Clinical Psychoacoustics Laboratory

Auditory Analysis and Sensorineural Hearing Loss

Auditory analysis is the process by which the auditory system and the brain analyze sound into meaningful and useful codes. Usually this involves a frequency analysis of the time waveform into resolvable intensity changes within separate frequency channels as a function of time. Research is aimed at determining the limitations in auditory analysis that are associated with sens orineural hearing loss, to discover the mechanisms of peripheral processing that are most affected by cochlear pathology, and to develop ways of assessing the effects of cochlear pathology on auditory analysis.
This research is funded by grant R01-DC00149 awarded to David A. Nelson, Ph.D.,
by the National Institute of Deafness and Communication Disorders.
This research also receives local funding from the Lions 5M International Hearing Foundation.


Relevant Publications:

(with links to abstracts and html/pdf reprints or preprints)

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Wojtczak, M., Schroder, A.C., Kong, Y-Y. and Nelson, D.A. (1999). "Effect of BM compression on masking period patterns (MPPs)." Oral paper given to the 138th Acoustical Society of America, Columbus, Ohi o. November 2. J. Acoust. Soc. Am., 106, 2147 (A).

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Nelson, D.A. and Schroder, A.C. (1999). "Forward masking recovery and peripheral compression in normal-hearing and cochlear-impaired ears." Oral paper given to the 138th Acoustical Society of America , at the session honoring the contributions of Robert C. Bilger: "Bilger and Better Science". Columbus, Ohio. November 2. J. Acoust. Soc. Am., 106, 2176 (A).

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NELSON, D.A. and SCHRODER, A.C. (1997). "Linearized response growth inferred from growth-of-masking slopes in ears with cochlear hearing loss." J. Acoust. Soc. Am., (submitted June, 1996, revised 9/25/96, 11/20/96).

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NELSON, D.A. and SCHRODER, A.C. (1996). "Release from upward spread of masking in regions of high-frequency hearing loss," J. Acoust. Soc. Am.,100, 2266-2277.

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NELSON, D.A. and SWAIN, A.C. (1996). "Temporal resolution within the upper accessory excitation of a masker," Acustica, 82, 328-334.

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NELSON, D.A. and SCHRODER, A.C. (1995). "Critical bandwidth for phase discrimination in hearing-impaired listeners," J. Acoust. Soc., 98, 1969-1976.

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SCHRODER, A.C., VIEMEISTER, N.F. and NELSON, D.A. (1994). "Pure-tone intensity discrimination in hearing-impaired and normal-hearing listeners," J. Acoust. Soc. Am., 96, 2683-2693.

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NELSON, D.A. (1994). "Level dependent critical bandwidth for phase discrimination," J. Acoust. Soc. Am., 95, 1514-1524

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NELSON, D.A. (1991). "High-level psychophysical tuning curves: forward masking in normal-hearing and hearing- impaired listeners", J. Speech Hearing Res., 34, 1233-1249.

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FREYMAN, R.L. and NELSON, D.A. (1991). "Frequency discrimination as a function of signal frequency and level in normal-hearing and hearing-impaired listeners," J. Speech Hearing Res., 34, 1371-1386.

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NELSON, D.A. and FORTUNE, T.W. (1991b). "High-Level psychophysical tuning curves: simultaneous masking with different noise bandwidths", J. Speech Hearing Res., 34, 374-378.

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NELSON, D.A. and FORTUNE, T.W. (1991a). "High-Level psychophysical tuning curves: simultaneous masking by pure tones and 100-Hz wide noise bands", J. Speech Hearing Res., 34, 360-373.

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NELSON, D.A., CHARGO, S.J., KOPUN, J.G., and FREYMAN, R.L. (1990). "Effects of stimulus level on forward-masked psychophysical tuning curves in quiet and in noise," J. Acoust. Soc. Amer., 88, 2143-2151.

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NELSON, D.A. and PAVLOV, R. (1989). "Auditory time constants for off-frequency forward masking in normal- hearing and hearing-impaired listeners", J. Speech Hearing Res., 32, 298-306.

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KIMBERLEY, B.P., NELSON, D.A., and BACON, S.P. (1989). "Temporal overshoot in simultaneous-masked psychophysical tuning curves from normal and hearing-impaired listeners", J. Acoust. Soc. Amer., 85, 1660-1665.

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FREYMAN, R.L. and NELSON, D.A. (1987). "Frequency discrimination for short- vs long-duration tones by normal and hearing-impaired listeners," J. Speech Hearing Res., 30, 28-36.

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NELSON, D.A. and FREYMAN, R.L. (1987). "Temporal resolution in sensorineural hearing-impaired listeners," J. Acoust. Soc. Am., 81, 709-720.

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FREYMAN, R.L. and NELSON, D.A. (1986). "Frequency discrimination as a function of tonal duration and excitation-pattern slopes in normal and hearing-impaired listeners," J. Acoust. Soc. Amer., 79, 1034-1044.

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NELSON, D.A. and FREYMAN, R.L. (1986). "Psychometric functions for frequency discrimination from listeners with sensorineural hearing loss," J. Acoust. Soc. Amer., 79, 799-805.

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WAKEFIELD, G.A. and NELSON, D.A. (1985). "Extension of a temporal model offrequency discrimination: Intensity effects in normal and hearing-impaired listeners," J. Acoust. Soc. Amer., 77, 613-619.

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NELSON, D.A. and FREYMAN, R.L. (1984). "Broadened forward-masked tuning curves from intense masking tones: delay-time and probe-level manipulations," J. Acoust. Soc. Amer. 75, 1570-1577.

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NELSON, D.A., STANTON, M.E. and FREYMAN, R.L. (1983). "A general equation describing frequency discrimination as a function of frequency and sensation level," J. Acoust. Soc. Amer., 73, 2117-2123.

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TURNER, C.W., BURNS, E.M. and NELSON, D.A. (1983). "Pure-tone pitch perception and low-frequency hearing loss," J. Acoust. Soc. Amer., 73, 966-975.

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CARNEY, A.E. and NELSON, D.A. (1983). "An analysis of psychophysical tuning curves in normal and pathological ears," J. Acoust. Soc. Amer., 73, 268-278.

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SANTI, P.A., RUGGERO, M.A., NELSON, D.A. and TURNER, C.W. (1982). "Kanamycin and bumetanide ototoxicity: Anatomical, physiological and behavioral correlates," Hearing Res., 7:261-279.

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STANTON, M.E. and NELSON, D.A. (1982). "Frequency discrimination at 1200 Hz in the presence of high- frequency masking noise," J. Acoust. Soc. Amer., 71, 660-664.

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TURNER, C.W. and NELSON, D.A. (1982). "Frequency discrimination in regions of normal and impaired sensitivity," J. Speech Hearing Res., 25:34-41.

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NELSON, D.A. (1980). "Comment on: 'The use of psychophysical tuning curves to measure frequency selectivity'," (D.L. Weber, D. Johnson-Davies and R.D. Patterson). In Psych. Physiol. and Behav. Studies in Hearing. G. van den Brink and F.A. Bilsen (eds.), Delft University Press, p. 116.

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NELSON, D.A. and TURNER, C.W. (1980). "Decay of masking and frequency resolution in sensorineural hearing-impaired listeners," In Psych. Physiol.and Behav. Studies of Hearing. G. van den Brink and F.A. Bilsen (eds.) Delft University Press, pp. 175-182.

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NELSON, D.A. (1979). "Two-tone masking and auditory critical bandwidth," Audiology 18, 279-306.

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NELSON, D.A. and KEISTER, T.E. (1978). "Frequency discrimination in the chinchilla," J. Acoust. Soc. Amer. 64, 114-126.

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NELSON, D.A., KIESTER, T.E., TURNER, C.W. and WARD, W.D. (1977). "Automated conditioned-avoidance audiometry in the chinchilla," J. Aud. Res., 16:193-221.

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NELSON, D.A. and BILGER, R.C. (1974). "Octave masking in normal hearing listeners," J. Speech Hearing Res., 17(2):223-251.

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NELSON, D.A. and BILGER, R.C. (1974). "Octave masking in listeners with sensorineural hearing loss," J. Speech Hearing Res., 17(2):252-278.

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Effect of BM compression on masking period patterns (MPPs).

Wojtczak, M., Schroder, A.C., Kong, Y-Y. and Nelson, D. A. (1999). J. Acoust. Soc. Am., 106, 2147(A). Oral paper given to the 138th Acoustical Society of America, Columbus, OH, November 2.

MPPs were measured in listeners with normal and impaired hearing using tonal 4-Hz SAM maskers and short tonal probes with frequencies that were either identical to or higher than the carrier frequency of the masker. The probe frequencies were 500, 1200, and 3000 Hz for on-frequency masking, and 1200, 2400, and 6000 Hz for off-frequency masking. In normal-hearing listeners MPPs measured with off-frequency probes had valleys that were much longer and deeper than valleys observed with on-frequency probes. A similar result was observed in hearing-impaired listeners in the frequency region of mild hearing losses, where significant residual compression was presumably operating. However, in the frequency region with substantial hearing loss where compression is substantially reduced or absent, MPPs measured with the on- and off-frequency probes were very similar. A model consisting of peripheral filtering, compressive nonlinearity, and a sliding temporal window was used in an attempt to predict the data and to estimate the compression index. The results suggest that the similarity of on- and off-frequency temporal resolution in hearing-impaired listeners may be due in part to the lack of the compressive nonlinearity that is evident at the level of the basil ar membrane in normal-hearing listeners. [Work supported by NIH-NIDCD grant DC00149 and the Lionís 5M International Hearing Foundation.]

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Forward Masking Recovery and Peripheral Compression in Normal-Hearing and Cochlear-Impaired Ears.

Nelson, D. A. and Schroder, A.C. (1999). Oral paper given to the 138th Acoustical Society of America, Columbus, OH, November 2. Session honoring the contributions of Robert C. Bilger: "Bilger and Better Science".

Iso-response temporal masking curves were obtained from normal-hearing subjects at a probe frequency of 1000 Hz for masker frequencies between 500 and 1200 Hz. Time constants calculated from the temporal masking curves varied with masker frequency, from around 70 ms for low off-frequency maskers (500-600 Hz) to around 36 ms for on-frequency maskers (close to the probe frequency). Continuing Bilgerís earlier pursuits of nonlinearities in hearing, estimates of peripheral compression were calculated under the assumption that the response to a low off-frequency masker is linear at the probe frequency place. Average compression exponents varied from close to 1.0 for remote off-frequency maskers (both below and above the probe) to below 0.4 for on-frequency maskers. Input-output transfer functions derived from the compression exponents were consistent with BM transfer functions recorded in animals with normal cochlear function. Comparisons of iso-response temporal masking curves in subjects with sizable co chlear hearing losses at the probe frequency yielded linear transfer functions consistent with BM data from cochlear-damaged animals. It is concluded that time constants for recovery from forward masking in ears with cochlear hearing loss are no differen t than those obtained from normal-hearing ears, once differences in peripheral compression are taken into account. [Work supported by NIH-NIDCD grant DC00149 and the Lionís 5M International Hearing Foundation.]

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Linearized response growth inferred from growth-of-masking slopes in ears with cochlear hearing loss

Nelson, D.A. and Schroder, A.C. (1997). J. Acoustical Society of America, 101, 2186-2201.

Growth of masking for OFF-frequency conditions (probe frequency above the masker spectrum) and ON-frequency conditions (probe within the masker spectrum) was investigated using simultaneous masking in three subjects with normal hearing and nine subjects w ith high-frequency sensorineural hearing loss. Growth-of-masking functions (probe thresholds as a function of masker intensity) for OFF-frequency conditions were obtained for probe tones placed at six frequencies above a 200-Hz wide masker with an upper edge at 520 Hz. Growth-of-masking functions for ON-frequency conditions were obtained for probe tones placed within the 200-Hz wide masker and for probe tones placed within 400-Hz wide maskers with upper edges at 1040, 1300, 1627 and 2040 Hz (probe tones placed 20 Hz below the upper edge frequency). Growth-of-masking functions were fit with a power function of masker intensity added to an internal noise with intensity equal to the absolute threshold for the probe, and were well described by two free par ameters and a threshold constant: the growth-of-masking slope (B), a masking sensitivity constant (K) that indicated the minimum effective masker level at which masking began, and the intensity of the probe at absolute threshold (It). For O FF-frequency masking conditions, growth-of-masking slopes (B) decreased by a factor of 0.8 for every 10 dB of hearing loss. Comparisons with data from previous studies of upward spread of masking, and assumptions about underlying physiological mec hanisms, led to the conclusion that more gradual than normal growth-of-masking slopes reflect larger (steeper) growth-of-response slopes at the probe frequency in regions of hearing loss. Derived response-growth exponents increased by a factor of 1.2 for every 10 dB of hearing loss, from an exponent around 0.25 at 0 dB HL to an exponent around 1.0 at 75 dB HL (linear response growth). Masking sensitivity constants (K), the minimum effective masker levels, indicated that masking began at slightly higher masker levels in subjects with sensorineural hearing loss than in subjects with normal hearing. It was concluded that higher masked thresholds in regions of hearing loss were due primarily to a loss of active gain at the probe frequency and were n ot due to an excessive response at the probe frequency to the lower-frequency masker. For ON-frequency masking conditions, growth-of-masking slopes were not different from normal in hearing-impaired subjects. ON-frequency masking began when the effectiv e power within an auditory filter at the probe frequency reached elevated absolute threshold at the probe frequency. Critical ratios were normal except for one subject with the most hearing loss.

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Release from upward spread of masking in regions of high-frequency hearing loss

Nelson, D.A. and Schroder, A.C. (1996). J. Acoustical Society of America, 82, 328-334.

Upward spread of masking was compared for 500-Hz quasi-frequency-modulated (QFM) and sinusoidally-amplitude-modulated (SAM) maskers. Modulation rate was 20 Hz, which resulted in maskers with identical long-term spectra but a relatively flat temporal envel ope for the QFM masker and a fluctuating temporal envelope for the SAM masker. At signal frequencies more than an octave above the masker, masked thresholds for the SAM masker were lower than for the QFM masker, revealing “masking release” (QFM- SAM masked threshold differences) exceeding 30 dB in normal-hearing ears. In ears with high-frequency sensorineural hearing loss, but normal hearing in the region of the masker, masking release was markedly reduced or completely absent in regions of heari ng loss. The data were evaluated with a model of masking based on the linearized response growth (LRG) of basilar membrane transfer functions associated with cochlear damage in animals. The LRG model predicted more gradual slopes of the growth of masking and reduced masking in regions of hearing loss. The reduced masking release seen in regions of hearing loss could be largely accounted for by a more rapid growth of response to the probe tone in regions of hearing loss.
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Temporal Resolution Within the Upper Accessory Excitation of a Masker

Nelson, D.A. and Swain, A.C. (1996). Acustica, 82, 328-334.

Professor Eberhard Zwicker [1] observed that the dynamic range of masking period patterns for amplitude-modulated maskers was larger for frequencies above the masker (in the upper "accessory excitation" where no physical masker energy exists) than for fre quencies near the masker (in the "main excitation" where masker energy exists), which implies that temporal resolution of acoustic envelopes is substantially better within the upper accessory excitation than in the main excitation. His finding has signifi cant implications for speech perception in fluctuating-masker environments, but unfortunately it has received little attention since his original report. The present research investigated temporal envelope resolution in normal-hearing subjects by measurin g masking at the peaks and valleys of a 500-Hz 100% amplitude-modulated tonal masker as a function of test frequency and stimulus level. Modulation rate was 4 Hz. Masked thresholds were measured using amplitude-modulated signals with envelope peaks that corresponded with envelope peaks and valleys of the masker. The results confirmed Zwicker's earlier observation. Peak-to-valley masked-threshold ratios averaged 14. 4 dB for signals within the main excitation, compared to average ratios as large as 33.4 dB within the upper accessory excitation. Slopes of the growth of masking support the interpretation that masking during envelope peaks is associated with simultaneou s masking, for both the main excitation and the upper accessory excitation. Masking during envelope valleys appears to be determined by non-simultaneous masking in the upper accessory excitation, but behaves more like simultaneous masking in the main exci tation of the masker.

[1] Zwicker, E., Mithörschwellen-Periodenmuster amplitudenmodulierter Töne (Masking-period patterns of amplitude modulated pure tones). Acustica, 36, [1976], 113-120.

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Critical Bandwidth for Phase Discrimination in Hearing-Impaired Listeners

Nelson, D.A. and Schroder, A.C. (1995). Journal of the Acoustical Society of America, 98, 1969-1976.

Monaural phase discrimination was evaluated in normal-hearing and hearing-impaired listeners as a function of the frequency separation among components in three-tone complexes. The phases of the center components of 100% sinusoidal amplitude-modulated (S AM) waveforms were shifted by 90° to yield quasi-frequency-modulated (QFM) waveforms that had identical long-term spectra but different envelopes and temporal fine structure. Normal-hearing listeners can distinguish QFM waveforms from SAM waveforms as long as the modulation frequency (frequency separation between components) is less than about 40% of the carrier frequency (center component). Phase discrimination performance (d') was measured as a function of modulation frequency, and critical bandw idths for phase discrimination (CBphs) were specified as the modulation frequency corresponding to a performance index (d') of 1.0. In normal-hearing ears, CBphs increased with stimulus SPL. In hearing-impaired ears, CBphs estimates were equal to or nar rower than normal when comparisons were made at the same SPLs; CBphs estimates from hearing-impaired ears were broader (better) than normal only when comparisons were made at equivalent SLs. Differences between CBphs estimates in normal-hearing and hear ing-impaired ears are explained by level-dependent auditory filtering and the sensation levels at which comparisons are made, without the necessity to postulate abnormal tuning in hearing-impaired ears.
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Pure-tone intensity discrimination in hearing-impaired and normal-hearing listeners

Schroder, A.C., Viemeister, N.F. and Nelson, D.A. (1994). Journal of the Acoustical Society of America, 96, 2683-2693.

Weber fractions (delta-I/I) for gated 500-ms tones at 0.3, 0.5, 1, 2 and 3 kHz, and at levels of the standard ranging from absolute threshold to 97 dB SPL, were measured in quiet and in highpass noise in five listeners with cochlear hearing loss and in th ree normal-hearing listeners. In regions of hearing loss, the Weber fractions at a given SPL were sometimes normal. When the Weber fractions were normal or near-normal, the addition of highpass noise elevated the Weber fraction, strongly suggesting the use of spread of excitation to higher frequencies. Inversely, when the Weber fractions were elevated, the addition of highpass noise produced no additional elevation, suggesting an inability to use spread of excitation. In general, the relative size of the Weber fractions, the effects of highpass noise, and, to a lesser extent, the dependence of the Weber fraction on level, were consistent with expectations based upon the audiometric configuration and the use of excitation spread. There were several no table inconsistencies, however, in which normal Weber fractions were seen at a frequency on the edge of a steep high-frequency loss, and in which elevated Weber fractions were seen in a flat audiometric configuration. Finally, when compared at the same S L, the Weber fraction was sometimes smaller in cochlear-impaired than in normal hearing listeners. This was true even in highpass noise, where excitation spread was limited, and may reflect the unusually steep rate-level functions seen in auditory nerve fibers that innervate regions of pathology.
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Level Dependent Critical Bandwidth for Phase Discrimination

Nelson, D.A. (1994). Journal of the Acoustical Society of America, 95, 1514-1524.

Monaural phase discrimination was evaluated at 1000 Hz in six normal-hearing listeners as a function of the frequency difference between components in three-tone complexes at 40, 60, 80 and 100 dB SPL. The phase of the center component of 100% sinusoidal ly amplitude-modulated (SAM) waveforms was shifted by 90° to produce quasi-frequency-modulated (QFM) waveforms that had identical long-term power spectra to the SAM waveforms but with different amplitude envelopes and temporal fine structure. At low modulation frequencies, where spectral components were close together and well within a single auditory filter, normal-hearing listeners could easily discriminate QFM from SAM waveforms. As modulation frequency increased, a point was reached where QFM c ould no longer be distinguish from SAM, which is referred to here as the critical bandwidth for phase discrimination (CBphs). Discrimination performance (d') was measured as a function of modulation frequency to yield psychometric functions for phase dis crimination, from which CBphs values were defined as the modulation frequency corresponding to d'=1.0. At a carrier frequency of 1000 Hz, CBphs increased with level between 40 and 80 dB SPL according to the following relation: CBphs = 34( I )0.136. Above 80 dB SPL, very little change in CBphs with level was seen. The increase in CBphs with level was predicted from level-dependent auditory filter slopes inferred from forward-masked tuning curves, a s was the tendency to reach an asymptote above 80 dB SPL. Comparisons with previous work indicate that CBphs values from the best performing subjects were well within the audibility region for cubic difference tones. It is proposed that internally gener ated cubic difference tones interact with externally generated acoustic components, both limited by a level-dependent auditory filter, to produce an internal excitation envelope that is the basis for discriminating between SAM and QFM waveforms. It is al so suggested that individual differences at low levels may be due to internal phase ambiguities.
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High-level Psychophysical Tuning Curves: Forward Masking in Normal-hearing and Hearing- impaired Listeners

Nelson, D.A. (1991). Journal of Speech and Hearing Research, 34, 1233-1249.

Forward-masked psychophysical tuning curves (PTCs) were obtained for 1000-Hz probe tones at multiple probe levels from one ear of 26 normal-hearing listeners and from 24 ears of 21 hearing-impaired listeners with cochlear hearing loss. Comparisons betwe en normal-hearing and hearing-impaired PTCs were made at equivalent masker levels near the tips of PTCs. Comparisons were also made of PTC characteristics obtained by fitting each PTC with three straight-line segments using least-squares fitting procedur es. Abnormal frequency resolution was only revealed as abnormal downward spread of masking. The low-frequency slopes of PTCs from hearing-impaired listeners were not different from those of normal-hearing listeners, that is, hearing-impaired listeners d id not demonstrate abnormal upward spread of masking when equivalent masker levels were compared. Ten hearing-impaired ears demonstrated abnormally broad PTCs, due exclusively to reduced high-frequency slopes in their PTCs. This abnormal downward spread of masking was only observed in listeners with hearing losses greater than 40 dB HL. From these results, it would appear that some, but not all, cochlear hearing losses greater than 40 dB HL influence the sharp tuning capabilities usually associated wit h outer hair cell function.
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An analysis of psychophysical tuning curves in normal and pathological ears

Carney, A.E. and Nelson, D.A. (1983). J. Acoust. Soc. Amer., 73, 268-278.

Simultaneous psychophysical tuning curves were obtained from normal-hearing and hearing-impaired listeners, using probe tones that were either at similar sound pressure levels or at similar sensation levels for the two types of listeners. Tuning curves from the hearing-impaired listeners were flat, erratic, broad, and/or inverted, depending upon the frequency region of the probe tone and the frequency characteristics of the hearing loss. Tuning curves from the normal-hearing listeners at l ow-SPL's were sharp as expected; tuning curves at high-SPL's were discontinuous. An analysis of high-SPL tuning curves suggests that tuning curves from normal-hearing listeners reflect low-pass filter characteristics instead of the sharp bandpass filter c haracteristics seen with low-SPL probe tones. Tuning curves from hearing-impaired listeners at high-SPL probe levels appear to reflect similar low-pass filter characteristics, but with much more gradual high-frequency slopes than in the normal ear. This a ppeared as abnormal downward spread of masking. Relatively good temporal resolution and broader tuning mechanisms were proposed to explain inverted tuning curves in the hearing-impaired listeners.

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Updated: 23 September 2008  by Lab Personnel, Clinical Psychoacoustics Laboratory  (University of Minnesota)
URL: http://www.cpl.umn.edu/auditory.htm   (Clinical Psychoacoustics Laboratory)