Impaired Ears Research Articles

Modeling auditory-nerve responses for high sound pressure levels in the normal and impaired auditory periphery

This paper presents a computational model to simulate normal and impaired auditory-nerve (AN) fiber responses in cats. The model responses match physiological data over a wider dynamic range than previous auditory models. This is achieved by providing two modes of basilar membrane excitation to the inner hair cell (IHC) rather than one. The two modes are generated by two parallel filters, component 1 (C1) and component 2 (C2), and the outputs are subsequently transduced by two separate functions. The responses are then added and passed through the IHC low-pass filter followed by the IHC-AN synapse model and discharge generator. The C1 filter is a narrow-band, chirp filter with the gain and bandwidth controlled by a nonlinear feed-forward control path. This filter is responsible for low and moderate level responses. A linear, static, and broadly tuned C2 filter followed by a nonlinear, inverted and nonrectifying C2 transduction function is critical for producing transition region and high-level effects. Consistent with Kiang's two-factor cancellation hypothesis, the interaction between the two paths produces effects such as the C1/C2 transition and peak splitting in the period histogram. The model responses are consistent with a wide range of physiological data from both normal and impaired ears for stimuli presented at levels spanning the dynamic range of hearing.

Volterra Slice otoacoustic emissions recorded using maximum length sequences from patients with sensorineural hearing loss

When normally hearing ears are stimulated with maximum length sequences (MLS) of clicks, a family of non-linear temporal interaction components of otoacoustic emissions (OAEs) can be derived, which have been named Volterra Slice OAEs (VS OAEs). This study investigates the sensitivity of VS OAEs to sensorineural hearing impairment in adults, compared to that of the widely used derived non-linear click evoked OAE (DNL CEOAE). VS OAEs and DNL CEOAEs were obtained from 24 normally hearing and 24 hearing impaired ears using a custom-built MLS system and a Otodynamics ‘ILO88’ OAE Analyzer, respectively. The results show that, based on waveform reproducibility, VS OAEs are as successful as DNL CEOAEs at separating normal from impaired ears at the audiometric frequencies of 1 and 2 kHz, where a strong correlation is found between the amplitudes of the two OAE types. At 4 kHz however, VS OAEs are a significantly better indicator of hearing loss than DNL CEOAEs. This difference at 4 kHz appears to be due to the lack of stimulus artefact contamination of VS OAEs in the early, high frequency portion of the response. The findings suggest that VS OAEs may provide a better diagnostic and monitoring tool for hearing loss at high frequencies than the conventional DNL CEOAE.

Correction of the Peripheral Spatiotemporal Response Pattern: A Potential New Signal-Processing Strategy

The purpose of this paper is to introduce a new signal-processing strategy, spatiotemporal pattern correction (SPC), that is based on our knowledge of the level-dependent temporal response properties of auditory nerve fibers in normal and impaired ears. In normal-hearing listeners, tuning is sharp for low-level inputs and broadens as input level increases. When peripheral filters change their shape with input level, the phase properties of the filters and the latency of the filter's response also change. However, in listeners with hearing loss, tuning is broad for both low- and high-level inputs. Thus, there is little change in the phase properties of the filters for different input levels. The SPC strategy manipulates the temporal aspects of different frequency channels of sounds in an attempt to "correct" for this abnormal spatiotemporal response pattern of the impaired ear. Quality judgments and intelligibility measures of speech processed at various SPC strengths were obtained from a small group of normal-hearing listeners and listeners with hearing loss. In general, listeners with hearing loss preferred sentences with some degree of SPC processing, whereas normal-hearing listeners preferred unprocessed sentences. Benefit from SPC on the nonsense syllable test varied greatly across phonemes and listeners. A more comprehensive study of listeners with different degrees and configurations of hearing loss is needed to determine the amount of SPC benefit.

State of the States 2006

State of the States 2006

Bilateral or unilateral amplification: Is there a difference? A brief tutorial

“… the basic question for the clinician faced with providing benefit to the aurally impaired individual is not whether two ears are better than one, but rather, ‘Are two hearing impaired ears coupl...

Audiometric predictions using stimulus-frequency otoacoustic emissions and middle ear measurements.

The goals of the study are to determine how well stimulus-frequency otoacoustic emissions (SFOAEs) identify hearing loss, classify hearing loss as mild or moderate-severe, and correlate with pure-tone thresholds in a population of adults with normal middle ear function. Other goals are to determine if middle ear function as assessed by wideband acoustic transfer function (ATF) measurements in the ear canal account for the variability in normal thresholds, and if the inclusion of ATFs improves the ability of SFOAEs to identify hearing loss and predict pure-tone thresholds. The total suppressed SFOAE signal and its corresponding noise were recorded in 85 ears (22 normal ears and 63 ears with sensorineural hearing loss) at octave frequencies from 0.5 to 8 kHz, using a nonlinear residual method. SFOAEs were recorded a second time in three impaired ears to assess repeatability. Ambient-pressure ATFs were obtained in all but one of these 85 ears and were also obtained from an additional 31 normal-hearing subjects in whom SFOAE data were not obtained. Pure-tone air and bone conduction thresholds and 226-Hz tympanograms were obtained on all subjects. Normal tympanometry and the absence of air-bone gaps were used to screen subjects for normal middle ear function. Clinical decision theory was used to assess the performance of SFOAE and ATF predictors in classifying ears as normal or impaired, and linear regression analysis was used to test the ability of SFOAE and ATF variables to predict the air conduction audiogram. The ability of SFOAEs to classify ears as normal or hearing impaired was significant at all test frequencies. The ability of SFOAEs to classify impaired ears as either mild or moderate-severe was significant at test frequencies from 0.5 to 4 kHz. SFOAEs were present in cases of severe hearing loss. SFOAEs were also significantly correlated with air conduction thresholds from 0.5 to 8 kHz. The best performance occurred with the use of the SFOAE signal-to-noise ratio as the predictor, and the overall best performance was at 2 kHz. The SFOAE signal-to-noise measures were repeatable to within 3.5 dB in impaired ears. The ATF measures explained up to 25% of the variance in the normal audiogram; however, ATF measures did not improve SFOAEs predictors of hearing loss except at 4 kHz. In common with other OAE types, SFOAEs are capable of identifying the presence of hearing loss. In particular, SFOAEs performed better than distortion-product and click-evoked OAEs in predicting auditory status at 0.5 kHz; SFOAE performance was similar to that of other OAE types at higher frequencies except for a slight performance reduction at 4 kHz. Because SFOAEs were detected in ears with mild to severe cases of hearing loss, they may also provide an estimate of the classification of hearing loss. Although SFOAEs were significantly correlated with hearing threshold, they do not appear to have clinical utility in predicting a specific behavioral threshold. Information on middle ear status as assessed by ATF measures offered minimal improvement in SFOAE predictions of auditory status in a population of normal and impaired ears with normal middle ear function. However, ATF variables did explain a significant fraction of the variability in the audiograms of normal ears, suggesting that audiometric thresholds in normal ears are partially constrained by middle ear function as assessed by ATF tests.

Nonsurgical Home Treatment of Middle Ear Effusion and Associated Hearing loss in Children. Part II: Validation Study

In this prospective follow-up investigation, we examined the efficacy of a modified Politzer device in the home treatment of persistent middle ear effusion (MEE) and associated hearing loss in children who had previously participated in a similar clinical trial. Our study group was made up of 38 patients who had been either (1) untreated control participants in the previous study whose hearing in one or both ears had not returned to normal within 11 weeks of their initial audiologic pretest ("former control group"; n = 30), or (2) active-treatment participants in the previous study whose hearing sensitivity in at least one ear had not improved to within normal limits after treatment and who elected to undergo a continuation of treatment ("extended-treatment group"; n = 8). Treatment efficacy was determined by comparing differences in pre- and posttreatment air-conduction thresholds and otoscopic findings. Following treatment, the former control group experienced significant improvements in hearing sensitivity at all frequencies; at the posttreatment test, hearing sensitivity was within normal limits in 43 of 60 ears (71.7%), and normal or moderate tympanic membrane mobility was observed in 30 of 34 otoscopically examined ears (88.2%). In the extended-treatment group, hearing sensitivity returned to within normal limits in 9 of 10 impaired ears (90.0%). These findings further substantiate the efficacy of our modified Politzer device in improving middle ear function and hearing sensitivity in children with MEE, and they support the reliability of the findings reported in our previous study. These results also indicate that many patients in whom initial treatment is not successful may benefit from extended treatment.

Otoacoustic emission latency, cochlear tuning, and hearing functionality in neonates

Transient evoked otoacoustic emissions of a large population of neonates (466 ears) are analyzed, with the aim of establishing if a significant latency difference can be observed between "pass" (333) and "fail" (133) ears, discriminated with a screening protocol based on band and global reproducibility. The ears that did not pass the test in at least one frequency band are named "fail," for simplicity, but they should be more appropriately defined as "partial pass." In a previous study, significantly different average latencies had been observed in adult subjects, comparing normal hearing and hearing impaired ears [J. Acoust. Soc. Am. 111, 297-308 (2002)], but no similar study has been conducted on neonates yet. An improved wavelet technique was applied to transient evoked otoacoustic emission data, to get accurate experimental measurements of the otoacoustic emission latency. The results show statistically significant differences between the latency distributions of the "pass" and "fail" populations, with the "fail" latencies longer. However, non-Gaussianity of the distributions and systematic errors associated with low reproducibility levels suggested using a conservative approach in the data analysis and interpretation. New otoacoustic estimates of cochlear tuning in neonates are also provided.

Perception of Spectral Contrast by Hearing-Impaired Listeners

The ability to discriminate the spectral shapes of complex sounds is critical to accurate speech perception. Part of the difficulty experienced by listeners with hearing loss in understanding speech sounds in noise may be related to a smearing of the internal representation of the spectral peaks and valleys because of the loss of sensitivity and an accompanying reduction in frequency resolution. This study examined the discrimination by hearing-impaired listeners of highly similar harmonic complexes with a single spectral peak located in 1 of 3 frequency regions. The minimum level difference between peak and background harmonics required to discriminate a small change in the spectral center of the peak was measured for peaks located near 2, 3, or 4 kHz. Component phases were selected according to an algorithm thought to produce either highly modulated (positive Schroeder) or very flat (negative Schroeder) internal waveform envelopes in the cochlea. The mean amplitude difference between a spectral peak and the background components required for discrimination of pairs of harmonic complexes (spectral contrast threshold) was from 4 to 19 dB greater for listeners with hearing impairment than for a control group of listeners with normal hearing. In normal-hearing listeners, improvements in threshold were seen with increasing stimulus level, and there was a strong effect of stimulus phase, as the positive Schroeder stimuli always produced lower thresholds than the negative Schroeder stimuli. The listeners with hearing loss showed no consistent spectral contrast effects due to stimulus phase and also showed little improvement with increasing stimulus level, once their sensitivity loss was overcome. The lack of phase and level effects may be a result of the more linear processing occurring in impaired ears, producing poorer-than-normal frequency resolution, a loss of gain for low amplitudes, and an altered cochlear phase characteristic in regions of damage.

Transient-evoked stimulus-frequency and distortion-product otoacoustic emissions in normal and impaired ears

Transient-evoked stimulus-frequency otoacoustic emissions (SFOAEs), recorded using a nonlinear differential technique, and distortion-product otoacoustic emissions (DPOAEs) were measured in 17 normal-hearing and 10 hearing-impaired subjects using pairs of tone pips (pp), gated tones (gg), and for DPOAEs, continuous and gated tones (cg). Temporal envelopes of stimulus and OAE waveforms were obtained by narrow-band filtering at the stimulus or DP frequency. Mean SFOAE latencies in normal ears at 2.7 and 4.0 kHz decreased with increasing stimulus level and were larger at 4.0 kHz than latencies in impaired ears. Equivalent auditory filter bandwidths were calculated as a function of stimulus level from SFOAE latencies by assuming that cochlear transmission is minimum phase. DPOAE latencies varied less with level than SFOAE latencies. The ppDPOAEs often had two (or more) peaks separated in time with latencies consistent with model predictions for distortion and reflection components. Changes in ppDPOAE latency with level were sometimes explained by a shift in relative amplitudes of distortion and reflection components. The pp SFOAE SPL within the main spectral lobe of the pip stimulus was higher for normal ears in the higher-frequency half of the pip than the lower-frequency half, which is likely an effect of basilar membrane two-tone suppression.

Dead regions and pitch perception

The perception of pitch for pure tones with frequencies falling inside low- or high-frequency dead regions (DRs) was examined. Subjects adjusted a variable-frequency tone to match the pitch of a fixed tone. Matches within one ear were often erratic for tones falling in a DR, indicating unclear pitch percepts. Matches across ears of subjects with asymmetric hearing loss, and octave matches within ears, indicated that tones falling within a DR were perceived with an unclear pitch and/or a pitch different from "normal" whenever the tones fell more than 0.5 octave within a low- or high-frequency DR. One unilaterally impaired subject, with only a small surviving region between 3 and 4 kHz, matched a fixed 0.5-kHz tone in his impaired ear with, on average, a 3.75-kHz tone in his better ear. When asked to match the 0.5-kHz tone with an amplitude-modulated tone, he adjusted the carrier and modulation frequencies to about 3.8 and 0.5 kHz, respectively, suggesting that some temporal information was still available. Overall, the results indicate that the pitch of low-frequency tones is not conveyed solely by a temporal code. Possibly, there needs to be a correspondence between place and temporal information for a normal pitch to be perceived.

Speech recognition abilities in noise for children with severe-to-profound unilateral hearing impairment

The purpose of this research was to compare the signal-to-noise ratio required for equal performance for children (aged 6-14 years) with normal hearing (N=17) versus those with severe-to-profound unilateral hearing impairment (N=20) who can be at a disadvantage, particularly when sounds are presented to the impaired ear. The listening environment is designed to approximate that which is encountered in a typical classroom. All signals (Hearing in Noise Test-Children and Nonsense Syllable Test) were presented in the sound field from various azimuths with continuous noise presented from all quadrants. The children were required to repeat twenty items, from each test, in each listening condition. The intensity of the presentations was varied based on the accuracy of previous items. Average signal-to-noise ratios are compared between and within groups. (1) In most listening conditions, significantly greater signal-to-noise ratios were needed by those with unilateral hearing impairment than those with normal hearing, on both speech tests. (2) In every listening condition, both groups required significantly greater signal-to-noise ratios to perform equally well on the Nonsense Syllable Test as on the Hearing-In-Noise Test-Children. (3) For the Hearing-In-Noise Test-Children, children with normal hearing required significantly greater signal-to-noise ratios when facing the signal than when the signal was presented to a normally hearing ear (monaural direct). (4) On both tests, the children with unilateral hearing impairment required significantly greater signal-to-noise ratios when facing the signal than in the monaural direct condition. (5) On both tests, the children with unilateral hearing impairment required significantly greater signal-to-noise ratios when the signal was presented to the impaired ear (monaural indirect) than when facing the signal. (1) The children with unilateral hearing impairment require a more advantageous listening condition to perform equally as well as their normally hearing counterparts. (2) All of the children benefited from signals delivered in a monaural direct condition. (3) The children with unilateral hearing impairment performed best in the monaural direct condition or when facing the signal at zero degrees. (4) Significantly greater signal-to-noise ratios were needed for both groups when restricted contextual cues were available versus when sentential cues were available.

« Audio 4 » : un test vocal simple et rapide pour le dépistage des surdités moyennes des enfants à l’âge de quatre ans

The need for repeated auditory screening throughout early childhood faces the obstacle of the lack of objective validated material. Objectives. – The goal of this two-year prospective study was to create and validate frequency-based word/picture lists appropriate for four-year-olds. Words were chosen not on the basis of the acoustic frequency of phoneme production, but on frequencies corresponding to their optimal recognition. Responses thus were to predict pure-tone threshold curves. Material and methods. – First of all, the linguistics laboratory created lists. Next, we proceeded to validate the form of the test: this involved verifying that the words selected on the basis of their frequency characteristics were common and well-known to children of this age. During the first year of the study, the picture boards were tested in a hospital otolaryngology service (66 children) and in a public health service (500 children) and corrected. Results. – All of the words and pictures were known during the next year by 5088 children. The second step was the audiometric validation of the test in a paediatric otolaryngology service. We compared classification of normal and impaired ears according to tonal audiograms and according to “Audio 4”: 360 children were tested. Results were the following ones: Se: 0.81, Sp: 0.96, PPV: 0.91, NPV: 0.93. “Audio 4” therefore allows for prediction of pure-tone curves. Conclusion. – This gives us hope that, directly interpretable by physicians, Audio 4, a rapid test which is attractive to children, will be used in diagnostic paediatric examinations whenever necessary.

Transient evoked otoacoustic emissions recorded using maximum length sequences from patients with sensorineural hearing loss

Much research has shown that transient evoked otoacoustic emissions (TEOAEs) can successfully separate normally hearing and hearing impaired populations. However, this finding comes from TEOAEs recorded using conventional averaging at low stimulation rates. Presenting clicks according to maximum length sequences (MLSs) enables TEOAEs to be recorded at very high stimulation rates. This study compares conventional and MLS TEOAEs in normally hearing and hearing impaired adults. Stimulus presentation rates of 40 clicks/s (conventional) and 5000 clicks/s (MLS) were used. The ‘linear’ TEOAEs (i.e., the directly recorded waveforms), the ‘level nonlinear’ (LNL) TEOAEs (i.e., those derived from two linear waveforms separated by a known difference in stimulus level) and the ‘rate nonlinear’ (RNL) TEOAEs (i.e., obtained by subtracting the emission recorded at 5000 clicks/s from that at 40 clicks/s at a fixed stimulus level) were examined to compare how they separated the normally hearing and hearing impaired subjects. When compared to the results for both conventional and MLS linear or LNL TEOAEs, the present study found that the RNL results best reflected the patients’ hearing loss, although the conventional linear and LNL responses performed nearly as well. Only two impaired ears (2%), both with a best threshold of 30 dB HL at 1000 Hz, produced RNL responses with amplitude within the range produced by 95% of the normal group.

Modeling the growth rate of distortion product otoacoustic emissions by active nonlinear oscillators.

In this work, growth-rate curves of the 2 f1-f2 distortion product otoacoustic emission (DPOAE) are analyzed in a population of 30 noise exposed subjects, including both normal-hearing and hearing impaired subjects. A particular embedded limit-cycle oscillator equation is used to model the cochlear resonant response at the cochlear places of the primary and secondary tone frequencies (f2 and 2 f1-f2). The parameters of the oscillator equation can be directly interpreted in terms of effectiveness of the cochlear feedback mechanisms associated with the active filter amplification. A two-sources paradigm is included in the model, in agreement with experimental evidence and with the assumptions of more detailed full cochlear models based on the transmission line formalism. According to this paradigm, DPOAEs are nonlinearly generated at the cochlear place that is resonant at frequency f2, and coherently reflected at the 2 f1-f2 place. The analysis shows that the model, which had been previously used to describe the relaxation dynamics of transient evoked otoacoustic emissions (TEOAEs), also correctly predicts the observed growth rate of the DPOAE response as a function of the primary tones amplitude. A significant difference is observed between normal and impaired ears. The comparison between the growth rate curves at different frequencies provides information about the dependence of cochlear tuning on frequency.

Physiological assessment of contrast-enhancing frequency shaping and multiband compression in hearing aids

Spectral enhancement is now being used in many hearing aids in an attempt to compensate for broadened cochlear filtering. However, spectral enhancement may be counteracted by multiband-compression algorithms designed to compensate for the reduced dynamic range of the impaired cochlea. An alternative scheme for spectral enhancement, contrast-enhancing frequency shaping (CEFS), has been proposed, which results in an improved neural representation of the first and second formants of voiced speech segments in the impaired ear. In this paper, models of the normal and impaired ear are used to assess the compatibility of CEFS with multiband compression. Model auditory nerve responses were assessed under four conditions: (1) unmodified speech presented to a normal ear; (2) amplified, unshaped speech presented to an impaired ear; (3) CEFS speech presented to an impaired ear; and (4) CEFS+multiband-compression speech presented to an impaired ear. The results show that multiband compression does not reduce the benefits of CEFS, and in some cases multiband compression assists in preventing distortion of the neural representation of formants. These results indicate that the combination of contrast-enhancing frequency shaping and multiband compression should lead to improved perception of voiced speech segments in hearing aid users.

Behavioral estimates of compression in normal and impaired ears

Over the last 7 years, forward masking techniques have been used to estimate peripheral compression in the human auditory system. The growth of masking and temporal masking curve (TMC) techniques estimate the response to a tone at characteristic frequency (CF) by comparing the masking function (masker level as a function of signal level and masker-signal interval, respectively) for a masker at the signal frequency with the masking function for a masker below the signal frequency (assumed to be processed linearly at high CFs). Compression can also be estimated using the additivity of forward masking technique, in which the effects on signal threshold of combining two equally effective maskers are used to derive the exponent. Overall, the results suggest strong compression in humans (exponent of 0.2) across the range of CFs tested so far (250 to 8000 Hz). The behavioral techniques also suggest that a sensorineural hearing loss of greater than about 50 dB results in an almost complete linearization of the response. However, recent TMC data suggest that less severe hearing losses are associated with a reduction in gain, and a reduction in the level range over which compression is present, but no reduction in the maximum compression.

Cochlear nonlinearity between 500 and 8000 Hz in listeners with moderate cochlear hearing loss

For two listeners with flat hearing loss, temporal masking curves (TMCs) were measured for probe frequencies (Fp) of 0.5, 1.0, 2.0, 4.0, and 8.0 kHz and masker frequencies of 0.5, 0.6, 0.7, 0.9, 1.0, 1.05, 1.1, and 1.2 Fp. From these, basilar membrane (BM) input/output (IO) functions and psychophysical tuning curves (PTCs) were derived and compared with corresponding data for normal-hearing listeners. Linear IO functions were observed for one ear only and for probe frequencies of 4 kHz and above. This result is consistent with the consequences of severe outer hair cell (OHC) damage on the BM response. Elsewhere, however, IO functions showed residual compression, with slopes in the compression region close to normal. This suggests that either the impairment relates mostly to inner hair cell (IHC) dysfunction, or that OHC dysfunction reduces the gain of the BM at low levels while maintaining the degree of maximum compression. The data suggest that the active and the passive BM mechanisms have different relative positions (in frequency) in the apical and the basal regions of the cochlea. Across probe frequencies, the slopes of the TMCs for off-frequency maskers are shallower for the impaired ears. It is considered that this possibly reflects IHC-related compression.

Cochlear nonlinearity between 500 and 8000 Hz in listeners with impaired hearing

Cochlear nonlinearity was estimated in listeners with impaired hearing using a forward-masking method. For a fixed low-level probe, the masker level required to mask the probe was measured as a function of the masker-probe interval, to produce a temporal masking curve (TMC). TMCs were measured for probe frequencies from 500 to 8000 Hz, and for masker frequencies from 0.5 to 1.6 times the probe frequency. Unlike what happens for normal-hearing (NH) listeners [Lopez-Poveda et al., J. Acoust. Soc. Am. 113, 951–960 (2003)], TMCs for on-frequency maskers sometimes show a single slope, suggesting linear responses for tones at CF. Sometimes, however, two distinct slopes are visible, suggesting remaining compression. Both patterns are uncorrelated with the absolute threshold and are consistent with selective damage to outer or inner hair cells (IHC), respectively. Remarkably, the slope of the TMCs for very low-frequency maskers is shallower for the impaired ears than for normal ones. This result implies that for NH listeners, the slope of the TMCs for very low-frequency maskers reflects some kind of compression, even at high CFs. It is discussed that this compression is likely to occur at the IHC rather than at the basilar membrane. [Work supported by FIS PI020343, G03/203, and Oticon Spain.]

Distortion product otoacoustic emission suppression tuning curves in normal-hearing and hearing-impaired human ears

Distortion product otoacoustic emission (DPOAE) suppression measurements were made in 20 subjects with normal hearing and 21 subjects with mild-to-moderate hearing loss. The probe consisted of two primary tones (f2, f1), with f2 held constant at 4 kHz and f2/f1 = 1.22. Primary levels (L1, L2) were set according to the equation L1 = 0.4 L2 + 39 dB [Kummer et al., J. Acoust. Soc. Am. 103, 3431-3444 (1998)], with L2 ranging from 20 to 70 dB SPL (normal-hearing subjects) and 50-70 dB SPL (subjects with hearing loss). Responses elicited by the probe were suppressed by a third tone (f3), varying in frequency from 1 octave below to 1/2 octave above f2. Suppressor level (L3) varied from 5 to 85 dB SPL. Responses in the presence of the suppressor were subtracted from the unsuppressed condition in order to convert the data into decrements (amount of suppression). The slopes of the decrement versus L3 functions were less steep for lower frequency suppressors and more steep for higher frequency suppressors in impaired ears. Suppression tuning curves, constructed by selecting the L3 that resulted in 3 dB of suppression as a function of f3, resulted in tuning curves that were similar in appearance for normal and impaired ears. Although variable, Q10 and Q(ERB) were slightly larger in impaired ears regardless of whether the comparisons were made at equivalent SPL or equivalent sensation levels (SL). Larger tip-to-tail differences were observed in ears with normal hearing when compared at either the same SPL or the same SL, with a much larger effect at similar SL. These results are consistent with the view that subjects with normal hearing and mild-to-moderate hearing loss have similar tuning around a frequency for which the hearing loss exists, but reduced cochlear-amplifier gain.