, 500, 1000, 2000, 4000, and 8000 Hz were presented randomly via Sennheiser HD414X headphones, which had been calibrated with a Hewlett Packard HP3582A spectrum analyser in conjunction with a Bruel & Kjaer 4134 1/2-inch condenser microphone, and a 2619 microphone preamplifier using a 2804 microphone power supply. S i t t i n g in a sound attenuating room, patients were presented with one of the pure tones at 30 dB above "hearing l e v e l " as determined from the most recent c l i n i c a l audiograms obtained at audiology c l i n i c s in Vancouver. Subjects were instructed to push a button within 10 to 1500 msec after the onset of the tone. If the response was made within this time period, the intensity was reduced one step ( i n i t i a l stepsize: 8 dB), and another 500 msec tone of the same frequency was presented at th i s lower intensity l e v e l 3 sec following the response. 19 If no response was made within the 1490 msec response window at a par t i c u l a r i n t e n s i t y l e v e l , the tone was repeated at the same intensity 3 sec l a t e r . After two consecutive tones without a response, the intensity increased by one step, up to a l i m i t i n g intensity level of 80 dB SPL, u n t i l an appropriate response was executed. After three "crossovers" (an int e n s i t y increase/decrease or vice versa), the stepsize was reduced to one-half of i t s previous value (e.g., from 8 dB to 4 dB). When the stepsize equalled 0.5 dB, the sequence for a pa r t i c u l a r tone was terminated. Audiograms were then obtained by averaging the int e n s i t y of the la s t three i n t e n s i t i e s for each tone. Frequency sequences were randomized and the entire procedure automatized. Thresholds for intermediate frequencies were defined by linear interpolation and used to set SL levels of stimuli employed for pitch matching. Pitch Training Prior to the pitch matching experiments, each subject was asked to i d e n t i f y whether two sequentially presented i d e n t i c a l melodies were similar or d i f f e r e n t in pitch. Each melody consisted of five notes played on a Yamaha DX-7 programmable synthesizer and presented to the patient's intact ear. Corresponding notes of the two melodies d i f f e r e d in either pitch or timbre (overtone structure). 20 When d i f f e r i n g in pitch, melodies were transposed by a musical fourth or a f i f t h (e.g., the "G" above and below the "C"). When d i f f e r i n g in timbre, corresponding notes d i f f e r e d in the number of harmonic components present. Six choices were available; a pure tone, or a complex consisting of harmonics one to si x , two to seven, three to eight, four to nine, or five to ten. Patients were trained u n t i l they could comfortably and c o r r e c t l y i d e n t i f y a s i m i l a r i t y or difference in pitch between several paired melodies. Pitch Matching of Complex Tones Using a  Two-Alternative Forced Choice Adaptive Method Complex tones were presented to patients with low frequency hearing loss in order to investigate the relati o n s h i p between cochlear damage and the a b i l i t y to perceive the lacking fundamental. The test sound's components were chosen in accordance with the patients' audiograms such that harmonic components would f a l l within a frequency range with r e l a t i v e l y normal thresholds, whereas the (lacking) fundamental would occupy a region with elevated thresholds. Harmonics chosen were the t h i r d to the tenth ( i . e . , eight components), except for two patients the eighth to the tenth harmonics were omitted since their frequencies would correspond to a second range with threshold elevations. The second harmonic was Intentionally 21 excluded from the complex in order to avoid octave confusions (Deutsch,1974a,b,1975). Duration of complex and pure tones was 500 msec separated by a s i l e n t i n t e r v a l of 400 msec. Both the complex test sound and the comparison pure tone were presented via headphones using the following procedures: i) Pitch matching control. Both sounds were presented to the patient's intact ear using threshold data from that ear to set the component i n t e n s i t i e s . This was necessary to permit comparison of pitch estimates by means of healthly and damaged ears in the same subjects. i i ) Pitch matching control with low-pass f i l t e r e d noise. As in i) but with low-pass f i l t e r e d noise, sloping at 9G dB/octave, added to the complex test sound in order to mask only the region representing the fundamental, but not the frequency area containing the presented p a r t i a l s . Corner frequencies (3 dB attenuation) were logarithmically centered between the fundamental and the t h i r d harmonic. Noise was f i l t e r e d by a Krohn-Hite 3343 Butterworth f i l t e r . The masked threshold for a pure tone at the frequency of the fundamental was determined for the intact ear. The pure tone intensity was fixed at 30 dB SL (the maximum 22 intensity l e v e l for any one component presented in the experiments), and the in t e n s i t y of the noise was increased u n t i l the patient could no longer perceive the tone. The r e s u l t i n g signal to noise r a t i o averaged -0.9 dB, and ranged from -9.7 dB to +10.2 dB. This wide range was a result of the varying noise band width, which was adjusted to match the hearing loss in the damaged ear (Fletcher,1940; Zwicker,1954; Patterson,1976). i i i ) Pitch matching between ears. The complex test sound was presented to the damaged ear only. This was alternated with the comparison tone presented only to the functional ear. Threshold data from the patient's intact ear were used to set the in t e n s i t y of the pure tone, whereas the threshold data from the damaged ear served to set the component i n t e n s i t i e s of the complex sound. Since components of the complex f e l l within the intact frequency range of the damaged ear, and the missing fundamental within the damaged frequency area, a contribution to the percept of the lacking fundamental by d i s t o r t i o n products generated in the cochlea (Plomp,1965; Greenwood,1971; Hall,1972a,b; Smoorenburg,1972) would be highly unlik e l y at the i n t e n s i t i e s employed. iv) Pitch matching between ears with noise. As in i i i ) but with added low-pass f i l t e r e d noise presented together with the complex test sound as described in i i ) . 23 The low-pass f i l t e r e d masking noise was used as an additional safeguard against possible contamination by d i s t o r t i o n products. Determination of the noise masked threshold was. as described in i i ) with the exception of the pure tone and masking noise being presented to the damaged ear instead of the intact ear. The signal to noise r a t i o for the thresholds averaged +9.4 dB, and ranged from +3.4 dB to +12.6 dB. The 500 ms test tone was always followed by the 500 ms comparison tone. The subjects were required to push a yellow ("higher") button i f the sinusoid (2nd tone) was higher, and a blue ("lower") button i f i t was lower in pitch than the complex tone (1st tone), both within 10 to 3500 msec after the onset of the comparison tone. A two-alternative forced choice adaptive method (Levitt,1971; Jesteadt,1980) was used. In this procedure, the frequencies of stimuli in a given t r i a l were dependent upon the subject's responses in previous t r i a l s . If a response was made within the 3490 msec response window, a 3 sec delay followed between the response and the presentation of the f i r s t tone of the next t r i a l . If no response was made in the response window, the i d e n t i c a l two tones were repeated in the next t r i a l 3 sec following the termination of the response window. 2 4 Two randomly interleaved sequences ("A" and "B") of stimulus presentation were used for each subject. In sequence A, the frequency of the comparison tone (f2) was i n i t i a l l y equal to 1.5 times the fundamental frequency (flo) of the test sound. If f2 was judged to have a higher pitch than the test sound, then the same f2 was presented in the following t r i a l . If judged higher again, £2 decreased one stepsize (see table 1). If judged lower, f2 increased one step up. After three reversals (from up to down to up) the stepsize was reduced (e.g., from 1 to 2). Sequence A was terminated after the t h i r d reversal of the l a s t step s i z e . The subjective pitch of the complex stimulus for sequence A was taken as the mean of the last four values of f2. I f , however, two consecutive values were i d e n t i c a l , only one of them was used. The following example i l l u s t r a t e s f2 value selection for pitch c a l c u l a t i o n . £2 va lues presentation number - - > 3 0 0 (n - 5) 3 3 7 (n - 4) - - > 3 3 7 (n - 3 ) - - > 3 0 0 (n - 2) 3 3 7 (n - 1) - - > 3 3 7 (n) 25 T a h l f. 1 S t f t p s l g f t s f o r th*. n o m p a r 1 s o n p u r * t o n * ( f:2 ) When d e c r e a s i n g £2 S t e p s i z e 1: f2 - (f2 / 1.5) (maximal s t e p s i z e ) S t e p s i z e 2: f2 - (f2 / 1.25) S t e p s i z e 3: £2 - ( £ 2 / 1.125) (minimal s t e p s i z e ) When i n c r e a s i n g £2 S t e p s i z e 1: (f2 x 1.5) - f2 (maximal s t e p s i z e ) S t e p s i z e 2: ( £ 2 x 1.25) - f2 S t e p s i z e 3: (f2 x 1.125) - £2 (minimal s t e p s i z e ) * * * £2 = l a s t f requency va lue of comparison tone 26 The four values averaged to estimate the subjective pitch are those indicated by the arrows. The precision of this pitch estimate depends, of course, on the f i n a l step size which i s , in practice, well within the error range for most normal subjects. In sequence B, f2 i n i t i a l l y was set one maximal step below f l o . In t h i s sequence two consecutive lower responses were required to increase f2 by one stepsize, but only one higher response was necessary to decrease f.2 (the reverse of sequence A). As in sequence A, the stepsize was reduced after three reversals (from down to up to down). Termination of sequence B and ca l c u l a t i o n of the subjective pitch of the complex stimulus were as described for sequence A. Advantages of the two-alternative forced choice adaptive method (Jesteadt,1980) used in these experiments are: 1. The stimulus (f2) is automatically chosen at an appropriate degree of arduousness. As the subject improves his or her performance, the d i f f i c u l t y of the exercise increases. Thus, the patient's task is formatted to his needs . 2. By using two randomly interleaved sequences (phases A and B), the effects of d i r e c t i o n a l bias is reduced. 3. Since subjects can not influence the choice of 27 s t i m u l i , this procedure is r e l a t i v e l y objective when compared with adjustment techniques. Pitch Matching of Complex Tones Using an Up-Down Adjustment Technique Five of the six patients returned a week after p a r t i c i p a t i n g in the aforementioned pitch matching experiments. Pitch t r a i n i n g was again performed. Patients were then presented with the same complex test sound used in the previous pitch matching experiments followed by a pure tone of 100 or 1130 Hz. Complex tone fundamentals were always between these values. Patients were asked to adjust the frequency of the pure tone by turning a d i a l on a potentiometer connected to a voltage controlled o s c i l l a t o r (Coulbourn S24-05), the source of the second pure tone. The duration for each of the two tones was 500 ms with a s i l e n t i n t e r v a l of 200 ms. A 700 ms gap followed the end of the second tone before the f i r s t complex tone of the next group was started. Amplitude of the components of the complex was set at 30 dB SL by the LSI 11-23+ computer. The amplitude of the pure tone was also 30 dB SL, and adjusted by a Hewlett Packard 350D attenuator. Its frequency was monitored by a Hewlett Packard 5381A 80-MHz frequency counter. Patients were allowed unlimited time to adjust the pure 28 tone to match the complex, as groups of the two tones were presented repeatedly to the patients. The patients were also encouraged to make broad sweeps at f i r s t , adjusting the frequency above and below the pitch of the complex, and then gradually make finer adjustments to define the perceived pitch. The patients were required to adjust the pure tone, f i r s t from a s t a r t frequency (100 Hz) well below the complex tone fundamental and then, in a second run, from a higher st a r t frequency (1130 Hz) far above the fundamental. These alternating s t a r t frequencies eliminated the influence of frequency adjustment d i r e c t i o n on the pitch matching. The number of pitch matches each patient performed for each of the methods were as follows: mean number of matches range i) P.M. control : 7 4 - 1 0 i i ) P.M. control with noise : 6 4 - 1 0 i i i ) P.M. between ears : 8 4 - 1 5 iv) P.M. between ears with noise : 7 4 - 1 5 29 D_. S t a t i s t i c a l Analysis Results from the two-alternative forced choice routine are shown as mean plus or minus SEM. 30 RESULTS Pure Tone Audiograms Pure tone audiograms of the six patients' damaged (D) and intact (I) ears are displayed in figures 1 and 2. Thresholds are depicted in dB SPL and dB HL. The decrease in threshold with increasing frequency ranged from 22.0 to 36.0 dB (see table 2 for the frequency ranges). From these audiograms the complex tone frequency components were chosen such that they would f a l l within the intact portion of the patient's damaged ear, but whose lacking fundamental would f a l l within the damaged frequency range. The c r i t e r i o n given for an intact area was a threshold d e f i c i t at a pa r t i c u l a r frequency of no greater than 15 dB HL, while that given for a damaged area was 18 dB HL or greater. These c r i t e r i a were chosen following audiometric examination so as to conform with the selection of presented components within the intact frequency region, and the fundamental within the damaged area. Selection of components for each patient is shown in table 3. As mentioned in "methods", for a l l but two of the patients, eight components with harmonic numbers three to ten were chosen. For patients L.F. and R.L., the eighth to the tenth harmonic components were omitted since their frequencies would have occupied a high frequency range of threshold elevation. 31 Figure 1 ; Damaged ear ( s o l i d line) and intact ear (dashed line) audiograms of patients A.D./ A.F., and G.F. Thresholds are displayed in dB HL. Solid bars = range of i n t e n s i t i e s of the presented stimulus components during the two-alternative forced choice adaptive method. Dashed bar = range of in t e n s i t y of the comparison pure tone at the fundamental frequency during the two-alternative forced choice adaptive method. F l = fundamental frequency of the presented complex tone. 32 -20-, -10-P-10-20-m 4°-l "D 50 60-70 80H 90 100 -20-, -10-0-10-20-=J 30-§ 50-60-70-80 90 100-1 P a t i e n t : A . D . F = 300 125 250 500 1K 2K 4K 8K P a t i e n t : A . F . F1 = 200 125 250 500 IK 2K 4K 8K - 1 0 0 10-20--J 30-40-Sl 5°-; 60-70-80-90-100 P a t i e n t : G . F . F, = 200 125 250 500 1K 2K 4K 8K 33 Figure 2: Damaged ear ( s o l i d line) and intact ear (dashed line) audiograms of patients L.F., R.L., and J . W . Thresholds are displayed in dB HL. Solid bars = range of i n t e n s i t i e s of the presented stimulus components during the two-alternative forced choice adaptive method. Dashed bar = range of in t e n s i t y of the comparison pure tone at the fundamental frequency during the two-alternative forced choice adaptive method. F l = fundamental frequency of the presented complex tone. 34 -20-| -ioH "O 50-60-70-125 250 500 1K 2K 4K 8K 35 Table 2: Decrease in threshold with increasing frequency for each patient. patient decrease in threshold with increasing frequency (dB) frequency range (Hz) A.D. A.F. G.F. L .F. R.L. J . W . 26.0 26.0 32 . 0 24.0 22.0 36.0 250 250 125 125 125 500 1000 2000 500 1000 1000 2000 36 Table 3: Selection of components for the complex test sound used in the pitch matching experiments. patient components harmonic fundamental frequency  selected number of complex (Hz) (Hz) A.D. 900 3 300 A.F. 600 3 200 G.F. 1200 4 1500 5 1800 6 2100 7 2400 8 2700 9 3000 10 800 4 1000 5 1200 6 1400 7 1600 8 1800 9 2000 10 900 3 1200 4 1500 5 1800 6 2100 7 2100 3 2800 4 3500 5 4200 6 4900 7 5600 8 6300 9 7000 10 L.F. 300 R.L. J.W. 700 37 Pitch Matching of Complex Tones Using a Two-Alternative  Forced Choice Adaptive Method Results of the pitch matching between the complex and pure tones using the two-alternative forced choice adaptive method are shown graphically in figures 3 to 26. The pitch values from the various procedures are shown in tables 4 to 9. The values were calculated as described in the methods. Also shown are frequency values representing either the fundamental, i t s harmonic components, or octaves below harmonics, which best approximate the pitch values. The range of values used to establish a match to either of these was calculated as follows: The lower l i m i t was taken as the precise value to which the obtained value was approximated divided by the la s t stepsize (1.125). The upper l i m i t was logarithmically the same distance away from the precise value as was the lower l i m i t . Since the precision to which the fundamental is matched depends upon the f i n a l stepsize, a range of frequencies, rather than one frequency at the fundamental, must be considered an exact match. This is presented below each table. For example, figure 15 shows that patient L.F. c o r r e c t l y made the right responses in matching to a 300 Hz fundamental. However, because two of the four values used in the ca l c u l a t i o n of the pitch were either one f i n a l stepsize above or below the fundamental, the frequency range 38 Figure 3; Pitch matching control for patient A.D. using a two-alternative forced choice adaptive method. Both the complex and pure tones were presented to the intact ear. The straight lines represent the harmonic components of the complex test sound ( f l ) , i . e . , harmonics 3 - 1 0 . The graphic plots represent the frequency of the pure tone (f2) in r e l a t i o n to the component frequencies on a logarithmic scale. The upper plot is sequence A, the lower plot is sequence B. Plots were dependent on the patient's response after each presentation. On the righ t , actual frequency values (Hz) of the pure tone for each presentation ( f i r s t column) are depicted for sequence A (second column) and sequence B (third column). 39 161 6 e 1 . 0 0 0.E5 3000 Hx N  900 Hz i i i i i i i i i i i i I II i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i 0 £ H 6 6 10 1£ I T 16 18 £0 eg £ 7 £6 £8 30 3£ 3t 36 38 ^ 0 T £ Vt T6 T6 50 PRESENTATION PhTIENTi A . D . FUNDAMENTAL•300 Hz Fund 300 Hz SEGA SEQB 1 > 450 200 2) 450 300 3) 675 200 4> 675 133 5) 450 133 6) 675 199 7) 675 159 8) 450 159 9) 562 159 10) 562 127 11) 450 101 12) 562 89 13) 562 79 14) 450 79 15) 562 79 16) 562 89 17) 450 89 18) 506 0 19) 506 0 20) 450 0 21) 506 0 22) 506 0 23) 450 0 F i g u r e 4: P i t c h matching c o n t r o l with noise f o r p a t i e n t A.D. using a t w o - a l t e r n a t i v e f o r c e d choice adaptive method.. Both the complex and pure tones were presented to the i n t a c t ear. The s t r a i g h t l i n e s r e p r e s e n t the harmonic components of the complex t e s t sound ( f l ) , i . e . , harmonics 3 - 10. The gr a p h i c p l o t s r e p r e s e n t the frequency of the pure tone (f2) i n r e l a t i o n to the component f r e q u e n c i e s on a l o g a r i t h m i c s c a l e . The upper p l o t i s sequence A, the lower p l o t i s sequence B. P l o t s were dependent on the p a t i e n t ' s response a f t e r each p r e s e n t a t i o n . On the r i g h t , a c t u a l frequency values (Hz) of the pure tone f o r each p r e s e n t a t i o n ( f i r s t column) are d e p i c t e d f o r sequence A (second column) and sequence B ( t h i r d column). 41 161 e £ ' 1 . 0 0 3 0 0 0 H J N 900 H2 01 £5 I M I I I I I I M "1 I I I I I I U I I M "I I I | I I I I I I I I I I I I I I I I I I I I I I I 0 £ T 6 8 10 1£ i t 16 16 £0 £ £ £ T £6 £8 30 3£ 3T 36 38 7 0 Hfi 7 7 76 78 50 PRESENTATION PATIENT 1 A.D. FUNDAMENTAL!300 Hz Fund 300 Hz SEQA SEQB 1) 450 200 2) 450 300 3) 300 200 4) 300 133 5) 200 133 6) 300 199 7) 300 159 8) 450 127 9) 450 127 10) 300 101 11) 375 101 12) 375 126 13) 300 126 14) 300 158 15) 240 158 16) 300 140 17) 300 124 18) 240 124 19) 300 139 20) 300 123 21) 240 0 22) 270 0 23) 270 0 24) 240 0 25) 240 0 26) 213 0 27) 239 0 28) 239 0 29) 268 0 30) 268 0 31 ) 238 0 32) 238 0 33) 212 0 Figure 5: Pitch matching beween ears for patient A.D. using a two-alternative forced choice adaptive method. The complex tone was presented to the damaged ear, and the pure tone to the intact ear. The straight lines represent the harmonic components of the complex test sound ( f l ) , i . e . , harmonics 3 - 1 0 . The graphic plots represent the frequency of the pure tone (f2) in r e l a t i o n to the component frequencies on a logarithmic scale. The upper plot is sequence A, the lower plot is sequence B. Plots were dependent on the patient's response after each presentation. On the rig h t , actual frequency values (Hz) of the pure tone for each presentation ( f i r s t column) are depicted for sequence A (second column) and sequence B (third column). 43 16-e T e l . ( 3 . £ 5 3 3 0 ^ Ha i i i i i i i i i i i i i i i i i i i I i i i i n i i i I I i i i i i i i i i i i i i i i i i i i i £ f 6 8 10 i £ I T 16 16 £ 0 £ £ £ T £ 6 £ 6 3 0 3 £ 3 T 36 3 6 70 4 £ 7 7 7 6 HQ 5& P R E S E N T A T I O N P A T I E N T i A.D. F U N D A M E N T A L i 3 0 0 H z Fund 300 Hz SEOA SEOB 1) 450 200 2) 675 300 3) 675 300 4) 450 450 5) 675 300 6) 675 200 7) 450 200 8) 562' 300 9) 562 300 10) 450 239 11) 562 191 12) 562 191 13) 450 239 14) 562 191 15) 562 169 16) 450 169 17) 506 190 18) 506 190 19) 450 214 20) 506 214 21) 506 241 22) 569 214 23) 569 190 Figure 6: Pitch matching beween ears with noise for patient A.D. using a two-alternative forced choice adaptive method. The complex tone was presented to the damaged ear, and the pure tone to the intact ear. The straight lines represent the harmonic components of the complex test sound ( f l ) , i . e . , harmonics 3 - 1 0 . The graphic plots represent the frequency of the pure tone (f2) in r e l a t i o n to the component frequencies on a logarithmic scale. The upper plot is sequence A, the lower plot is sequence B. Plots were dependent on the patient's response after each presentation. On the r i g h t , actual frequency values (Hz) of the pure tone for each presentation ( f i r s t column) are depicted for sequence A (second column) and sequence B (third column). 45 1 6 -£' 1,00' 0 . e s •3000 Hs 5 0 0 H z i i i i i i i i i i i i i i i i i i i i i i i "i -i i i i i i i i -i i i i i i i i i i i i i i i i i i 0 £ T 6 8 10 i£ 17 16 16 £ 0 £ £ £ 7 £ 6 £8 3 0 3 £ 3 4 3 6 3 8 70 H £ V t 76 76 5 0 P R E S E N T A T I O N , , P A T I E N T 1 A.D. F U N D A M E N T A L 1 3 0 0 H z Fund 300 H; SEOA SEQB 1) 450 200 2) 450 200 3) 300 300 4) 450 200 5) 450 200 6) 675 200 7) 675 300 8) 450 200 9) 562 200 10) 562 300 1 1 ) 450 239 12) 450 191 13) 562 191 14) 562 239 15) 702 239 16) 702 299 17) 562 239 18) 562 239 19) 632 299 20) 711 .265 21 ) 799 235 22) 799 0 23) 710 0 Figure 7: Pitch matching control for patient A.F. using a two-alternative forced choice adaptive method. Both the complex and pure tones were presented to the intact ear. The straight l i n e s represent the harmonic components of the complex test sound ( f l ) , i . e . , harmonics 3 - 10. The graphic plots represent the frequency of the pure tone (f2) in r e l a t i o n to the component frequencies on a logarithmic scale. The upper plot is sequence A, the lower plot is sequence B. Plots were dependent on the patient's response after each presentation. On the r i g h t , actual frequency values (Hz) of the pure tone for each presentation ( f i r s t column) are depicted for sequence A (second column) and sequence B (third column). 47 16" 6" H £' 1.00' 0.E5 £ 0 0 0 Hr 600 Hz i i i i i i i i i i i i i i i i i i i i r- i i i i i i i i i i i i i i i i i r i i i i i r i i i i i 0 £ T 6 8 10 t£ I T 16 16 £0 ££ £ 7 £6 £8 30 3£ 3t 36 36 ^ 0 t£ Vt t6 H8 50 PRESENTATION PhTIENH A . F . FUNDAMENTAL.!£00 Hz Fund : 200 Hz SEQA SEOB 1) 300 133 2) 300 199 3) 200 199 4) 300 298 5) 300 198 6) 200 198 7) 300 297 8) 300 198 9) 200 198 10) 250 297 1 1 ) 312 237 12) 312 237 13) 250 296 14) 312 236 15) 312 236 16) 250 295 17) 281 235 18) 316 235 19) 316 294 20) 281 261 21 ) 316 261 22) 316 294 23) 0 261 24) 0 261 25) 0 294 26) 0 261 27) 0 261 Figure 8: Pitch matching control with noise for patient A.F. using a two-alternative forced choice adaptive method. Both the complex and pure tones were presented to the intact ear. The straight lines represent the harmonic components of the complex test sound ( f l ) , i . e . , harmonics 3 - 1 0 . The graphic plots represent the frequency of the pure tone (f2) in r e l a t i o n to the component frequencies on a logarithmic scale. The upper plot is sequence A, the lower plot is sequence B. Plots were dependent on the patient's response after each presentation. On the r i g h t , actual frequency values (Hz) of the pure tone for each presentation ( f i r s t column) are depicted for sequence A (second column) and sequence B (third column). 49 16" 8 e 1 . 0 0 1 0.85 £ 0 0 0 Hx 600 Hz i i i i i i i i i i i i i i i i i i" i i i i i i i I i I i I i i i i I I i I i i r i i i i i i i i i 0 £ 4 6 8 10 IS IT 16 18 £0 £8 £4 £6 £8 90 3£ 34 36 38 40 4£ 44 46 48 50 PRESENTATION PATIENT i A . F . FUNDAMENTAL«£00 Hz Fund 200 Hz SEQA SEOB 1) 300 133 2) 300 133 3) 200 199 4) 300 199 5) 300 298 6) 200 198 7) 300 198 8) 300 297 9) 200 198 10) 250 198 11 ) 312 297 12) 312 237 13) 250 237 14) 312 296 15) 312 236 16) 250 236 17) 281 295 18) 281 235 19) 250 235 20) 281 294 21 ) 281 261 22) 250 261 23) 281 294 24) 281 261 25) 0 261 26) 0 294 27) 0 261 28) 0 261 Figure 9: Pitch matching between ears for patient A.F. using a two-alternative forced choice adaptive method. The complex tone was presented to the damaged ear, and the pure tone to the intact ear. The straight lines represent the harmonic components of the complex test sound ( f l ) , i . e . , harmonics 3 - 10. The graphic plots represent the frequency of the pure tone (f2) in r e l a t i o n to the component frequencies on a logarithmic scale. The upper plot is sequence A, the lower plot is sequence B. Plots were dependent on the patient's response after each presentation. On the r i g h t , actual frequency values (Hz) of the pure tone for each presentation ( f i r s t column) are depicted for sequence A (second column) and sequence B (third column). 51 161 £000 H J \ 600 Hz 6" V £' 1 . 0 0 1 0i £51 i i i i i i i i i i i i i i i i i f i i i i ' i i i i T i i i i i i i i i i i i i i i i i i i i i i i 0 £ H 6 8 10 1£ I T 16 18 £0 £ £ £ T £6 £8 3< PRESENTATION PATIENTi A . F . FUNDAMENTALi£00 Hz Fund 200 Hz SEQA SEOB 1 > 300 133 2) 300 199 3) 200 199 4) 300 298 5) 300 198 6) 200 198 7) 300 297 8> 300 198 9) 200 198 10) 250 297 1 1) 250 237 12) 312 237 13) 312 296 14) 250 236 15) 312 236 16) 312 295 17) 250 235 18) 281 235 19) 281 294 20) 250 261 21 ) 281 261 22) 281 294 23) 250 261 24) 281 261 25) 281 294 26) 0 261 27) 0 261 Figure 10: Pitch matching between ears with noise for patient A.F. using a two-alternative forced choice adaptive method. The complex tone was presented to the damaged ear, and the pure tone to the intact ear. The straight l i n e s represent the harmonic components of the complex test sound ( f l ) , i . e . , harmonics 3 - 1 0 . The graphic plots represent the frequency of the pure tone (f2) in r e l a t i o n to the component frequencies on a logarithmic scale. The upper plot is sequence A, the lower plot is sequence B. Plots were dependent on the patient's response after each presentation. On the r i g h t , actual frequency values (Hz) of the pure tone for each presentation ( f i r s t column) are depicted for sequence A (second column) and sequence B (third column). 53 16 e 4 e 1 . 0 0 0 . £ 5 2:300 Hr \ 00 Hz I I I I I I I I I I I I I I I I I I I I I I I I 1 I I I I I 1 I 1 I I I I I I I I I I I I I I I I I 0 2 4 6 6 10 1£ 14 16 18 £0 ££ £4 £6 £6 30 3£ 34 36 38 40 4£ 44 46 48 50 PRESENTATION PATIENT'A.F, FUNDAMENTAL•£00 Hz Fund 200 Hz SEOA SEOB 1) 300 133 2) 300 199 3) 200 199 4) 300 298 5) 300 198 6) 200 198 7) 300 297 8) 300 198 9) 200 198 10) 250 297 1 1 ) 312 237 12) 312 237 13) 250 296 14) 312 236 15) 312 236 16) 250 295 17) 281 235 18) 281 235 19) 250 294 20) 281 261 21 ) 281 261 22) 250 232 23) 281 232 24) 281 261 25) 0 232 26) 0 232 E l g u K e 11; Pitch matching control for patient G.F. using a two-alternative forced choice adaptive method. Both the complex and pure tones were presented to the intact ear. The straight lines represent the harmonic components of the complex test sound ( f l ) , i . e . , harmonics 3 - 10. The graphic plots represent the frequency of the pure tone (f2) in r e l a t i o n to the component frequencies on a logarithmic scale. The upper plot is sequence A, the lower plot is sequence B. Plots were dependent on the patient's response after each presentation. On the r i g h t , actual frequency values (Hz) of the pure tone for each presentation ( f i r s t column) are depicted for sequence A (second column) and sequence B (third column). 55 161 Hx 50" . .^ y >-t 600 Hz £5 M ' i i i i 'i I i i i i i i i i i I i i i i i i i i i i i i i i i i i I i i i i i i i i i i i i i i 0 2 4 6 8 10 1£ IT 16 16 £0 ££ £4 £5 £8 30 3£ 34 36 38 40 H£ TT 46 48 50 PRESENTATION PATIENTi G . F . FUNDAMENTALi£00 Hz Fund 200 Hz SEOA SEOB 1 ) 300 133 2> 300 199 3) 200 199 4) 300 132 5) 300 132 6) 450 198 7) 450 132 8) 300 132 9) 300 198 10) 200 158 1 1 ) 250 158 12) 250 198 13) 200 158 14) 250 158 15) 312 198 16) 312 158 17) 250 158 18) 281 198 19) 316 176 20) 316 176 21 ) 281 198 22) 316 198 23) 316 176 24) 0 176 25) 0 198 26) 0 176 27) 0 176 Figure 12: Pitch matching control with noise for patient G.F. using a two-alternative forced choice adaptive method. Both the complex and pure tones were presented to the intact ear. The straight l i n e s represent the harmonic components of the complex test sound ( f l ) , i . e . , harmonics 3 - 1 0 . The graphic plots represent the frequency of the pure tone (f2) in r e l a t i o n to the component frequencies on a logarithmic scale. The upper plot is sequence A, the lower plot is sequence B. Plots were dependent on the patient's response after each presentation. On the r i g h t , actual frequency values (Hz) of the pure tone for each presentation ( f i r s t column) are depicted for sequence A (second column) and sequence B (third column). 57 16-e 1.00 0 . £ 5 £000 H E / I I I I I I I I I I I I I I I I I I I I I I I I •» I I 1 I I I I I I I I I I I I 1 I I I I I I I I I 0 e t 6 e 10 ie IT 16 ie es ee et £6 ee 30 ae at 36 38 40 te 7 7 46 te 5 0 P R E S E N T A T I O N , P A T I E N T 1 G . F . F U N D A M E N T A L 1 £ 0 0 H z Fund 200 Hz SEQA SEOB 1) 300 133 2) 300 199 3) 200 199 4) 300 298 5) 300 298 6) 200 198 7) 300 198 8) 300- 297 9) 375 198 10) 375 198 11) 300 297 12) 300 237 13) 375 237 14) 375 296 15) 300 236 16) 375 236 17) 375 295 18) 300 295 19) 337 235 20) 337 235 21) 300 294 22) 337 261 23) 337 261 24) 300 232 25) 337 232 26) 337 261 27) 0 261 28) 0 294 29) 0 261 30) 0 261 F i g u r e 13: P i t c h m a t c h i n g b e t w e e n e a r s f o r p a t i e n t G.F. u s i n g a t w o - a l t e r n a t i v e f o r c e d c h o i c e a d a p t i v e m e t h o d . The c o m p l e x t o n e was p r e s e n t e d t o t h e damaged e a r , and t h e p u r e t o n e t o t h e i n t a c t e a r . The s t r a i g h t l i n e s r e p r e s e n t t h e h a r m o n i c c o m p o n e n t s o f t h e c o m p l e x t e s t s o u n d (£1), i . e . , h a r m o n i c s 3 - 10. The g r a p h i c p l o t s r e p r e s e n t t h e f r e q u e n c y o f t h e p u r e t o n e ( f 2 ) i n r e l a t i o n t o t h e component f r e q u e n c i e s on a l o g a r i t h m i c s c a l e . The u p p e r p l o t i s s e q u e n c e A, t h e l o w e r p l o t i s s e q u e n c e B. P l o t s were d e p e n d e n t on t h e p a t i e n t ' s r e s p o n s e a f t e r e a c h p r e s e n t a t i o n . On t h e r i g h t , a c t u a l f r e q u e n c y v a l u e s (Hz) o f t h e p u r e t o n e f o r e a c h p r e s e n t a t i o n ( f i r s t c o l u m n ) a r e d e p i c t e d f o r s e q u e n c e A ( s e c o n d c o l u m n ) and s e q u e n c e B ( t h i r d c o l u m n ) . 59 1 6 i Hs 0 . £ 5 1 i i i i i i i i i i i i i i i i i i i i i i r i • i i i i i i i i i i i i i i i i i i i i i i i i i i 0 £ 7 6 6 10 1£ 14 16 16 £ 0 £ £ £ 4 £ 6 £ 8 3 0 3 £ 3 V 3 6 3 6 4 0 T£ V t 4 6 4 8 5 0 P R E S E N T A T I O N P A T I E N T i G - F - F U N D A M E N T A L i £ 0 0 Hz Fund 200 Hz SEOA SEOD 1) 300 133 2) 450 199 3) 450 132 4) 300 132 5) 450 198 6) 450 198 7) 300 132 e> 375 132 9) 375 198 10) 300 158 1.1 ) 375 158 12) 375 198 13) 300 158 14) 375 158 15) 375 198 16) 300 158 17) 337 158 18) 379 198 19) 379 198 20) 337 176 21 ) 379 176 22) 379 198 23) 0 176 24) 0 176 25) 0 198 26) 0 176 27) 0 176 Figure 14: Pitch matching between ears with noise for patient G.F. using a two-alternative forced choice adaptive method. The complex tone was presented to the damaged ear, and the pure tone to the intact ear. The straight lines represent the harmonic components of the complex test sound ( f l ) , i . e . , harmonics 3 - 10. The graphic plots represent the frequency of the pure tone (f2) in r e l a t i o n to the component frequencies on a logarithmic scale. The upper plot is sequence A, the lower plot is sequence B. Plots were dependent on the patient's response after each presentation. On the rig h t , actual frequency values (Hz) of the pure tone for each presentation ( f i r s t column) are depicted for sequence A (second column) and sequence B (third column). 61 16" e e1 1.00 0.£5 s o w a Hx 600 Hz i i i i i i i i i i i i i i i i i n i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i 0 £ T 6 6 10 1£ 1 T 16 16 £0 ££ £ 7 £6 £6 30 3£ 34 36 36 7 0 7 £ 7 7 46 H8 50 PRESENTATION PATIENTi G . F . FUNDAMENTALi£00 Hz F u n d 1) 2) 3) 4) 5) 6) 7) 8) 9) 10) 11) 12) 13) 14) 15) 16) 17) 18) 19) 20) 21 > 22) 23) 24) 25) 26) 27) 28) 29) 200 SEQA 300 300 200 300 300 200 300 300 200 250 250 312 312 250 312 312 250 281 281 250 281' 281 316 316 0 0 0 0 0 Hz SEOB 133 199 199 298 198 198 297 297 198 198 297 237 237 296 236 236 295 235 235 294 294 261 261 294 261 261 294 261 261 F i g u r e 15: Pitch matching control for patient L.F. using a two-alternative forced choice adaptive method. Both the complex and 1pure tones were presented to the intact ear. The straight l i n e s represent the harmonic components of the complex test sound ( f l ) , i . e . , harmonics 3 - 7 . The graphic plots represent the frequency of the pure tone (f2) in r e l a t i o n to the component frequencies on a logarithmic scale. The upper plot is sequence A, the lower plot is sequence B. Plots were dependent on the patient's response after each presentation. On the r i g h t , actual frequency values (Hz) of the pure tone for each presentation ( f i r s t column) are depicted for sequence A (second column) and sequence B (third column). 63 i&1 aiacf Hi 6" 4-4. M M 900 Hz 1.001 0, £5 I i i i i i i i "i i i i i i i i i i l i l I I i i I l l I I I i i 'i T i i i i i I I I i i I i i I i i 0 £ T 6 6 10 1£ 14 16 18 £0 ££ £ 7 £6 £9 90 3£ 37 36 59 70 4£ 7 7 46 78 50 PRESENTATION PATIENT 1 L . F . FUNDAMENTAL 1300 Hz Fund 300 Hz 8EQA SEOB 1 ) 450 200 2) 450 300 3> 300 200 4) 450 200 5) 450 300 6) 300 200 7) 450 200 8) 450 300 9) 300 239 10) 375 239 11) 375 299 12) 300 239 13) 375 239 14) 375 299 15) 300 239 16) 375 239 17) 375 299 18) 300 265 19) 337 265 20) 337 298 21) 300 264 22) 337 264 23) 337 297 24) 300 264 25) 337 264 26) 337 0 Figure 16: Pitch matching control with noise for patient L.F. using a two-alternative forced choice adaptive method. Both the complex and pure tones were presented to the intact ear. The straight lines represent the harmonic components of the complex test sound ( f l ) , i . e . , harmonics 3 - 7 . The graphic plots represent the frequency of the pure tone (f2) in r e l a t i o n to the component frequencies on a logarithmic scale. The upper plot is sequence A, the lower plot is sequence B. Plots were dependent on the patient's response after each presentation. On the r i g h t , actual frequency values (Hz) of the pure tone for each presentation ( f i r s t column) are depicted for sequence A (second column) and sequence B (third column). 65 1&1 S 1 0 0 HE 6-S00. Hz e1 1.00 0.50 01 £5 I i i' i i i i i i i r i i i i i i i i i i i i i i i I i I i i i i i i i i i i r i v i i i i i i i i i 1 7 ) 0 2 7 6 8 10 1£ 14 16 16 £0 ££ £t £6 £8 3 PRESENTATION PATIENTi L . F . FUNDAMENTAL•300 Hz Fund 300 Hz SEQA SEOB 1) 450 200 2) 450 300 3) 300 200 4) 450 200 5) 450 300 6) 300 200 7) 450 200 8) 450 300 9) 300 239 10) 375 239 11) 375 299 12) 300 239 13) 375 239 14) 375 299 15) 300 239 16) 375 239 17) 375 299 18) 300 265 19) 337 265 20) 337 298 21 ) 379 264 22) 379 264 23) 337 297 24) 379 . 264 25) 379 264 Figure 17: Pitch matching between ears for patient L.F. using a two-alternative forced choice adaptive method. The complex tone was presented to the damaged ear, and the pure tone to the intact ear. The straight lines represent the harmonic components of the complex test sound (£1), i . e . , harmonics 3 - 7 . The graphic plots represent the frequency of the pure tone (f2) in r e l a t i o n to the component frequencies on a logarithmic scale. The upper plot is sequence A, the lower plot is sequence B. Plots were dependent on the patient's response after each presentation. On the r i g h t , actual frequency values (Hz) of the pure tone for each presentation ( f i r s t column) are depicted for sequence A (second column) and sequence B (third column). 67 16" £ 1 0 0 Hi £' 00" 501 800 H z £5 I I l I I i I i I i i I I I l i I I I i l I" M l I l I I i l i I i I i I i i i I i i i I i i i I i i 0 £ 4 6 6 10 1£ I T 16 16 £0 £ £ £ T £6 £8 30 3£ 3 T 36 38 70 T £ T T T 6 T 8 50 P R E S E N T A T I O N P A T I E N T i L . F . F U N D A M E N T A L i 3 0 0 H z Fund 300 Hz SEOA SEOB 1 > 450 200 2) 450 300 3) 300 200 4) 450 200 5) 450 300 6) 300 200 7) 450 200 8) 450 300 9) 300 239 10) 375 239 11) 375 299 12) 300 239 13) 375 239 14) 375 299 15) 300 239 16) 375 239 17) 375 • 299 18) 300 265 19) 337 265 20) 337 298 21) 300 264 22) 337 264 23) 337 297 24) 300 264 25) 337 264 26) 337 0 Figure 18: Pitch matching between ears with noise for patient L.F. using a two-alternative forced choice adaptive method. The complex tone was presented to the damaged ear, and the pure tone to the intact ear. The straight lines represent the harmonic components of the complex test sound ( f l ) , i . e . , harmonics 3 - 7. The graphic plots represent the frequency of the pure tone (£2) in r e l a t i o n to the component frequencies on a logarithmic scale. The upper plot is sequence A, the lower plot is sequence B. Plots were dependent on the patient's response after each presentation. On the right, actual frequency values (Hz) of the pure tone for each presentation ( f i r s t column) are depicted for sequence A (second column) and sequence B (third column). 69 16" e e 1 . 0 0 £ 1 0 0 Hx 300 Hz 01 £5 i i i i i i i i ' M i i i i i i i i i" i i i i i "i i i i i i i i i i i i i i i i i i i i i i i i i 0 £ t 6 8 10 1£ It 16 18 £0 ££ £t £6 £8 30 3£ 3t 36 36 t0 t£ t t t6 t8 PRESENTATION PATIENTi L.F. FUNDAMENTALi300 Hz n r 50 Fund 300 Hz SEOA SEOB 1) 450 200 2) 450 300 3) 300 200 4) 450 200 5) 450 300 6) 300 200 7) 450 200 8) 450 300 9) 300 239 10) 375 239 1 1) 375 299 12) 300 239 13) 375 239 14) 375 299 15) 300 239 16) 375 239 17) 375 299 18) 300 265 19) 337 265 20) 337 235 21 ) 300 235 22) 337 264 23) 337 234 24) 300 234 25) 337 0 26) 337 0 Figure 19: Pitch matching control for patient R.L. using a two-alternative forced choice adaptive method. Both the complex and pure tones were presented to the intact ear. The straight lines represent the harmonic components of the complex test sound ( f l ) , i . e . , harmonics 3 - 7 . The graphic plots represent the frequency of the pure tone (f2) in r e l a t i o n to the component frequencies on a logarithmic scale. The upper plot is sequence A, the lower plot is sequence B. Plots were dependent on the patient's response after each presentation. On the right, actual frequency values (Hz) of the pure tone for each presentation ( f i r s t column) are depicted for sequence A (second column) and sequence B (third column) . 71 h A R M 0 N I 16 61 4 £ 1 1.00 0.£5 8100 Hx 900 Hz i I I I i I I I I I I I I I I I I I I I I I 1 I I I'l I I I I I i I I I I I I I I I l l I I I I I l 0 2 4 6 8 10 1£ 14 16 18 £0 ££ £4 £6 £6 30 3£ 34 36 38 40 4£ 44 46 48 50 PRESENTATION PATIENTi K - L - FUNDAMENTAL1300 Hz Fund 300 Hz SEOA SEOB 1 > 450 200 2) 675 300 3) 675 300 4) 450 450 5) 675 300 6) 675 300 7) 450 450 8) 562 300 9) 562 300 10) 702 450 11 ) 702 359 12) 562 287 13) 702 287 14) 702 359 15) 562 287 16) 632 287 17) 711 359 18) 711 319 19) 632 319 20) 711 283 21 > 711 283 22) 0 318 23) 0 282 24) 0 282 F i g u r e 20: P i t c h m a t c h i n g c o n t r o l w i t h n o i s e f o r p a t i e n t R . L . u s i n g a t w o - a l t e r n a t i v e f o r c e d c h o i c e a d a p t i v e m e t h o d . B o t h t h e c o m p l e x a n d p u r e t o n e s w e r e p r e s e n t e d t o t h e i n t a c t e a r . T he s t r a i g h t l i n e s r e p r e s e n t t h e h a r m o n i c c o m p o n e n t s o f t h e c o m p l e x t e s t s o u n d ( f l ) , i . e . , h a r m o n i c s 3 - 7 . T h e g r a p h i c p l o t s r e p r e s e n t t h e f r e q u e n c y o f t h e p u r e t o n e (f2) i n r e l a t i o n t o t h e c o m p o n e n t f r e q u e n c i e s on a l o g a r i t h m i c s c a l e . T he u p p e r p l o t i s s e q u e n c e A , t h e l o w e r p l o t i s s e q u e n c e B . P l o t s w e r e d e p e n d e n t on t h e p a t i e n t ' s r e s p o n s e a f t e r e a c h p r e s e n t a t i o n . On t h e r i g h t , a c t u a l f r e q u e n c y v a l u e s ( H z ) o f t h e p u r e t o n e f o r e a c h p r e s e n t a t i o n ( f i r s t c o l u m n ) a r e d e p i c t e d f o r s e q u e n c e A ( s e c o n d c o l u m n ) a n d s e q u e n c e B ( t h i r d c o l u m n ) . 7 3 1 6 - slaw H J 1.00" 01 £ 5 1 i i l i i i ' i i i i i i i i i i i i i i i i i i i I l l I i I l i i l i i I l i l l i i i I I I I i 0 £ 7 6 6 10 te I T 16 18 £ 0 £ £ £ 4 £ 6 £ 6 3i P R E S E N T A T I O N P A T I E N T i R.L. F U N D A M E N T A L i 3 0 0 Hz Fund 300 Hz SEOA SEOB 1) 450 200 2) 450 200 3) 300 300 4) 450 300 5) 450 450 6) 300 300 7) 450 300 8) 450 450 9) 300 300 10) 375 300 11) 375 450 12) 300 359 13) 375 359 14) 468 449 15) 468 359 16) 374 359 17) 420 449 18) 420 359 19) 472 359 20) 472 449 21 ) 420 399 22) 472 399 23) 472 449 24) 0 399 25) 0 399 26) 0 449 27) 0 399 28) 0 399 F i g u r e 2 1 : Pitch matching between ears for patient R.L. using a two-alternative forced choice adaptive method. The complex tone was presented to the damaged ear, and the pure tone to the Intact ear. The straight l i n e s represent the harmonic components of the complex test sound ( f l ) , i . e . , harmonics 3 - 7 . The graphic plots represent the frequency of the pure tone ( f 2 ) in r e l a t i o n to the component frequencies on a logarithmic scale. The upper plot is sequence A, the lower plot is sequence B. Plots were dependent on the patient's response after each presentation. On the r i g h t , actual frequency values (Hz) of the pure tone for each presentation ( f i r s t column) are depicted for sequence A (second column) and sequence B (third column). 7 5 16- £ 1 0 0 Hz • 6- : 1 . 0 0 1 9 0 0 Hz 0.£5 I i i i i i i i i i i i i i i i i i i i i i i i i i i i l i i i i i i i i i i r i r i i i r i i i i i 0 £ t 6 6 10 1£ I t 16 19 £0 £E £t £6 £9 3 0 3£ 3 t 36 3 9 t 0 t£ t t t 6 t 9 5 0 P R E S E N T A T I O N P A T I E N T i R.L. F U N D A M E N T A L i 3 0 0 Hz Fund 300 Hz SEOA SEQP 1) 450 200 2) 450 300 3) 300 300 4) 300 450 5) 450 300 6) 450 300 7) 300 450 8) 450 300 9) 450 300 10) 300 450 1 1 ) 375 359 12) 468 359 13) 468 449 14) 374 359 15) 467 359 16) 467 449 17) 374 359 18) 420 359 19) 472 449 20) 472 399 21) 420 399 22) 472 449 23) 472 399 24) 0 399 25) 0 449 26) 0 399 27) 0 399 Figure 22: Pitch matching between ears with noise for patient R.L. using a two-alternative forced choice adaptive method. The complex tone was presented to the damaged ear, and the pure tone to the intact ear. The straight lines represent the harmonic components of the complex test sound ( f l ) , i . e . , harmonics 3 - 7 . The graphic plots represent the frequency of the pure tone (f2) in r e l a t i o n to the component frequencies on a logarithmic scale. The upper plot is sequence A, the lower plot is sequence B. Plots were dependent on the patient's response after each presentation. On the r i g h t , actual frequency values (Hz) of the pure tone for each presentation ( f i r s t column) are depicted for sequence A (second column) and sequence B (third column). 77 161 B100 Ha 6' 9 0 0 Hz £ 1 i . 0 0 -0 . £ 5 I i i i i i i i i i i i i i i i i i r i i i i i i i i i i i i i i i i i i i i i i i i i i i i'» i i i 0 £ 4 6 6 1 0 1 £ I T 1 6 1 6 £ 0 £ £ £ 4 £ 6 £ 8 3 J PRESENTATION PATIENTi R.L. FUNDAMENTALi300 Hz Fund 300 Hz SEQA SEOB 1 > 450 200 2) 450 300 3) 300 300 4) 450 450 5) 450 300 6) 300 300 7) 450 450 8) 450 300 9) 300 300 10) 375 450 11) 468 359 12) 468 359 13) 374 449 14) 467 359 15) 467 359 16) 374 449 17) 420 359 18) 420 359 19) 420 449 20) 373 399 21 ) 419 354 22) 419 314 23) 372 314 24) 418 0 25) 418 0 F i g u r e 23: P i t c h matching c o n t r o l f o r p a t i e n t J.w. using a t w o - a l t e r n a t i v e f o r c e d c h oice adaptive method. Both the complex and pure tones were presented to the i n t a c t ear. The s t r a i g h t l i n e s r e p r e s e n t the harmonic components of the complex t e s t sound ( f l ) , i . e . , harmonics 3 - 1 0 . The graphic p l o t s r e p r e s e n t the frequency of the pure tone (f2) i n r e l a t i o n to the component f r e q u e n c i e s on a l o g a r i t h m i c s c a l e . The upper p l o t i s sequence A, the lower p l o t i s sequence B. P l o t s were dependent on the p a t i e n t ' s response a f t e r each p r e s e n t a t i o n . On the r i g h t , a c t u a l frequency values (Hz) of the pure tone f o r each p r e s e n t a t i o n ( f i r s t column) are d e p i c t e d f o r sequence A (second column) and sequence B ( t h i r d column). 79 16-8" 4 £ ' i . m 7000 Hx N /A/A/-^A^v^s^* t\m Hz 0 1 £ 5 I i i i i i i i i i i i i i i i i i i i i i I I " i i i I I i I i l i M i i i i i i i i i i i i i i i 0 £ 4 6 8 10 I S 14 15 18 £0 ££ £4 £6 £8 30.38 34 3 6 3 8 4 0 4£ 4 4 4 6 4 6 P R E S E N T A T I O N P A T I E N T i j . w . FUNDAMENTAL•700 Hz 5 0 Fund: 700 Hz SEOA SEOB 1) 1050 467 2) 1575 700 3) 1575 466 4) 1050 466 5) 1575 310 6) 1575 310 7) 1050 465 8) 1312 371 9) 1640 296 10) 1640 296 1 1) 1312 370 12) 1640 370 13) 1640 463 14) 1312 370 15) 1476 370 16) 1476 328 17) 1312 291 18) 1476 291 19) 1476 327 20) 1312 327 21 ) 1476 290 22) 1476 290 Figure 24: Pitch matching control with noise for patient J.W. using a two-alternative forced choice adaptive method. Both the complex and pure tones were presented to the intact ear. The straight lines represent the harmonic components of the complex test sound ( f l ) , i . e . , harmonics 3 - 10. The graphic plots represent the frequency of the pure tone (f2) in r e l a t i o n to the component frequencies on a logarithmic scale. The upper plot is sequence A, the lower plot is sequence B. Plots were dependent on the patient's response after each presentation. On the r i g h t , actual frequency values (Hz) of the pure tone for each presentation ( f i r s t column) are depicted for sequence A (second column) and sequence B (third column). 81 7000 H r X £100 Hz i i i i i i 11 0 8 4 6 6 i i i i t i i i i i i i i i i i i i i i i i i i ' i i t i 'i i i i i i i i i i i i i i " 10 1£ 14 16 18 £0 ££ £4 £6 £8 30 3£ 34 36 38 40 4£ 44 46 48 50 PRESENTATION PATIENT" J . W . FUNDAMENTALi700 Hz Fund 700 Hz SEOA SEOB 1) 1050 467 2) 1050 700 3> 1050 700 4) 700 1050 5) 1050 700 6) 1050 700 7) 700 1050 8) 1050 700 9) 1050 700 10) 700 1050 11) 875 839 12) 1093 671 13) 1093 671 14) 874 839 15) 1092 671 16) 1092 671 17) 874 839 18) 983 745 19) 983 745 20) 874 838 21 ) 983 744 22) 1 105 744 23) 1 105 837 Figure 25: Pitch matching between ears for patient J.W. using a two-alternative forced choice adaptive method. The complex tone was presented to the damaged ear, and. the pure tone to the intact ear. The straight lines represent the harmonic components of the complex test sound ( f l ) , i . e . , harmonics 3 - 10. The graphic plots represent the frequency of the pure tone (f2) in r e l a t i o n to the component frequencies on a logarithmic scale. The upper plot is sequence A, the lower plot is sequence B. Plots were dependent on the patient's response after each presentation. On the rig h t , actual frequency values (Hz) of the pure tone for each presentation ( f i r s t column) are depicted for sequence A (second column) and sequence B (third column). 83 16" 6' T " E" 1.00" fli.Efli" 0.S5-7000 Ha \ £ 1 0 0 Hz i i i i i i i i i i i i i i i i i i ' i i i i n i i " i i i i i i i i i i i i i i i i i i i i i i i i 0 £ T 6 6 10 I E I t 16 16 £0 £E £t £6 £6 30 3 E 3 t 36 3 6 t 0 t£ t t t 6 t 6 5 0 P R E S E N T A T I O N P A T I E N T i J . w . F U N D A M E N T A L i 7 0 0 Hz Fund 700 Hi S E O A S E Q B 1) 1050 467 2) 1050 700 3) 1575 700 4) 1575 1050 5) 1050 700 6) 1575 700 7) 1575 1050 8) 1050 700 9 ) 1312 700 10) 1312 1050 11) 1050 839 12) 1312 839 13) 1312 671 14) 1050 671 15) 1312 839 16) 1312 83*9 17) 1050 1049 18) 1181 839 19) 1328 839 20) 1328 1049 21 ) 1 180 932 22) 1 180 828 23) 1049 828 24) 1049 931 25) 1 180 827 26) 1 180 0 F i g u r e 26: Pitch matching between ears with noise for patient J.W. using a two-alternative forced choice adaptive method. The complex tone was presented to the damaged ear, and the pure tone to the intact ear. The straight lines represent the harmonic components of the complex test sound ( f l ) , i . e . , harmonics 3 - 10. The graphic plots represent the frequency of the pure tone (f2) in r e l a t i o n to the component frequencies on a logarithmic scale. The upper plot is sequence A, the lower plot is sequence B. Plots were dependent on the patient's response after each presentation. On the rig h t , actual frequency values (Hz) of the pure tone for each presentation ( f i r s t column) are depicted for sequence A (second column) and sequence B (third column). 85 16 e t e 1. 7000 H s \ _ £100 Hz 0,£5 I I I l l I l i l i l l I l l i l I I i I l l i I i I l ' I I I l l i I I I I I l I I l I I I I i l l I 0 £ t 6 6 10 1£ I T 16 18 £0 £ £ £ T £6 £8 30 3£ 3 T 36 38 t0 T £ T T t6 T8 50 PRESENTrtTION PrlTIENTi j.w. FUNDAMENTAL!700 Hz Fund 700 Hz SEOA SEOB 1 > 1050 467 a) 1050 700 3) 1050 700 4) 1050 466 5) 700 466 6) 1050 699 7) 1050 466 8) 700 466 9) 1050 699 10) 1050 699 1 1 ) 700 559 12) 875 559 13) 875 699 14) 700 699 15) 875 874 16) 1093 699 17) 1093 699 18) 874 559 19) 983 559 20) 983 699 21 ) 1105 699 22) 1 105 874 23) 982 776 24) 982 689 25) 1 104 689 26) 1 104 775 27) 0 688 28) 0 688 Table 4,: Pitch values assigned to the pitch of the complex test sound by patient A.D. for sequences A and B for each procedural method using the two-alternative forced choice adaptive routine. Below each sequence is the frequency value representing either the fundamental of the complex, i t s harmonic components, or octaves below harmonics, which best approximate the pitch values. Dashed lin e represents no match. 87 P a t i e n t ; ; A.D. Fr eq. approx (Hz) Pitch Matching Procedure P.M. control P.M. control P.M. betw. P.M. betv. with noise ears ears w. noise Seq. A pitch value (Hz) 478 +/- 32 239 +/- 23 508+/-49 713 +/- 68 Freq. approx, (Hz) 450 (oct. bel. 3rd har.) 750 (oct. b el. 5th har.) Seq. B pitch value (Hz) 90 + /- 9 132 +/- 9 215+/-21 260 +/- 30 range of frequency values to which an exact matching to the fundamental occurs: 281 - 319 Hz 88 Table 5: Pitch values assigned to the pitch of the complex test sound by patient A.F. for sequences A and B for each procedural method using the two-alternative forced choice adaptive routine. Below each sequence is the frequency value representing either the fundamental of the complex, i t s harmonic components, or octaves below harmonics, which best approximate the pitch values . Dashed lin e represents no match. 89 Patient: A.F. Pitch Matching Procedure P.M. control P.M. control P.M. betv. P.M. betw. with noise ears ears w. noise Seq. A pitch value (Hz) 299 +/- 20 266 +/- 18 2 6 6 + / - 1 8 266 +/- 18 Freq. approx. (Hz) 300 (oct. bel. 3rd har.) Seq. B pitch value (Hz) 278 +/- 19 278 +/- 19 278+/-19 247 +/- 17 Freq. approx (Hz) 300 (oct. bel. 3rd har.) 300 (oct. bel. 3rd har.) 300 (oct. bel 3rd har) range of frequency values to which an exact matching to the fundamental occurs: 183 - 212 Hz 90 Table 6 : Pitch values assigned to the pitch of the complex test sound by patient G.F. for sequences A and B for each procedural method using the two-alternative forced choice adaptive routine. Below each sequence is the frequency value representing either the fundamental of the complex, i t s harmonic components, or octaves below harmonics, which best approximate the pitch values. Dashed l i n e represents no match. 91 Patient: G.F. Pitch Matching Procedure P.M. control P.M. control P.M. betw. P.M. betw with noise ears ears w. noise Seq. A pitch value (Hz) 299 +/- 20 319 +/- 21 358+/-24 282 +/- 27 Freq. approx (Hz) 300 (oct. b el. 3rd har.) 300 (oct. b el. 3rd har . ) 400 (2nd har . ) 300 (oct. b el. 3rd har.) Seq. B pitch value (Hz) 187 +/- 13 262 +/- 25 187+/-13 278 +/- 19 Freq. approx (Hz) 200 (fund.) 200 (fund . ) 300 (oct. b el. 3rd har.) range of frequency values to which an exact matching to the fundamental occurs: 183 - 212 Hz 92 Table 7: Pitch values assigned to the pitch of the complex test sound by patient L.F. for sequences A and B for each procedural method using the two-alternative forced choice adaptive routine. Below each sequence is the frequency value representing either the fundamental of the complex, i t s harmonic components, or octaves below harmonics, which best approximate the pitch values. Dashed l i n e represents no match. 93 paUent ; L . F . Pitch Matching Procedure P.M. control P.M. control P.M. betw. P.M. betw, with noise ears ears w. noise Seq. A pitch value (Hz) 319 +/- 21 358 +/- 24 319+/-21 319 +/- 21 Freq. approx. (Hz) 300 (fund. ) 300 (fund.) 300 (fund.) Seq. B pitch value (Hz) 281 +/- 19 281 +/- 19 281+/-19 250 +/- 17 Freq. approx (Hz) 300 (fund.) 300 (fund.) 300 (fund.) range of frequency values to which an exact matching to the fundamental occurs: 281 - 319 Hz 94 Table 8 : Pitch values assigned.to the pitch of the complex test sound by patient R.L. for sequences A and B for each procedural method using the two-alternative forced choice adaptive routine. Below each sequence is the frequency value representing either the fundamental of the complex, i t s harmonic components, or octaves below harmonics, which best approximate the pitch values. Dashed l i n e represents no match. 95 P a t i e n t ; R.L. Pitch Matching Procedure P.M. control P.M. control P.M. betw. P.M. betw. with noise ears ears w. noise Seq. A pitch value (Hz) 672 + /- 46 446 +/- 30 446+/-30 396 +/- 27 Freq. approx (Hz) 600 (2nd har . ) 450 (oct. b el. 3rd har . ) 450 (oct. bel 3rd har) Seq. B pitch value (Hz) 301 +/- 21 424 +/- 29 424+/-29 379 +/- 58 Freq. approx (Hz) 300 (fund. ) 450 (oct. be 1. 3rd har.) 450 (oct. bel 3rd har) range of frequency values to which an exact matching to the fundamental occurs: 281 - 319 Hz 96 Table 9; Pitch values assigned to the pitch of the complex test sound by patient J . W . for sequences A and B for each procedural method using the two-alternative forced choice adaptive routine. Below each sequence is the frequency value representing either the fundamental of the complex, i t s harmonic components, or octaves below harmonics, which best approximate the pitch values. Dashed lin e represents no match. 97 Patient: J.W. Pitch Matching Procedure P.M. control P.M. control P.M. betw. P.M. betw with noise ears ears w. noise Seq. A pitch value (Hz) 1394 +/- 95 986 +/- 94 1184 +/-114 1044 +/- 70 Freq. approx, (Hz) Seq. B pitch value (Hz) 1400 (2nd har.) 309 +/- 21 1050 (oct. bel. 3rd har.) 791 +/- 54 880+/-60 1050 (oct. bel. 3rd har.) 732 +/- 50 Freq. approx (Hz) 700 (fund.) range of frequency values to which an exact matching to the fundamental occurs: 657 - 742 Hz 98 o£ an exact match is 281-319 Hs. i) Pitch matching control Figures 11, 15, and 19 and tables 6, 7, and 8 show that patients G.F., L.F., and R.L. matched the complex test sound to i t s fundamental frequency when both the complex test sound and the comparison pure tone were presented to the intact ear (pitch matching c o n t r o l ) . Both G.F. and R.L. matched to the fundamental when sequence B was used ( i . e . , the pure tone's s t a r t i n g frequency presented lower than the fundamental of the complex), while patient L.F. matched to the fundamental regardless of which sequence was Implemented. Patients A.D. (figure 3; table 4), A.F. (figure 7; table 5), and G.F. (figure 11; table 6) matched to the octave below the t h i r d harmonic, while R.L. and J.W. (figures 19 and 23; tables 8 and 9) matched to the (not presented) second harmonic (the octave above the fundamental) during the pitch matching control procedure. A.F. displayed octave confusion during pitch matching regardless of the sequence. U J Pitch matching control with noise With the addition of the low-pass f i l t e r e d noise to the complex test sound while s t i l l maintaining both complex and 99 pure tones to the i n t a c t ear, p a t i e n t s A.D. ( f i g u r e 4; t a b l e 4) and A.F. ( f i g u r e 8; t a b l e 5) f a i l e d again to match the complex to the fundamental as they d i d without the n o i s e . P a t i e n t s R.L. and J.W. ( f i g u r e s 20 and 24; t a b l e s 8 and 9), who matched e i t h e r to the fundamental or to the octave above the fundamental d u r i n g p i t c h matching c o n t r o l , f a i l e d to do so i n the presence of noise and i n s t e a d matched e i t h e r to the octave below the t h i r d harmonic or had no match at a l l . Furthermore, p a t i e n t G.F. ( f i g u r e 12; t a b l e 6), who matched e i t h e r to the fundamental or to the octave below the t h i r d harmonic d u r i n g p i t c h matching c o n t r o l , f a i l e d to match to the fundamental i n the presence of n o i s e . P a t i e n t L.F., however, s t i l l matched to the fundamental even i n the presence of n o i s e , but now o n l y i n sequence B ( f i g u r e 16; t a b l e 7). I l l ) Pitch matching between e a r s When the complex t e s t sound was presented to the damaged ear and the comparison pure tone to the i n t a c t ear ( i . e . , p i t c h matching between ears) both G.F. and L.F. matched the complex with i t s fundamental, as they d i d when both sounds were presented to t h e i r i n t a c t ears ( f i g u r e 13 and 17; t a b l e s 6 and 7). In a d d i t i o n , p a t i e n t G.F., who had matched to the octave below the t h i r d harmonic d u r i n g p i t c h matching c o n t r o l f o r sequence A, now matched to the octave 100 above the fundamental d u r i n g p i t c h matching between ears for the same sequence. P a t i e n t s R.L. and J.W., however, f a i l e d to match to the fundamental or to the second harmonic as they d i d when both sounds were presented to t h e i r i n t a c t ear, and i n s t e a d matched to the octave below the t h i r d harmonic ( f i g u r e 21; t a b l e 8) or had no match a t a l l ( f i g u r e 25; t a b l e 9 ) . P a t i e n t s A.D. and A.F. ( f i g u r e s 5,9; t a b l e s 4,5) continued to have d i f f i c u l t y matching to the fundamental s i n c e no match to any component occurred except i n one case when there was a match to the octave below the t h i r d harmonic. IvJ P i t c h matching between ears with noise A d d i t i o n of low-pass f i l t e r e d noise to the complex t e s t sound dur i n g p i t c h matching between ears r e s u l t e d i n p r e s e r v a t i o n of the a b i l i t y of p a t i e n t L.F. to p i t c h match to the l a c k i n g fundamental ( f i g u r e 18; t a b l e 7), but only d u r i n g sequence A. One p a t i e n t (J.W.) who had not p r e v i o u s l y matched to the fundamental d i d so d u r i n g t h i s procedure i n sequence B ( f i g u r e 26; t a b l e 9). Octave c o n f u s i o n to the octave below the t h i r d harmonic was a l s o d i s p l a y e d , however, f o r t h i s p a t i e n t . P a t i e n t G.F. was unable to match to the fundamental with the a d d i t i o n of noise to the complex i n s p i t e of h i s 101 apparent a b i l i t y to do so without noise. Instead he matched to the octave below the t h i r d harmonic during both sequences (figure 14; table 6). No reasonable match was made during t h i s procedure for patients A.D., A.F., and R.L. (figures 6,10,22: tables 4,5,8) except once when a match was made by patient A.D. to the octave below the f i f t h harmonic. Pitch Matching of Complex Tones Using an Up-Down Adjustment Technique Results of the pitch matching between the complex and pure tones using the up-down adjustment technique are shown in tables 10 to 14. JJ Pitch matching control Tables 10 to 14 show that a l l the patients except A.F. matched the complex test sound to i t s fundamental frequency at least once when both the complex test sound and the comparison pure tone were presented to the intact ear (pitch matching c o n t r o l ) . For patients L.F. and R.L. .(tables 13 and 14, respectively) this occurred regardless of whether the s t a r t i n g frequency of the pure tone (f2) was above or below the fundamental frequency of the complex ( f l ) . However, the matching to the fundamental occurred twice for A.D., only when the st a r t i n g frequency of f2 was above the fundamental frequency, and once for G.F., only when the 102 Table 10: Pitch values assigned to the pitch of. the complex test sound by patient A.D. for each procedural method using the up-down adjustment technique. Listed are the values obtained when the patient started the match with the pure tone frequency above or below that of the fundamental of the complex. In parentheses is the frequency value representing either the fundamental of the complex, i t s harmonic components, or octaves below harmonics, which best approximate the pitch values. A dashed l i n e represents no match. 103 Patient; A.D. Pitch Matchina Procedure P.M. control P.M. control P .M. betw. P.M. betw. with noise ears ears w. noi Pitch 274 332 329 291 value ( 300 - (300 - (300 - (300 -with fund.) fund.) fund.) fund.) s t a r t . f req. 297 894 549 312 above ( 300 - (900 - (600 - ( 300 -fund. fund.) 3rd har.) 2nd har. ) fund.) (Hz) Pitch 583 159 474 167 value ( 600 - (150 - (450 - (150 -with 2nd har. ) oct. bel. oct. bel. oct. bel. s t a r t . fund.) 3rd har. ) fund.) freq. below 589 810 679 501 fund. (600 - (900 - (750 - ( 450 -(Hz) 2nd har . ) 3rd har.) oct. bel. oct. bel. 5th har.) 3rd har . ) 104 T a b l e 1 1 : P i t c h v a l u e s a s s i g n e d t o t h e p i t c h o f t h e c o m p l e x t e s t s o u n d b y p a t i e n t A . F . f o r e a c h p r o c e d u r a l m e t h o d u s i n g t h e u p - d o w n a d j u s t m e n t t e c h n i q u e . L i s t e d a r e t h e v a l u e s o b t a i n e d when t h e p a t i e n t s t a r t e d t h e m a t c h w i t h t h e p u r e t o n e f r e q u e n c y a b o v e o r b e l o w t h a t o f t h e f u n d a m e n t a l o f t h e c o m p l e x . I n p a r e n t h e s e s i s t h e f r e q u e n c y v a l u e r e p r e s e n t i n g e i t h e r t h e f u n d a m e n t a l o f t h e c o m p l e x , i t s h a r m o n i c c o m p o n e n t s , o r o c t a v e s b e l o w h a r m o n i c , w h i c h b e s t a p p r o x i m a t e t h e p i t c h v a l u e s . A d a s h e d l i n e r e p r e s e n t s no m a t c h . 105 Pitch Matching Procedure M. control P.M. control P.M. betw. P.M. betw. with noise ears ears w. noise 588 437 408 200 (600 - (400 - (400 - (200 -3rd har.) 2nd har.) 2nd har.) fund.) 737 446 412 581 (- - -) (400 - (400 - (600 -2nd har.) 2nd har.) 3rd har.) 811 ( 800 -4th har . ) 411 318 140 223 (400 - (300 - (- - -) (200 -2nd har.) oct. bei. fund.) 3rd har.) 435 411 183 248 (400 - (400 - (200 - (- - -) 2nd har.) 2nd har.) fund.) 470 (500 -oct. bei. 5th har.) 602 ( 600 -3rd har.) 106 Table 12: Pitch values assigned to the pitch of the complex test sound by patient G.F. for each procedural method using the up-down adjustment technique. Listed are the values obtained when the patient started the match with the pure tone frequency above or below that of the fundamental of the complex. In parentheses is the frequency value representing either the fundamental of the complex, i t s harmonic components, or octaves below harmonics, which best approximate the pitch values. A dashed lin e represents no match. 107 Pitch Matching Procedure M. control P.M. control P.M. betw. P.M. betw. with noise ears ears w. noise 496 (500 -oct. bel. 5th har.) 589 ( 600 -3rd har.) 795 ( 800 -4th har.) 813 (800 -4th har.) 830 ( 800 -4th har.) 881 (800 -4th har.) 132 ( ) 134 ( ) 1110 (1000 -5th har. ) 135 ( ) 204 ( 200 -fund.) 641 (600 -3rd har. ) 192 797 191 137 (200 - (800 - (200 - (- - -) fund.) 4th har.) fund.) 639 814 574 685 (600 - (800 - (600 - (- - -) 3rd har.) 4th har.) 3rd har.) 812 878 901 908 (800 - (800 - (--•-) (- - -) 4th har.) 4th har.) 108 Table 13: Pitch values assigned to the pitch of the complex test sound by patient L.F. for each procedural method using the up-down adjustment technique. Listed are the values obtained when the patient started the match with the pure tone frequency above or below that of the fundamental of the complex. In parentheses is the frequency value representing either the fundamental of the complex, i t s harmonic components, or octaves below harmonics, which best approximate the pitch values. A dashed l i n e represents no match. 109 P a t i e n t : L . F . Pitch Matching P r o c e c i u K e P i t c h va lue wi th s t a r t . f r e q . above f u n d . (Hz) P . M . c o n t r o l 296 ( 300 -f u n d . ) 301 ( 300 -f u n d . ) 691 (750 -o c t . b e i . 5th h a r . ) 897 (900 -3rd h a r . ) P . M . c o n t r o l wi th no i se 302 ( 300 -f u n d . ) 306 ( 300 -f u n d . ) P . M . betw, ears 286 (300 -f u n d . ) 287 ( 300 -f u n d . ) 290 ( 300 -f u n d . ) 291 ( 300 -f u n d . ) 366 373 397 ) P . M . betw. ears w. no i se 204 ( ) 210 ) 354 364 ( ) 375 3 89 389 ( ) P i t c h va lue wi th s t a r t . f r e q . be low f u n d . (Hz) 188 ( ) 291 (300 -f u n d . ) 297 ( 300 -f u n d . ) 298 (300 -f u n d . ) 301 (300 -f u n d . ) 286 ( 300 -f u n d . ) 290 ( 300 -f u n d . ) 290 (300 -f u n d . ) 210 ( ) 212 ( ) 339 ( ) 239 349 376 376 394 ( ) 372 378 380 387 401 ( ) 110 Table 14? P i t c h v a l u e s a s s i g n e d t o t h e p i t c h o f t h e c o m p l e x t e s t s o u n d b y p a t i e n t R . L . f o r e a c h p r o c e d u r a l m e t h o d u s i n g t h e u p - d o w n a d j u s t m e n t t e c h n i q u e . L i s t e d a r e t h e v a l u e s o b t a i n e d when t h e p a t i e n t s t a r t e d t h e m a t c h w i t h t h e p u r e t o n e f r e q u e n c y a b o v e o r b e l o w t h a t o f t h e f u n d a m e n t a l o f t h e c o m p l e x . I n p a r e n t h e s e s i s t h e f r e q u e n c y v a l u e r e p r e s e n t i n g e i t h e r t h e f u n d a m e n t a l o f t h e c o m p l e x , i t s h a r m o n i c c o m p o n e n t s , o r o c t a v e s b e l o w h a r m o n i c s , w h i c h b e s t a p p r o x i m a t e t h e p i t c h v a l u e s . A d a s h e d l i n e r e p r e s e n t s no m a t c h . I l l P a t i e n t : R . L . P i t c h Match ing Procedure P . M . c o n t r o l P . M . c o n t r o l P . M . betw. P . M . betw. wi th no i se ears ears w. no i se P i t c h 309 310 301 313 va lue (300 - (300 - ( 300 - ( 300 -with f u n d . ) f u n d . ) fund . ) fund . ) s t a r t . f r e q . 582 588 311 313 above (600 - (600 - ( 300 - ( 300 -f u n d . 2nd h a r . ) 2nd har . ) f u n d . ) f u n d . ) (Hz) 591 591 565 318 (600 - (600 - (600 - (300 -2nd h a r . ) 2nd h a r . ) 2nd h a r . ) f u n d . ) 595 599 580 (600 - (600 - 586 2nd h a r . ) 2nd h a r . ) (600 -2nd har . ) 596 601 847 (600 - ( 600 - (900 -2nd h a r . ) 2nd h a r . ) 3rd h a r . ) P i t c h 308 579 300 313 va lue ( 300 - ( 600 - ( 300 - ( 300 -w i t h f u n d . ) 2nd har . ) f u n d . ) f u n d . ) s t a r t . f r e q . 580 580 307 315 below (600 - (600 - ( 300 - ( 300 -f u n d . 2nd har . ) 2nd har . ) f u n d . ) f u n d . ) (Hz) 580 581 586 316 (600 - (600 - (600 - (300 -2nd h a r . ) 2nd har . ) 2nd har . ) fund . ) 584 590 600 594 (600 - (600 -2nd h a r . ) 2nd h a r . ) 112 s t a r t i n g frequency of £2 was below the fundamental frequency of the complex. In spite of not matching to the fundamental, patient A.F. did match on two occasions to the octave above the fundamental. i i ) Pitch matching control with noise With the addition of low-pass f i l t e r e d noise to the complex test sound, both presented to the intact ear, patients A.D., L.F., and R.L. (tables 10, 13, and 14, respectively) were s t i l l able to match to the fundamental, although for patient R.L. this now occurred only when f2 was i n i t i a l l y presented above the fundamental of f l . Patient G.F. did not match even once to the fundamental (table 12). However, on every t r i a l he did match two octaves above the fundamental. S i m i l a r l y , patient A.F. who was s t i l l unable to match to the fundamental (table 11), matched three times to the octave above the fundamental. JJJJ Pitch matching between ears When the complex test sound was presented to the damaged ear and the comparison pure tone presented to the intact ear ( i . e . , pitch matching between ears) a l l patients were able to match at least once to the fundamental of the complex (tables 10 to 14). Thus, patient A.F. who was unable to match to the fundamental during the pitch matching 113 control procedure did so during the pitch matching between ears procedure when the pure tone frequency was i n i t i a l l y presented below that of the fundamental of the complex (table 11). The other patients matched to the fundamental at least once during both the pitch matching control and the pitch matching between ears procedures (tables 10, 12, 13, and 14). iv) Pitch matching between ears with noise Addition of low-pass f i l t e r e d noise to the complex test sound during the pitch matching between ears procedure resulted in at least one match to the fundamental of the complex for a l l patients except L.F. who reported d i f f i c u l t y defining any pitch (see tables 10 to 14). Patient A.D., who matched once to the fundamental during pitch matching between ears, matched twice to the fundamental when noise was presented along with the complex tone (table 10). Also, patient A.F., who matched to the fundamental during pitch matching between ears only when the pure tone frequency was i n i t i a l l y below that of the fundamental, matched to the fundamental when the pure tone was i n i t i a l l y presented above or below that of the fundamenatal after addition of noise (table 11). Better performances in the presence of noise were observed also in patient R.L. who matched to the fundamental six out of six times regardless of the i n i t i a l 114 frequency setting of the pure tone (see table 14). Patient G.F., who matched once to the fundamental during pitch matching between ears when the pure tone frequency was i n i t i a l l y set below that of the fundamental, matched to the fundamental after adding noise, but only when the pure tone frequency was i n i t i a l l y set above the fundamental (see table 12) . Table 15 summarizes the number of matches the patients made to either the fundamental and the octaves above and below the fundamental, or to the presented p a r t i a l s and their related octaves. The f i r s t group represents matches made in the "synthetic" mode of hearing as described by Terhardt (1972,1974,1978) since the fundamental was not phy s i c a l l y presented in the complex stimulus. The l a t t e r group represents matches made in the "analytic" mode of hearing also described by Terhardt, and represents matches based upon individual p a r t i a l s . Note that a match to the fourth harmonic of the fundamental ( i . e . , the second octave above the fundamental) was counted in both groups since i t not only represents octave confusion to the fundamental, but also was a physically presented p a r t i a l in the complex stimulus. The t o t a l number of t r i a l s was 48 for the two-alternative forced choice adaptive method, and 135 for the up-down adjustment technique. 115 Table 15: Summary of the number of matches the patients made to either the fundamental and the octaves above and below the fundamental, or to the presented p a r t i a l s and their related octaves. Matches to the fourth harmonic (second octave above the fundamental) were tabulated in both groups. n refers to the number of t o t a l patients. N.B.: Matching to octaves related to the fundamental were considered as evidence in support of the a b i l i t y to perceive the missing fundamental, and are therefore grouped together (see "discussion" for explanation). 116 Pitch Matching Technique Two-Alternative Forced Choice Adaptive Method n = 6 matches to the fundamental or i t s related octaves matches to the presented p a r t i a l s or their related octaves P.M. Procedure P.M. control 6 4 P.M. control 1 . 5 with noise P.M. between 4 3 ears P.M. between 2 4 ears with noise Up-Down Adjustment Technique n =5 matches to the fundamental or i t s related octaves matches to the presented p a r t i a l s or their related octaves P.M. control 23 11 P.M. control 24 9 with noise P.M. between 21 5 ears P.M. between 12 3 ears with noise 117 The table shows the following: 1) Using the two-alternative forced choice adaptive method, more matches were made to the fundamental or i t s related octaves as compared to matches to the presented p a r t i a l s or their related octaves, except in the presence of noise. 2) Using the two-alternative forced choice adaptive method, two more matches to the fundamental or i t s related ocataves were made during pitch matching control as compared to pitch matching between ears, but one more match was made during the l a t t e r procedure as compared to the former when noise was present. 3) The t o t a l number of matches during the two-alternative forced choice adaptive method was 29, thereby giving an overall match rate of 60% (29/48). 4) Using the up-down adjustment technique, two to four times as many matches were made to the fundamental or i t s related octaves as compared to matches to the presented p a r t i a l s or their related octaves, regardless of the pitch matching procedure. 5) Using the up-down adjustment technique, pitch matching control with noise and pitch matching between ears had l i t t l e e f f e c t on the t o t a l number of matches to the fundamental or i t s related octaves as compared to pitch matching control. 118 6) The t o t a l number of matches duri n g the up-down adjustment technique was 108, thereby g i v i n g an o v e r a l l match r a t e of 80% (108/135). The r e s u l t s can a l s o be summarized s l i g h t l y d i f f e r e n t l y by l o o k i n g o n l y at matches to the m i s s i n g fundamental or to the presented p a r t i a l s ( i . e . , harmonics 3 to 7, or 3 to 10). Table 16 shows the f o l l o w i n g : 1) Using the t w o - a l t e r n a t i v e f o r c e d choice adaptive method, the s y n t h e t i c mode of hearing was c l e a r l y dominant s i n c e a t o t a l of 10 matches were made to the fundamental, but none to the presented p a r t i a l s . 2) Using the t w o - a l t e r n a t i v e f o r c e d choice adaptive method, one more match to the fundamental occurred d u r i n g p i t c h matching c o n t r o l as compared to p i t c h matching between ears, but one more match was made d u r i n g the l a t t e r procedure as compared to the former when noise was present. 3) Using the t w o - a l t e r n a t i v e f o r c e d choice adaptive method, fewer matches were made to the fundamental dur i n g procedures with noise than without n o i s e . 4) The t o t a l number of matches d u r i n g the two-a l t e r n a t i v e f o r c e d choice adaptive method was 10, thereby g i v i n g an o v e r a l l match r a t e of 21% (10/48). 5) Using the up-down adjustment technique, the number of matches to the fundamental and to the presented p a r t i a l s was approximately the same du r i n g p i t c h matching c o n t r o l 119 TABLE 16: Summary of the number of matches the patients made to either the missing fundamental, or to the presented p a r t i a l s . n refers to the number of t o t a l patients. 120 P 1 tr.h Match 1 ng Tsnhn 1 qiift Two-Alternative Forced Choice Adaptive Method n = 6 matches to the fundamental matches to the presented part i a l s P.Mi F-CQC$d.u,ce. P.M. control P.M. control with noise 4 1 0 0 P.M. between ears P.M. between ears with noise Up-Down Adjustment Technique n =5 matches to the fundamental matches to the presented part i a l s P.M. control 9 8 P.M. control 6 8 with noise P.M. between 14 3 ears P.M. between 11 2 ears with noise 121 with or without noise, but matching to the fundamental was c l e a r l y dominant during pitch matching between ears regardless of noise. 6) The t o t a l number of matches during the up-down adjustment technique was 61, thereby giving an ov e r a l l match rate of 45% (61/135). 122 D I S C U S S I O N Previous studies investigating the perception of the lacking fundamental have used low frequency masking noise to eliminate d i s t o r t i o n products which could contribute to the percept (Moore,1973; Moore & Rosen, 1979). However, low ch a r a c t e r i s t i c frequency fibers maintain synchrony of neural discharges to signal waveforms even in the presence of noise (Kiang & Moxon,1974; Rhode et al.,1978; Sachs et al.,1983). Therefore, by using patients with u n i l a t e r a l low frequency hearing loss, pitch of the missing fundamental, and thus, pitch perception in general, was addressed in the absence of the contribution provided by low c h a r a c t e r i s t i c frequency f ibers . The results c l e a r l y indicate that the patients with low frequency hearing loss were able to match a complex tone to the lacking fundamental or i t s related octaves even though the fundamental f e l l within a damaged area along the basila r membrane innervated by nerve fibers with corresponding c h a r a c t e r i s t i c frequency. Using the up-down adjustment technique, the patients made four times as many matches to the missing fundamental and i t s related octaves as compared to the presented p a r t i a l s and their related octaves during pitch matching between ears with or without noise (see table 1 2 3 15) . When considering only matches to the fundamental or the presented p a r t i a l s ( i . e . , disregarding octave confusion), then this r a t i o increases to five (see table 16) . Neither the low-pass f i l t e r e d noise nor the fact that the complex tone was presented to the patient's damaged ear seemed to have affected their a b i l i t y to perceive the lacking fundamental. Performance was even improved during these procedures since only a two fold difference in the number of matches to the fundamental or i t s octaves as compared to the presented p a r t i a l s or their octaves occurred during the control procedures (table 15). Furthermore, when considering only matches to the fundamental or the presented p a r t i a l s , this r a t i o was one-to-one during the control procedures (table 16). Looking at the absolute number of matches to the fundamental using the up-down adjustment technique (table 16) also shows how matching to the residue was of greater ease during pitch matching between ears with and without noise (14 and 11 matches, respectively) as compared to pitch matching control with and without noise (9 and 6 matches, re s p e c t i v e l y ) . This a b i l i t y to perceive the missing fundamental or i t s related octaves demonstrates that the patients were able to perceive pitch using a "synthetic" mode of hearing as described by Terhardt (1972,1974,1978), that is to hear the complex stimulus as an e n t i t y rather than a n a l y t i c a l l y breaking i t down into i t s individual 124 components. The overall error rate during the up-down adjustment technique was 20% ( i . e . , match rate of 80%) when considering matches to the fundamental or i t s related octaves, and to the presented p a r t i a l s or their related octaves. When considering only matches to the fundamental and the presented p a r t i a l s , the error rate was 55% ( i . e . , match rate of 45%). These error rates do, however, indicate a good performance l e v e l in view of the following simple cal c u l a t i o n s . Since a precision factor of 1.125 above and below a target frequency was used to establish a match, the frequency range from 100 to 1130 Hz used in the up-down adjustment technique can thus be subdivided into approximately 10 contiguous precision bans, and the pr o b a b i l i t y of correct i d e n t i f i c a t i o n of the target frequency would be 1/10 or 10%. This would translate into an error rate of 90%. Clearly the observed error rates were considerably better, in spite of the d i f f i c u l t i e s of the tasks. One d i f f i c u l t y was the requirement to match a pure tone to a complex tone. Due to the d i f f e r e n t timbres of these two s t i m u l i , i t can be very d i f f i c u l t to compare pitches when the tones are presented in i s o l a t i o n (rather than in the context of a melody). Nonetheless, the use of a comparison pure tone rather than a complex tone was 125 desirable in these experiments in order to investigate whether the a b i l i t y to hear pure tones at the fundamental was necessary to perceive the missing fundamental. Furthermore, octave confusion made i t d i f f i c u l t for patients to match prec i s e l y to the fundamental. This was expected since the complex tone is dominated by the octave when compared with other musical i n t e r v a l s . It is generally easier to i d e n t i f y a musical interval than absolute fundamental frequency between two tones. The "octave i l l u s i o n " (Duetsch,1974a,b,1975) is a phenomenon whereby two presented notes an octave apart alternating between ears is perceived in each ear as either one of the two notes. Perception of a note an octave above or below a presented note could therefore be attributed to "perception" of that presented note. Thus, matching to octaves related to the fundamental can be considered as evidence in support of our a b i l i t y to perceive the missing fundamenatal. The results from the two-alternative forced choice adaptive method did not i l l u s t r a t e to the same extent, in absolute number of matches, the a b i l i t y to perceive the missing fundamental as compared to the up-down adjustment technique, regardless of the procedure. Also, overall match rates were about 20% lower during the forced choice adaptive method as compared to the adjustment technique. However, because the patients were not r e s t r i c t e d to pitch match 126 within a frequency range as In the up-down adjustment-technique, the entire auditory frequency range (20 Hz to 16 kHz) was av a i l a b l e . Using the same precision factor as in the up-down technique, t h i s range can be subdivided into approximately 30 contiguous precision bands, 1 and the p r o b a b i l i t y of correct i d e n t i f i c a t i o n of the target frequency would be 1/30 or 3%. This would translate into an error rate of 97% for the two-alternative forced choice adaptive method, as opposed to 90% for the up-down adjustment technique. In spite of the d i f f i c u l t y of the task, there were s t i l l more matches to the fundamental and i t s octaves as compared to matches to individual components and their octaves during pitch matching control and pitch matching between ears (see table 15), thereby strengthening the aforementioned conclusions. Furthermore, when considering only matches to the fundamental or to presented p a r t i a l s (see table 16), the synthetic mode of hearing was c l e a r l y dominant in a l l procedures as there were no matches at a l l to the presented p a r t i a l s , but at least one match to the fundamental in a l l procedures. The addition of noise made i t more d i f f i c u l t to perceive the lacking fundamental using t h i s technique (tables 15 and 16), but the fact that matches were made to the fundamental, regardless of the number, demonstrates that perception of the missing fundamental did indeed occur. 127 It is interesting to note that the best performers with regard to matching to the fundamental or i t s related octaves were those patients with musical t r a i n i n g (L.F. and R.L.), suggesting that the ease to which we are able to perceive the lacking fundamental is d i r e c t l y related to our musical experience. The question that arises from these studies is the following: How are those patients able to perceive the pitch of the missing fundamental when no pitch cues are transmitted via the low c h a r a c t e r i s t i c frequency f i b e r s ; those fibers whose place of innervation along the basilar membrane corresponds to the place of maximal displacement when stimulated by sound waves with frequency corresponding to that of the fundamental? One possible explanation is that since the patients used in this study did not have absolute low frequency loss, i t might have been possible that enough information was conducted along those low c h a r a c t e r i s t i c frequency fibers to the central nervous system enabling them to perceive the pitch of the missing fundamental. Even though a combination tone generated from the components of the complex, whose frequency corresponded to the fundamental, probably would not have been of s u f f i c i e n t i n t e n s i t y to stimulate those low frequency fibers innervating the damaged region of the cochlea, the p o s s i b i l i t y should not be ruled out that a 128 sufficient- number of fibers innervating p a r t i a l l y damaged areas with hearing thresholds low enough to be stimulated could conduct the necessary pitch cues. However, i f information pertaining to the pitch of the missing fundamental was carried in the low c h a r a c t e r i s t i c frequency f i b e r s , how was i t possible for the patients to perform as well as, or even better, when the complex test sound was presented to the damaged ear as compared to the intact ear? Many studies have been done on the effects of hearing impairment upon frequency discrimination. Zurek & Formby (1981) attempted to determine how the a b i l i t y to detect a change in the frequency of a pure tone is affected in subjects with sensorineural hearing loss. They showed that the a b i l i t y of hearing-impaired l i s t e n e r s to detect a pure tone frequency change was more disrupted for low frequency tones than for high frequency tone's, given the same degree of hearing loss at the test frequency. This finding can be explained by the asymmetrical spread of excitation in the cochlea. A low frequency tone has a maximum excitation pattern at the apex of the basi l a r membrane, but extends broadly to a lesser extent through the middle and basal cochlear regions. Therefore, a given amount of damage in the apical region of the cochlea may result in a smaller threshold s h i f t because of the excitation in the more basal 129 areas. Thus, Zurek & Formby propose that at low frequencies a given threshold s h i f t may indicate more damage than at higher frequencies. Therefore r e l a t i v e l y large changes in frequency discrimination at low frequencies would be associated with small changes in hearing threshold. Goldstein & Srulovicz (1977) and Srulovicz & Goldstein (1983) have shown that mathematical modeling of auditory-nerve fiber interspike intervals can predict the frequency discrimination of pure tones. Their model implies that impaired phase-locking a b i l i t y in damaged cochleas would result in a deterioration of frequency discrimination. They imply that frequency discrimination is based primarily on temporal aspects of s i n g l e - f i b e r a c t i v i t y . The results of Zurek & Formby suggest that the patients with low frequency hearing loss, investigated ln this study, have suffered a far more extensive loss of hair c e l l s and/or neurons along a greater extent of the basilar membrane than their audiograms would imply. This would res u l t in a considerable deterioration of phase-locking for fibers with low (and also higher) c h a r a c t e r i s t i c frequencies. Perhaps the deterioration of the temporal code is more severe in these cases than that of the s p a t i a l code. Since the data do not suggest that the perception of the lacking fundamental via the damaged ears was i n f e r i o r when compared with the intact ears, i t seems highly u n l i k e l y that the 130 fundamental frequency could have been mediated by either a s p a t i a l or a temporal code in the low c h a r a c t e r i s t i c frequency f i b e r s . Other investigators have found that the hearing impaired have a d e f i c i t in their frequency resolution (Hoekstra, 1 9 7 9 ; Glasberg & Moore, 1 9 8 6 ; Moore & Glasberg,1986a,b; Tyler & Tye-Murray,1986). This refers to the a b i l i t y to detect, a sound of one frequency as d i s t i n c t in the presence of another with a d i f f e r e n t frequency. Impaired resolution has been found to res u l t in a deterioration in the a b i l i t y to extract pitch information (Evans,1978a), and to lead to poor speech perception (Scharf,1978; Florentine et al.,1980). In addition, hearing-impaired l i s t e n e r s perform poorly in temporal resolution tasks as, for example, in gap detection (Irwin et al.,1981; Fitzgibbons & Wightman,1982; Irwin & McAuley,1987; Glasberg et al.,1987; Moore & Glasberg,1988). Impaired temporal processing may contribute to poof speech perception in patients with hearing loss (Tyler et al.,1982; Dreschler & Plomp, 1985). Also, improved hearing in patients with cochlear implants has been shown to depend on their temporal (gap detection) acuity (Hochmair-Desoyer et al.,1984). Other evidence suggests there is a reduction in the synchrony of the discharge from Vlllth-nerve fibers that innervate the region of hearing loss (Wakefield & 1 3 1 Nelson,1985), and that this reduction is responsible for the impaired frequency resolution (Woolf et al.,1981). Furthermore, studies involving loudness summation have suggested that the c r i t i c a l band is affected in cochlear impairment (Scharf & Hellman,1966; Martin,1974; Bonding,1979). C r i t i c a l bands are compared to an internal acoustic f i l t e r system which s p l i t s the acoustical i n t e n s i t y into contiguous frequency bands. C o l l e c t i v e l y then, i t appears that the patients in the present experiment should have experienced greater d i f f i c u l t y in pitch matching to the missing fundamental in the diseased ear than in the intact ear i f the frequency signals corresponding to the pitch were orig i n a t i n g in cochlear nerve fibers with c h a r a c t e r i s t i c frequencies corresponding to the fundamental. As this was not the case in the present study, the above assumption regarding the conduction of pitch cues along the low c h a r a c t e r i s t i c frequency fibers remains doubtful. Another possible Interpretation of the present results is that the spread of excitation towards the base, generated by the cubic difference tone, could be responsible for pitch cues carried in the f i r s t higher frequency fibers innervating a normal hearing threshold area. Whether these higher frequency fibers are capable of conveying information regarding the missing fundamental is debatable. 132 in 1950, Davis et a l . shoved that subjects with u n i l a t e r a l noise-induced hearing loss, when matching pure tones between ears, showed large upward displacements of pitch by as much as three-quarters of an octave. Similar findings have also been demonstrated in patients with u n i l a t e r a l Meniere's disease (Jones & Pracy,1971). The explanation of this upward s h i f t in pitch was attributed to ch a r a c t e r i s t i c s of the sensory units of the auditory nerve. Because s e n s i t i v i t y of nerve fibers f a l l s off rapid l y as the frequency is increased from i t s c h a r a c t e r i s t i c frequency, and slowly as the frequency is decreased, a given frequency would then excite more e a s i l y sensory units that are tuned to higher frequencies much more so than those tuned to lower frequencies. These studies, involving u n i l a t e r a l hearing loss and the upward displacement of pure tone pitch, again indicate that the missing fundamental pitch heard by patients in the present study was not due to peripheral excitation by the fundamental frequency. The f i r s t higher frequency fibers available basal to the damaged region innervated by the low frequency fibers should have been excited, and an upward s h i f t in pitch should have occurred. This was not evident in the present study. The most probable explanation regarding the a b i l i t y of the patients in the present study to perceive the missing 133 fundamental does not depend on the generation of combination tones, but involves the conduction of pitch cues along those neural fibers whose c h a r a c t e r i s t i c frequencies correspond to the actual presented component stimuli contained within the complex. The concept of a dominant frequency region for pitch information was introduced by Ritsma (1967a,b,1970) and Bilsen & Ritsma (1967). It was found that for fundamental frequencies in the range 100 to 400 Hz, the frequency band containing the t h i r d , fourth, and f i f t h harmonics dominated the pitch percept. Thus the dominance region is the spectral region of three to five times the frequency of the perceived p i t c h . A l l complexes presented in the present study contained the t h i r d , fourth, and f i f t h harmonics, and in addition, the fundamental frequencies chosen were within the 100 to 400 Hz range with the exception of 700 Hz which was used for patient J.W. This patient did pitch match once to the lacking fundamental. Therefore, for a l l but one patient, harmonic components and the frequency range of the missing fundamental that were used in this study f i t the c r i t e r i a necessasry for optimal extraction of the lacking fundamental. Other work by M i l l e r & Sachs (1984) showed that responses of auditory nerve fibers to a voiced stimulus were 134 dominated by harmonics of the fundamental frequency. It was found that the pitch-related harmonic structure within the spectrum was preserved in the ALSR in that the voice pitch was represented by peaks in the temporal responses at harmonic places in the nerve f i b e r s . These findings support the p o s s i b i l i t y that the auditory fibers responding to the component stimuli of a complex sound could have signaled in their response pattern p e r i o d i c i t i e s the necesssary information to perceive the missing fundamental in patients with ear damage to the low c h a r a c t e r i s t i c frequency regions. More supporting evidence comes from several investigators interested in brainstem responses to auditory stimuli who evaluated the relationship between the frequency-following response (FFR) recorded from humans and the low pitch of complex tones (Smith et al.,1978; Greenberg & Marsh,1979,1980; Greenberg et al.,1987). It has been suggested that the neural events which generate the FFR result from a c o l l e c t i o n of the individual a c t i v i t y of a group of phase-locking neurons within the brain stem auditory nuclei (Smith et al.,1975; Sohmer et al. 71977; Gardi et al. 71979). Bojanowski et a l . (in press) have, in fact, recorded corresponding microphonic potentials in the medial superior o l i v e . Smith et a l . (1978) and Greenberg et a l . (1987) found that the FFR to harmonic signals with an 135 absent fundamental frequency was similar to that generated by pure tones equal to the lacking fundamental of the complex s t i m u l i . The l i k e l i h o o d that the FFR to the missing fundamental was a product of nonlinear d i s t o r t i o n in the periphery was ruled out since the FFRs to the pure tone and the complex tone of equivalent fundamental frequency d i f f e r e d in response latency and amplitude. Furthermore, although the amplitude of the FFR to the pure tone was greatly reduced by low-frequency band-passed noise centered at the frequency of the lacking fundmental, the amplitude of the FFR to the complex tone was r e l a t i v e l y unaffected by the noise . With regard to the existence of the dominant region of the residue, Greenberg & Marsh (1979) and Greenberg et a l . (1987) found that the magnitude of the FFR to the fundamental was greatest when generated by the t h i r d to the f i f t h harmonics. The amount of energy in th i s frequency band dissipated with increasing harmonic number and was v i r t u a l l y absent for harmonics eight and nine. Because the f i r s t and second harmonics by themselves did not generate a large FFR, this further suggests that d i s t o r t i o n products generated at the tonotopic location corresponding to the residue were not responsible for the responses. Frequency regions that generated the largest FFR were between 500 and 1000 Hz which are consistent with the 136 frequencies suggested by Ritsma (1967b) generating the strongest pitch . Since this is also the frequency region where the most precise phase-locking occurs (Johnson,1980), Greenberg et a l . (1987) suggest that the magnitude of the FFR r e f l e c t s the precision of synchronized a c t i v i t y to the stimulus frequencies. It is interesting to note that the FFRs of the largest magnitude are generated by complexes whose fundamental f a l l s between 100 and 500 Hz, and are v i r t u a l l y non-existent beyond fundamentals of 1 kHz (Greenberg,1980). The fundamentals chosen in the present experiments were 200, 300, and 700 Hz. Patient J.W., whose presented complex had a fundamental frequency of 700 Hz, was only able to match once to the lacking fundamental. A 700 Hz fundamental f a l l s within a non-optimal frequency area for FFR generation. In addition, the lowest frequency component within that complex was 2100 Hz; outside the optimal 500 to 1000 Hz range found by Greenberg et a l . As suggested by the FFR studies, i f the synchronized a c t i v i t y is r e f l e c t e d in the FFR, then patient J.W.'s d i f f i c u l t y in perceiving the residue pitch may have resulted from a lack of synchronization within the neural f ibers . It has recently become possible to apply the underlying neural mechanisms of theore t i c a l pitch perception models by d i r e c t l y stimulating the auditory nerve in a controlled and 137 l o c a l i z e d manner. Deaf subjects have been implanted with intracochlear electrode devices in an attempt to bypass their destroyed hair c e l l s . With multiple electrodes implanted at various locations along the cochlea, investigators have found that patients can make pitch judgments corresponding to the cochlear place stimulated (House,1976; Eddington et al.,1978a,b; Townshend et al.,1987), and discriminate pairs of simple speech sounds (Eddington,1980). However, even with just a single electrode on the surface of the cochlea, patients are able to detect changes in the frequency of e l e c t r i c a l stimulation (Merzenich et al.,1973; House,1976; Douek et al.,1977; Fourcin et al.,1978; Townshend et al.,1987), can perform pitch scaling exercises over a several hundred hertz frequency range (Merzenich et al.,1973), and can accurately judge melodic intervals (Eddington et a l . , 1978b; Rosen et a l . , 1978 ). With only a single electrode used, the place of stimulation remains the same for a l l stimulating frequencies, hence these a b i l i t i e s are dependent on temporal information (Moore & Rosen,1979). 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