Comparison of three procedures for initial fitting of compression hearing aids. III. Inexperienced versus experienced users

Clinical Trials and Outcome Measures in Adults With Hearing Loss

Clinical trials are designed to evaluate interventions that prevent, diagnose or treat a health condition and provide the evidence base for improving practice in health care. Many health professionals, including those working within or allied to hearing health, are expected to conduct or contribute to clinical trials. Recent systematic reviews of clinical trials reveal a dearth of high quality evidence in almost all areas of hearing health practice. By providing an overview of important steps and considerations concerning the design, analysis and conduct of trials, this article aims to give guidance to hearing health professionals about the key elements that define the quality of a trial. The article starts out by situating clinical trials within the greater scope of clinical evidence, then discusses the elements of a PICO-style research question. Subsequently, various methodological considerations are discussed including design, randomization, blinding, and outcome measures. Because the literature on outcome measures within hearing health is as confusing as it is voluminous, particular focus is given to discussing how hearing-related outcome measures affect clinical trials. This focus encompasses how the choice of measurement instrument(s) affects interpretation, how the accuracy of a measure can be estimated, how this affects the interpretation of results, and if differences are statistically, perceptually and/or clinically meaningful to the target population, people with hearing loss.

Listener Factors Explain Little Variability in Self-Adjusted Hearing Aid Gain

Self-adjustment of hearing aid gain can provide valuable information about the gain preferences of individual listeners, but these preferences are not well understood. Listeners with mild-to-moderate hearing loss used self-adjustment to select amplification gain and compression parameters in real time on a portable touch screen device while listening in quiet and noisy backgrounds. Adjustments to gain prescribed by the National Acoustics Laboratories' non-linear fitting procedure (NAL-NL2) showed large between-subject variability. Known listener characteristics (age, gender, hearing thresholds, hearing aid experience, acceptable noise level, and external ear characteristics) and listener engagement with the self-adjustment software were examined as potential predictors of this variability. Neither listener characteristics nor time spent adjusting gain were robust predictors of gain change from NAL-NL2. Listeners with less than 2 years of hearing aid experience and who also had better hearing thresholds tended to select less gain, relative to NAL-NL2, than experienced hearing aid users who had poorer thresholds. Listener factors explained no more than 10% of the between-subject variance in deviation from NAL-NL2, suggesting that modifying prescriptive fitting formulae based on the factors examined here would be unlikely to result in amplification parameters that are similar to user-customized settings. Self-adjustment typically took less than 3 min, indicating that listeners could use comparable technology without a substantial time commitment.

Speech perception, real-ear measurements and self-perceived hearing impairment after remote and face-to-face programming of hearing aids: A randomized single-blind agreement study

INTRODUCTION

Current literature does not provide strong evidence that remote programming of hearing aids is effective, despite its increasing use by audiologists. We tested speech perception outcomes, real-ear insertion gain, and changes in self-perceived hearing impairment after face-to-face and remote programming of hearing aids in a randomized multicentre, single-blind crossover study.

METHODS

Adult experienced hearing aid users were enrolled during routine follow-up visits to audiology clinics. Hearing aids were programmed both face to face and remotely, then participants randomly received either the face-to-face or remote settings in a blinded manner and were evaluated 5 weeks later. Participants then received the other settings and were evaluated 5 weeks later.

RESULTS

Data from 52 out of 60 participants were analysed. We found excellent concordance in performance of hearing aids programmed face to face and remotely for speech understanding in quiet (phonetically balanced kindergarten test - intraclass correlation coefficient of 0.92 (95% confidence interval: 0.87-0.95)), and good concordance in performance for speech understanding in noise (phonetically balanced kindergarten +5 dB signal-to-noise ratio - intraclass correlation coefficient of 0.71 (95% confidence interval: 0.55-0.82)). Face-to-face and remote programming took 10 minutes (±2.9) and 10 minutes (±2.8), respectively. Real-ear insertion gains were highly correlated for input sound at 50, 65 and 80 dB sound pressure levels. The programming type did not affect the abbreviated profile of hearing aid questionnaire scores.

CONCLUSIONS

In experienced hearing aid users, face-to-face and remote programming of hearing aids give similar results in terms of speech perception, with no increase in the time spent on patients' care and no difference in self-reported hearing benefit.

CLINICALTRIALS.GOV IDENTIFIER

NCT02589561.

Perceptual Effects of Adjusting Hearing-Aid Gain by Means of a Machine-Learning Approach Based on Individual User Preference

This study investigated a method to adjust hearing-aid gain by use of a machine-learning algorithm that estimates the optimal setting of gain parameters based on user preference indicated in an iterative paired-comparison procedure. Twenty hearing-impaired participants completed this procedure for 12 different sound scenarios. During the adjustment procedure, their task was to indicate a preference based on one of three sound attributes: Basic Audio Quality, Listening Comfort, or Speech Clarity. In a double-blind comparison of recordings of the processed scenarios, and using the same attributes as criteria, the adjusted gain settings were subsequently compared with two prescribed settings of the same hearing aid (with and without activation of an automatic sound-classification system). The results showed that the adjustment method provided a general improvement of Basic Audio Quality, an improvement of Listening Comfort in a traffic-noise scenario but not in three scenarios with speech babble, and no significant improvement of Speech Clarity. A large variation in gain adjustments was observed across participants, both among those who did benefit and among those who did not benefit from the adjustment. There was no clear connection between the gain adjustments and the perceived benefit, which indicates that the preferred gain settings for a given sound scenario and a given listening intention are highly individual and difficult to predict.

Effects of Amplification and Hearing Aid Experience on the Contribution of Specific Frequency Bands to Loudness

OBJECTIVES

The primary aim of this study is to describe the effect of hearing aid amplification on the contribution of specific frequency bands to overall loudness in adult listeners with sensorineural hearing loss (SNHL). Results for listeners with SNHL were compared with results for listeners with normal hearing (NH) to evaluate whether amplification restores the normal perception of loudness for broadband sound. A secondary aim of this study is to determine whether the loudness perception of new hearing aid users becomes closer to normal over the first few months of hearing aid use. It was hypothesized that amplification would cause the high-frequency bands to contribute most to the perception of loudness and that this effect might decrease as new hearing aid users adapt to amplification.

DESIGN

In experiment 1, 8 adult listeners with SNHL completed a two-interval forced-choice loudness task in unaided and aided conditions. A control group of 7 listeners with NH completed the task in the unaided condition only. Stimuli were composed of seven summed noise bands whose levels were independently adjusted between presentations. During a trial, two stimuli were presented, and listeners determined the louder one. The correlation between the difference in levels for a given noise band on every trial and the listener's response was calculated. The resulting measure is termed the perceptual weight because it provides an estimate of the relative contribution of a given frequency region to overall loudness. In experiment 2, a separate group of 6 new hearing aid users repeated identical procedures on 2 sessions separated by 12 weeks.

RESULTS

Results for listeners with SNHL were similar in experiments 1 and 2. In the unaided condition, perceptual weights were greatest for the low-frequency bands. In the aided condition, perceptual weights were greatest for the high-frequency bands. On average, the aided perceptual weights for listeners with SNHL for high-frequency bands were greater than the unaided weights for listeners with NH. In experiment 2, hearing aid experience did not have a significant effect on perceptual weights.

CONCLUSIONS

The high frequencies seem to dominate loudness perception in listeners with SNHL using hearing aids as they do in listeners with NH. However, the results suggest that amplification causes high frequencies to have a larger contribution to overall loudness compared with listeners with NH. The contribution of the high frequencies to loudness did not change after an acclimatization period for the first-time hearing aid users.

Self-Adjusted Amplification Parameters Produce Large Between-Subject Variability and Preserve Speech Intelligibility

The current study used the self-fitting algorithm to allow listeners to self-adjust hearing-aid gain or compression parameters to select gain for speech understanding in a variety of quiet and noise conditions. Thirty listeners with mild to moderate sensorineural hearing loss adjusted gain parameters in quiet and in several types of noise. Outcomes from self-adjusted gain and audiologist-fit gain indicated consistent within-subject performance but a great deal of between-subject variability. Gain selection did not strongly affect intelligibility within the range of signal-to-noise ratios tested. Implications from the findings are that individual listeners have consistent preferences for gain and may prefer gain configurations that differ greatly from National Acoustic Laboratories-based prescriptions in quiet and in noise.

Discrimination of Gain Increments in Speech-Shaped Noises

Frequency-dependent gain adjustments are routine in hearing-aid fittings, whether in matching to real-ear targets or fine-tuning to patient feedback. Patient feedback may be unreliable and fittings inefficient if adjustments are not discriminable. To examine what gain adjustments are discriminable, we measured the just-noticeable differences (JNDs) for level increments in speech-shaped noises processed with prescription gains. JNDs were measured in the better ears of 38 participants with hearing impairment using a fixed-level, same-different task. JNDs were measured for increments at six individual frequency-bands: a 0.25-kHz low-pass band; octave-wide bands at 0.5, 1, 2, and 4 kHz; and a 6-kHz high-pass band. JNDs for broadband increments were also measured. JNDs were estimated at d' of 1 for a minimally discriminable increment in optimal laboratory conditions. The JND for frequency-band increments was 2.8 dB excluding the 0.25-kHz low-pass band, for which the JND was 4.5 dB. The JND for broadband increments was 1.5 dB. Participants' median frequency-band and broadband JNDs were positively correlated. JNDs were mostly independent of age, pure-tone thresholds, and cognitive score. In consideration of self-fitting adjustments in noisier conditions, JNDs were additionally estimated at a more sensitive d' of 2. These JNDs were 6 dB for bands below 1 kHz, and 5 dB for bands at and above 1 kHz. Overall, the results suggest noticeable fine-tuning adjustments of 3 dB and self-fitting adjustments of 5 dB.

A Comparison of Personal Sound Amplification Products and Hearing Aids in Ecologically Relevant Test Environments

PURPOSE

The aim of this study was to compare the benefit of self-adjusted personal sound amplification products (PSAPs) to audiologist-fitted hearing aids based on speech recognition, listening effort, and sound quality in ecologically relevant test conditions to estimate real-world effectiveness.

METHOD

Twenty-five older adults with bilateral mild-to-moderate hearing loss completed the single-blinded, crossover study. Participants underwent aided testing using 3 PSAPs and a traditional hearing aid, as well as unaided testing. PSAPs were adjusted based on participant preference, whereas the hearing aid was configured using best-practice verification protocols. Audibility provided by the devices was quantified using the Speech Intelligibility Index (American National Standards Institute, 2012). Outcome measures assessing speech recognition, listening effort, and sound quality were administered in ecologically relevant laboratory conditions designed to represent real-world speech listening situations.

RESULTS

All devices significantly improved Speech Intelligibility Index compared to unaided listening, with the hearing aid providing more audibility than all PSAPs. Results further revealed that, in general, the hearing aid improved speech recognition performance and reduced listening effort significantly more than all PSAPs. Few differences in sound quality were observed between devices. All PSAPs improved speech recognition and listening effort compared to unaided testing.

CONCLUSIONS

Hearing aids fitted using best-practice verification protocols were capable of providing more aided audibility, better speech recognition performance, and lower listening effort compared to the PSAPs tested in the current study. Differences in sound quality between the devices were minimal. However, because all PSAPs tested in the study significantly improved participants' speech recognition performance and reduced listening effort compared to unaided listening, PSAPs could serve as a budget-friendly option for those who cannot afford traditional amplification.

Comparison of the CAM2A and NAL-NL2 hearing-aid fitting methods for participants with a wide range of hearing losses

OBJECTIVE

To compare preferences for sounds processed via a simulated five-channel compression hearing aid fitted using CAM2A and NAL-NL2.

DESIGN

Within a trial, the same segment of sound was presented twice, once with CAM2A settings and once with NAL-NL2 settings, in random order. The participant indicated which one was preferred and by how much. Stimuli included female and male speech in quiet and four types of music. The compression speed was slow or fast and the input sound level was 50, 65, or 80 dB SPL.

STUDY SAMPLE

Sixteen experienced hearing-aid users with a wide range of sensorineural hearing losses.

RESULTS

For both compression speeds, CAM2A was slightly preferred over NAL-NL2 for input levels of 65 and 80 dB, but NAL-NL2 was slightly preferred at 50 dB SPL.

CONCLUSIONS

Preferences for CAM2A relative to NAL-NL2 vary with input level. The results suggest that preferences for CAM2A might be increased by using lower gains for high frequencies and low input levels.

Measurement and modeling of binaural loudness summation for hearing-impaired listeners

The summation of loudness across ears is often studied by measuring the level difference required for equal loudness (LDEL) of monaural and diotic sounds. Typically, the LDEL is ∼5-6 dB, consistent with the idea that a diotic sound is ∼1.5 times as loud as the same sound presented monaurally at the same level, as predicted by the loudness model of Moore and Glasberg [J. Acoust. Soc. Am. 121, 1604-1612 (2007)]. One might expect that the LDEL would be <5-6 dB for hearing-impaired listeners, because loudness recruitment leads to a more rapid change of loudness for a given change in level. However, previous data sometimes showed similar LDEL values for normal-hearing and hearing-impaired listeners. Here, the LDEL was measured for hearing-impaired listeners using narrowband and broadband noises centered at 500 Hz, where audiometric thresholds were near-normal, and at 3000 or 4000 Hz, where audiometric thresholds were elevated. The mean LDEL was 5.6 dB at 500 Hz and 4.2 dB at the higher center frequencies. The results were predicted reasonably well by an extension of the loudness model of Moore and Glasberg.

Effects of bandwidth, compression speed, and gain at high frequencies on preferences for amplified music

This article reviews a series of studies on the factors influencing sound quality preferences, mostly for jazz and classical music stimuli. The data were obtained using ratings of individual stimuli or using the method of paired comparisons. For normal-hearing participants, the highest ratings of sound quality were obtained when the reproduction bandwidth was wide (55 to 16000 Hz) and ripples in the frequency response were small (less than ± 5 dB). For hearing-impaired participants listening via a simulated five-channel compression hearing aid with gains set using the CAM2 fitting method, preferences for upper cutoff frequency varied across participants: Some preferred a 7.5- or 10-kHz upper cutoff frequency over a 5-kHz cutoff frequency, and some showed the opposite preference. Preferences for a higher upper cutoff frequency were associated with a shallow high-frequency slope of the audiogram. A subsequent study comparing the CAM2 and NAL-NL2 fitting methods, with gains slightly reduced for participants who were not experienced hearing aid users, showed a consistent preference for CAM2. Since the two methods differ mainly in the gain applied for frequencies above 4 kHz (CAM2 recommending higher gain than NAL-NL2), these results suggest that extending the upper cutoff frequency is beneficial. A system for reducing "overshoot" effects produced by compression gave small but significant benefits for sound quality of a percussion instrument (xylophone). For a high-input level (80 dB SPL), slow compression was preferred over fast compression.

Evidence on self-fitting hearing aids

The research on self-fitting hearing aids is reviewed using evidence-based principles. The evaluation begins with a definition of the research questions followed by a detailed search of the literature and then a review of the relevant studies. Four features of self-fitting hearing aids are reviewed: in-situ threshold measurement, whether an initial fitting prescribed using standard prescription formulae will approximate user preferences, outcomes with training of hearing aids for preferred responses, and assembly and use of the aids. There is at least good quality evidence suggesting that in-situ thresholds can be reliably obtained, that prescribed initial fittings approximate preferred responses, and that users are able to train the hearing aids and would prefer the trained responses. However, evidence on other outcomes and the ability of users to assemble and use such instruments is limited. Gaps in research with self-fitting hearing aids are identified.

Determination of preferred parameters for multichannel compression using individually fitted simulated hearing AIDS and paired comparisons

OBJECTIVE

To determine preferred parameters of multichannel compression using individually fitted simulated hearing aids and a method of paired comparisons.

DESIGN

Fourteen participants with mild to moderate hearing loss listened via a simulated five-channel compression hearing aid fitted using the CAMEQ2-HF method to pairs of speech sounds (a male talker and a female talker) and musical sounds (a percussion instrument, orchestral classical music, and a jazz trio) presented sequentially and indicated which sound of the pair was preferred and by how much. The sounds in each pair were derived from the same token and differed along a single dimension in the type of processing applied. For the speech sounds, participants judged either pleasantness or clarity; in the latter case, the speech was presented in noise at a 2-dB signal-to-noise ratio. For musical sounds, they judged pleasantness. The parameters explored were time delay of the audio signal relative to the gain control signal (the alignment delay), compression speed (attack and release times), bandwidth (5, 7.5, or 10 kHz), and gain at high frequencies relative to that prescribed by CAMEQ2-HF.

RESULTS

Pleasantness increased with increasing alignment delay only for the percussive musical sound. Clarity was not affected by alignment delay. There was a trend for pleasantness to decrease slightly with increasing bandwidth, but this was significant only for female speech with fast compression. Judged clarity was significantly higher for the 7.5- and 10-kHz bandwidths than for the 5-kHz bandwidth for both slow and fast compression and for both talker genders. Compression speed had little effect on pleasantness for 50- or 65-dB SPL input levels, but slow compression was generally judged as slightly more pleasant than fast compression for an 80-dB SPL input level. Clarity was higher for slow than for fast compression for input levels of 80 and 65 dB SPL but not for a level of 50 dB SPL. Preferences for pleasantness were approximately equal with CAMEQ2-HF gains and with gains slightly reduced at high frequencies and were lower when gains were slightly increased at high frequencies. Speech clarity was not affected by changing the gain at high frequencies.

CONCLUSIONS

Effects of alignment delay were small except for the percussive sound. A wider bandwidth was slightly preferred for speech clarity. Speech clarity was slightly greater with slow compression, especially at high levels. Preferred high-frequency gains were close to or a little below those prescribed by CAMEQ2-HF.

Audiologist-driven versus patient-driven fine tuning of hearing instruments

Two methods of fine tuning the initial settings of hearing aids were compared: An audiologist-driven approach--using real ear measurements and a patient-driven fine-tuning approach--using feedback from real-life situations. The patient-driven fine tuning was conducted by employing the Amplifit(®) II system using audiovideo clips. The audiologist-driven fine tuning was based on the NAL-NL1 prescription rule. Both settings were compared using the same hearing aids in two 6-week trial periods following a randomized blinded cross-over design. After each trial period, the settings were evaluated by insertion-gain measurements. Performance was evaluated by speech tests in quiet, in noise, and in time-reversed speech, presented at 0° and with spatially separated sound sources. Subjective results were evaluated using extensive questionnaires and audiovisual video clips. A total of 73 participants were included. On average, higher gain values were found for the audiologist-driven settings than for the patient-driven settings, especially at 1000 and 2000 Hz. Better objective performance was obtained for the audiologist-driven settings for speech perception in quiet and in time-reversed speech. This was supported by better scores on a number of subjective judgments and in the subjective ratings of video clips. The perception of loud sounds scored higher than when patient-driven, but the overall preference was in favor of the audiologist-driven settings for 67% of the participants.

Comparison of two adaptive procedures for fitting a multi-channel compression hearing aid

We compared two adaptive procedures for fitting a multi-channel compression hearing aid. "Camadapt" uses judgements of the loudness of speech stimuli and the tonal quality of music stimuli. "Eartuner" uses judgements of the loudness and clarity of speech stimuli with differing spectral characteristics. Sixteen new users of hearing aids were fitted unilaterally, using each procedure. The fittings were assigned to Programs 1 and 2 in the aid, in a counter-balanced order. Subjects kept a diary of their experiences with each program in everyday life. Following 2-4 weeks of experience, they filled in the APHAB and other questionnaires and were re-fitted using both procedures. Camadapt generally led to higher low-level gains and lower high-level gains than Eartuner. Gains recommended by the procedures did not change following experience. Eight subjects preferred the Camadapt fitting and eight preferred the Eartuner fitting. Most subjects gave high overall satisfaction ratings for both procedures. Test-retest reliability was better for Eartuner than for Camadapt. Preference for the Camadapt fitting was associated with slightly better speech communication with Camadapt, while preference for the Eartuner fitting was associated with fewer problems with aversion for that procedure.

Preferred overall loudness. I: Sound field presentation in the laboratory

This study questions the basic assumption that prescriptive methods for nonlinear, wide dynamic range compression (WDRC) hearing aids should restore overall loudness to normal. Fifteen normal-hearing listeners and twenty-four hearing-impaired listeners (with mild to moderate hearing loss, twelve with and twelve without hearing aid experience) participated in laboratory tests. The participants first watched and listened to video sequences and rated how loud and how interesting the situations were. For the hearing-impaired participants, gain was applied according to the NAL-NL1 prescription. Despite the fact that the NAL-NL1 prescription led to less than normal overall calculated loudness, according to the loudness model of Moore and Glasberg (1997), the hearing-impaired participants rated loudness higher than the normal-hearing participants. The participants then adjusted a volume control to preferred overall loudness. Both normal-hearing and hearing-impaired participants preferred less than normal overall calculated loudness. The results from the two groups of hearing-impaired listeners did not differ significantly.

Preferred overall loudness. II: Listening through hearing aids in field and laboratory tests

In a laboratory study, we found that normal-hearing and hearing-impaired listeners preferred less than normal overall calculated loudness (according to a loudness model of Moore & Glasberg, 1997). The current study verified those results using a research hearing aid. Fifteen hearing-impaired and eight normal-hearing participants used the hearing aid in the field and adjusted a volume control to give preferred loudness. The hearing aid logged the preferred volume control setting and the calculated loudness at that setting. The hearing-impaired participants preferred, in median, loudness levels of -14 phon re normal for input levels from 50 to 89 dB SPL. The normal-hearing participants preferred close to normal overall loudness. In subsequent laboratory tests, using the same hearing aid, both hearing-impaired and normal-hearing listeners preferred less than normal overall calculated loudness, and larger reductions for higher input levels In summary, the hearing-impaired listeners preferred less than normal overall calculated loudness, whereas the results for the normal-hearing listeners were inconclusive.

Acclimatization in first-time hearing aid users using three different fitting protocols

OBJECTIVE

To study auditory acclimatization and outcome in first time hearing aid users fitted with state of the art hearing aids as a function of different hearing aid fitting protocols.

METHODS

Twenty-eight adult subjects participated in the study. Each subject was assigned to one of three study groups (named audiologist driven, AD; patient driven, PD; set-to-target, STT according to the fitting protocol used) and fitted with digital hearing aids (Bernafon Symbio). Speech recognition scores were measured in aided and unaided conditions over a 6-month period.

RESULTS

Five subjects (three from the PD-group, two from the STT group) decided to withdraw from the study during the 6-month-study period, leaving a total of 23 complete data sets for analysis. Aided speech understanding increased significantly over this time period in all three groups. However, average hearing aid insertion gain changes were small over the same period. There were no statistically significant differences in aided or unaided speech recognition scores between the three groups after 2 weeks or after 6 months. On average, twice as many fine tunings of the hearing aids were requested by the patients in the AD and the STT group than in the PD group and subjects in the AD and STT group used their hearing aids approximately twice as much as subjects in the PD group.

CONCLUSIONS

The substantial increase in speech intelligibility without significant changes of the insertion gain of the hearing aids over a 6-month period in all three groups suggests a significant acclimatization effect. Although the speech recognition with hearing aids did not differ significantly among the three study groups after 6 months, the lower average wearing time and the higher number of withdrawals from the study in the PD group suggest that the patients' needs are not adequately met. In terms of aided speech recognition scores and hearing aid wearing time the STT group and the AD group were very similar. However, comments of the patients and the higher rate of withdrawals in the STT group suggest an over-all advantage for the AD fitting protocol.

Tolerable hearing-aid delays: IV. effects on subjective disturbance during speech production by hearing-impaired subjects

OBJECTIVE

We assessed the effects of time delay in a hearing aid on subjective disturbance and reading rates while the user of the aid was speaking, using hearing-impaired subjects and real-time processing. The time delay was constant across frequency.

DESIGN

A digital signal processor was programmed as a four-channel, fast-acting, wide-dynamic-range compression hearing aid. One of four delays could be selected on the aid to produce a total delay of 13, 21, 30, or 40 msec between microphone and receiver. Twenty-five subjects, mostly with near-symmetric hearing impairment of cochlear origin, were fitted bilaterally with behind-the-ear aids connected to the processor. The aids were programmed with insertion gains prescribed by the CAMEQ loudness equalization procedure for each subject and ear. Subjects were asked to read aloud from scripts: speech production rates were measured and subjective ratings of the disturbance of the delay were obtained. Subjects required some training to recognize the effects of the delay to rate it consistently.

RESULTS

Subjective disturbance increased progressively with increasing delay and was a nonmonotonic function of low-frequency hearing loss. Subjects with mild or severe low-frequency hearing loss were generally less disturbed by the delay than those with moderate loss. Disturbance ratings tended to decrease over successive tests. Word production rates were not significantly affected by delay over the range of delays tested.

CONCLUSIONS

The results follow a pattern similar to those presented in , obtained using a simulation of hearing loss and normally hearing subjects, except for the nonmonotonic variation of disturbance with low-frequency hearing loss. We hypothesize that disturbance is maximal when the levels in the ear canal of the low-frequency components are similar for the unaided and aided sounds. A rating of 3, which is probably just acceptable, was obtained for delays ranging from 14 to 30 msec, depending on the hearing loss. Some acclimatization to the subjective disturbance occurred over a time scale of about 1 hour.

A revised model of loudness perception applied to cochlear hearing loss

We previously described a model for loudness perception for people with cochlear hearing loss. However, that model is incompatible with our most recent and most satisfactory model of loudness for normal hearing. Here, we describe a loudness model that is applicable to both normal and impaired hearing. In contrast to our earlier model for impaired hearing, the new model correctly predicts: (1) that a sound at absolute threshold has a small but finite loudness; (2) that, for levels very close to the absolute threshold, the rate of growth of loudness is similar for normal ears and ears with cochlear hearing loss; (3) the relation between monaural and binaural threshold and loudness; (4) recent measures of equal-loudness contours. Like the earlier model, the new model can account for the loudness recruitment and reduced loudness summation that are typically associated with cochlear hearing loss.