Simulated Hearing Loss Research Articles

Reliability of electric response audiometry using 80 Hz auditory steady-state responses

The reliability of the Auditory Steady State Response (ASSR) has not been thoroughly evaluated despite its recent application as a clinical tool for threshold estimation. The purpose of this study was to examine test-retest (TR) reliability of ASSR threshold estimates in an empirical research design. The ASSR, tested using modulation frequencies approximately 80 Hz and above, was evaluated against pure tone audiometry (PTA), and the slow vertex potential (SVP, N1-P2). Sixteen normal-hearing young female adults were tested twice, one week apart. Varying degrees of sensorineural hearing loss of a notched configuration were simulated with filtered masking noise. Test-retest reliability was assessed using Pearson-product moment correlation analysis, supplemented by other post-hoc analyses. Results demonstrated moderately strong TR reliability for ASSR at 1000, 2000 and 4000 Hz (r = 0.83–0.93); however, the reliability of ASSR at 500 Hz was weaker (r = 0.75). Results suggest that ASSR-ERA is a reliable test at mid–high frequencies, at least with the configuration and degrees of simulated sensorineural hearing loss examined in this study.

Interactive Effects of High-Pass Filtering and Masking Noise on Word Recognition

This study sought to examine the word recognition performance in noise of individuals with a simulated low-frequency hearing loss. The goal was to understand how low-frequency hearing impairment affects performance on tasks that challenge temporal processing skills. Twenty-two normal-hearing young adults participated. Monosyllabic words were presented in continuous and interrupted noise at 3 signal-to-noise ratios of -10, 0, and +10 dB. High-pass filtering of the stimuli at 3 different cutoff frequencies (ie, 1,000, 1,250, and 1,500 Hz) simulated the low-frequency hearing impairment. In general, performance decreased with increasing cutoff frequency, was higher for more favorable signal-to-noise ratios, and was superior in the interrupted condition relative to the continuous noise condition. One important revelation was that the magnitude of the performance superiority observed in the interrupted noise condition did not diminish with high-pass filtering; ie, the release from masking in interrupted noise was preserved. The results of the present study complement previous findings in which this paradigm was used with low-pass filtering to simulate a high-frequency hearing loss. That is to say, low-frequency hearing channels are inherently poorer than high-frequency channels in temporal resolution.

Vowel perception by noise masked normal-hearing young adults

This study examined vowel perception by young normal-hearing (YNH) adults, in various listening conditions designed to simulate mild-to-moderate sloping sensorineural hearing loss. YNH listeners were individually age- and gender-matched to young hearing-impaired (YHI) listeners tested in a previous study [Richie et al., J. Acoust. Soc. Am. 114, 2923-2933 (2003)]. YNH listeners were tested in three conditions designed to create equal audibility with the YHI listeners; a low signal level with and without a simulated hearing loss, and a high signal level with a simulated hearing loss. Listeners discriminated changes in synthetic vowel tokens /I e epsilon alpha ae/ when Fl or F2 varied in frequency. Comparison of YNH with YHI results failed to reveal significant differences between groups in terms of performance on vowel discrimination, in conditions of similar audibility by using both noise masking to elevate the hearing thresholds of the YNH and applying frequency-specific gain to the YHI listeners. Further, analysis of learning curves suggests that while the YHI listeners completed an average of 46% more test blocks than YNH listeners, the YHI achieved a level of discrimination similar to that of the YNH within the same number of blocks. Apparently, when age and gender are closely matched between young hearing-impaired and normal-hearing adults, performance on vowel tasks may be explained by audibility alone.

Effect of Slow-Acting Wide Dynamic Range Compression on Measures of Intelligibility and Ratings of Speech Quality in Simulated-Loss Listeners

The purpose of this study was twofold: (a) to determine the extent to which 4-channel, slow-acting wide dynamic range amplitude compression (WDRC) can counteract the perceptual effects of reduced auditory dynamic range and (b) to examine the relation between objective measures of speech intelligibility and categorical ratings of speech quality for sentences processed with slow-acting WDRC. Multiband expansion was used to simulate the effects of elevated thresholds and loudness recruitment in normal hearing listeners. While some previous studies have shown that WDRC can improve both speech intelligibility and quality, others have found no benefit. The current experiment shows that moderate amounts of compression can provide a small but significant improvement in speech intelligibility, relative to linear amplification, for simulated-loss listeners with small dynamic ranges (i.e., flat, moderate hearing loss). This benefit was found for speech at conversational levels, both in quiet and in a background of babble. Simulated-loss listeners with large dynamic ranges (i.e., sloping, mild-to-moderate hearing loss) did not show any improvement. Comparison of speech intelligibility scores and subjective ratings of intelligibility showed that listeners with simulated hearing loss could accurately judge the overall intelligibility of speech. However, in all listeners, ratings of pleasantness decreased as the compression ratio increased. These findings suggest that subjective measures of speech quality should be used in conjunction with either objective or subjective measures of speech intelligibility to ensure that participant-selected hearing aid parameters optimize both comfort and intelligibility.

Tolerable Hearing-Aid Delays: IV. Effects on Subjective Disturbance During Speech Production by Hearing-Impaired Subjects

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. 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. 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. 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.

Comparison of hearing loss compensation algorithms using speech intelligibility measures

Sensorineural hearing loss includes loss of high-frequency sensitivity which results in decreased speech intelligibility. The loss cannot be compensated by inverting the audiogram because of the non-linear effects of sensorineural hearing loss (frequency smearing, decreased dynamic range, decreased time-frequency resolution). Several non-linear compensation schemes exist (Half-gain, POGO, NAL-R, Fig. 6, DSL and LGOB) and this paper provides a comparison of those using the objective Perceptual Evaluation of Subjective Quality (PESQ) score and the subjective Hearing In Noise Test (HINT). The listening tests were run on 15 unaided hearing impaired listeners as well as 15 normal hearing listeners using a simulated hearing loss algorithm. These results show marked improvement in intelligibility for the compensated speech over the normal speech for both normal and hearing impaired adults.

Diagnosis and Follow-up of Hearing Loss in Infants

Diagnosis and Follow-up of Hearing Loss in Infants

Auditory brainstem and middle latency responses to 1 kHz tones in noise-masked normally-hearing and sensorineurally hearing-impaired adults

The present study provides comparative evaluation of the ABR and MLR to 1 kHz brief tones in two groups of hearing-impaired subjects (noise-masked normally-hearing; and sensorineurally hearing-impaired adults), as well as a normally-hearing control group. Tones were presented at intensities from threshold to 80–90 dB nHL. The results of this study show that: (1) the ABR and MLR to these low-frequency (1 kHz) tones are equally accurate in estimating hearing threshold, (2) at supra-threshold levels, there are differences in the ABRs and MLRs for subjects with decreased hearing sensitivity resulting from cochlear pathology, compared to those obtained from adults with simulated hearing loss due to broadband masking, and (3) supra-threshold stimuli produce differential effects on the latency and amplitude characteristics of the ABR and MLR in listeners with true sensorineural hearing impairments. Possible physiologic explanations are offered for this differential pattern of results.

Immersive simulation of hearing loss and auditory prostheses

Simulation of hearing loss is useful for demonstrating the communication challenges facing hearing-impaired people. However, current simulations, most of which are only recordings, do not actually elevate thresholds; i.e., they do not simulate hearing loss, per se. The hearing loss simulator described in this talk is immersive; the user’s detection thresh- olds for ambient sounds are shifted by a prescribed degree. This threshold shift is achieved through a combination of passive attenuation (from muff-type hearing protectors) and additive masking noise (introduced by within-muff earphones). Acoustic signals picked up by microphones near each ear are processed through bandpass AGC channels and delivered via the earphones to complete the simulation of frequency-dependent hearing loss and loudness recruitment. Preliminary results validating the accuracy of specified threshold shift will be presented, along with speech-reception data comparing simulated with actual hearing losses. Subjective reactions of users engaged in one-on-one conversation suggest that strong feelings of communication disability are engendered by even moderate degrees of simulated hearing loss. The system, which is capable of simulating any degree of recruiting hearing loss along with hearing aids or cochlear implants, can provide effective interactive demonstrations of both auditory communication handicap and rehabilitation options. [Work supported by NIDCD.]

Simulated Hearing Loss via Masking: Research and Heuristic Applications

The traditional view of masking is the effective exclusion of the nontest ear in conventional behavioral audiometry. Various other applications, however, are possible, including evaluations of auditory evoked potentials. General concepts of masking in psychoacoustic and electrophysiologic testing are reviewed, leading to a detailed summary of new techniques developed to improve the diagnostic power of the auditory-brain-stem response (ABR) test in the detection of eighth-nerve testing-the “stacked ABR.” Another application is the use of filter-shaped noise to simulate hearing loss of particular degree and configuration in normal listeners to assess the accuracy of estimates of hearing loss using electric response audiometry (ERA) and test-retest reliability of a given method of ERA. This article reports on the preliminary results of a study on a recently developed method of ERA based on measurement of the auditory steady-state responses (ASSR). These results demonstrate similar estimates of hearing loss among the measures examined-pure-tone audiometry, ERA using the slow vertex potential, and ERA using the ASSR-although ERA estimates tend to exaggerate the loss by several decibels, even in a highly controlled study. Finally, simulated hearing loss is suggested as a tool for the training of audiologists in methods of both behavioral and electric response audiometry, wherein the instructor can provide a variety of degrees and configurations of hearing loss in a highly predictable manner.

Simulated conductive hearing loss in children.

Otitis media with effusion (OME) often results in hearing loss for children with the condition. In order to provide appropriate and effective audiologic management, it is important to understand the impact of OME on speech recognition ability when hearing loss is present. This study examined the speech recognition abilities of normal-hearing six- and seven-year-old children (n = 12) and adults (n = 12) using monosyllabic words and nonsense syllables presented at two levels of simulated conductive hearing loss characteristic of OME. Average speech recognition scores decreased as the degree of simulated conductive hearing loss increased. Both age groups scored significantly poorer for nonsense syllables than for monosyllabic words. In general, the children performed more poorly than the adults with the exception of the easiest listening condition for word stimuli. Furthermore, children appeared less able than adults to use their knowledge of familiar words to improve performance. These findings suggest that rehabilitative strategies may best be focused on combining familiarization techniques and amplification options.

Counseling the significant other in the hearing aid purchase process

In Brief A patient's significant other (SO) often exerts a major influence on the hearing aid purchase decision. Findings are reported on the effectiveness of a hearing loss simulator in demonstrating to the SO what the patient is experiencing and why amplification may be the answer.

Interactive Effects of Low–Pass Filtering and Masking Noise on Word Recognition

A word recognition in noise paradigm was employed to examine temporal resolution in individuals with simulated hearing loss. Word recognition scores were obtained for low-pass filtered speech (i.e., cutoff frequencies of 1000,1250, and 1500 Hz) presented in continuous and interrupted noise at signal-to-noise ratios (SNRs) of -10, 0, and 10 dB. Performance improved with increasing SNR and low-pass frequency filter settings. Generally, word recognition performance was better in the interrupted noise condition than the continuous noise condition. This effect was greatest in the -10 dB SNR condition. Since the continuous/interrupted performance difference steadily declined as a function of low-pass filter cutoff frequency, these findings suggest that one factor leading to poorer speech recognition in individuals with high-frequency hearing impairment may be their dependence on low-frequency hearing channels that are inherently poorer than high-frequency channels for temporal resolution.

An evaluation of an electronic simulation of hearing impairment in the training of mainstream teachers

This paper describes an evaluation of a simple electronic simulation of sensorineural hearing loss intended to raise the awareness of mainstream trainee teachers during role play as both teacher and hearing-impaired pupil. In the wake of the continuing commitment to integration, it is hoped that such a device can improve the preparation of mainstream trainee teachers for their role as teachers of the hearing impaired. Twenty-four trainee teachers experienced both roles during the simulation, and their comments were scored by an expert panel for their importance. It was found that participants achieved a significant increase in awareness during their two five-minute simulated experiences of being a hearing pupil and teaching a hearing-impaired pupil. The experience of learning as a pupil with a simulated impairment was demonstrated to be as valuable as teaching a pupil with a simulated impairment, although there were differences with respect to the types of issues highlighted.

Speech intelligibility and listener preferences for amplitude-compressed speech: Speech-based STI predictions and measurements on listeners with simulated hearing loss

Relations between objective intelligibility scores, subjective pleasantness ratings, and estimates of the STI for speech processed by multi-band amplitude compression systems were studied in normal-hearing listeners with simulated hearing loss. STI estimates were based on modulation spectrum changes in the processed speech signals [Payton and Braida, J. Acoust. Soc. Am. 106, 3637–3648 (1999)]. Linear amplification and two syllabic compression conditions were tested with and without two backgrounds: Speech-spectrum noise and restaurant babble. Signals were compressed independently in four nonoverlapping frequency bands with compression ratios of two and three, and attack and release times of 20 and 200 ms, respectively. The NAL-R formula determined output frequency-gain characteristics. Flat, 50 dB, sensorineural hearing losses were simulated in normal-hearing listeners via multiband expansion [Duchnowski and Zurek, J. Acoust. Soc. Am. 98, 3170–3181 (1995)]. Speech intelligibility and pleasantness ratings were obtained. All conditions were also evaluated using the modified STI. The STI predicted speech in restaurant babble would be more intelligible than speech in noise for each compression condition. The data reflected this for the two compression conditions. The STI predictions were also consistent with pleasantness ratings: Linear amplification was the most pleasant compression condition. [This work supported by NIDCD.]

Basic science at the intersection of speech science and communication disorders

In this introduction to this special issue of the Journal of Phonetics, the concept of generalization of scientific explanations across normal individuals and individuals with identified clinical disorders that affect speech production and perception is discussed. Papers dealing with speech production in persons with hearing impairment, aphasia, dysarthria, voice disorders, and structural modifications of the vocal tract, as well as simulations of hearing loss and lexicons show how data from speech and hearing disorders may inform theory about normal processes. In this context, clinical disorders are seen as opportunities for basic scientific research. Associated with these opportunities are potential pitfalls for scientific experimental design. Chief among such pitfalls is the loss of randomized selection of individuals for experimental study. The effect of this problem on experimental design is discussed along with some suggestions for alternative research designs and methods for incorporating results from clinical disorders in basic scientific explanations.

Perception of speech and non-speech sounds by listeners with real and simulated sensorineural hearing loss

The effects of sensorineural and simulated hearing loss on the perception of speech and non-speech sounds are evaluated and compared. Two simulations of hearing loss are considered: one introduces additive masking noise to elevate the detection thresholds of listeners with normal hearing, the other applies multiband dynamic expansion to attenuate sound components towards these detection thresholds. Measures of speech perception are derived from intelligibility tests for consonant-vowel syllables presented in a background of speech-spectrum noise. The perception of non-speech sounds was evaluated through measurements of the detection of tones in quiet and in the presence of broadband and narrowband masking noise, psychoacoustic tuning curves measured under forward masking conditions, and intensity discrimination for tone pulses. For mild and moderate hearing losses, both types of simulation alter the perception of speech in noise in a manner similar to sensorineural impairment. These simulations also produce effects similar to sensorineural impairment on the detection of tones in quiet and on simultaneous and forward masking. The expansion simulation tends to improve the ability to discriminate tone intensities, an effect generally not seen in listeners with sensorineural impairments.

Forward masking in normal-hearing, hearing-impaired, and noise-masked normal listeners

This study examined forward-masking functions in normal-hearing, hearing-impaired, and noise-masked normal listeners using a 300-ms, one-octave 80 dB SPL masker centered at 4000 Hz and a 20-ms, 4000-Hz pure-tone signal. Thresholds were measured as a function of interstimulus interval (0 to 150 ms), and a time constant (τ) was estimated from the best exponential fit to this function. No significant differences were found between τ values obtained from the normal-hearing (mean: 44 ms) and hearing-impaired (mean: 45 ms) subjects. Thus, temporal resolution in this task was not worse for the impaired listeners than for the normal listeners. Under the noise-masked condition, normal-hearing subjects completed the forward-masking task in the presence of a continuous 4000-Hz, one-octave noise, whose level was chosen to shift each subject’s threshold to match that of a hearing-impaired subject of equivalent age and gender. The mean τ value obtained in the noise-masked condition was 8 ms, which was significantly smaller than the τ values obtained from either group in the absence of a background masker. This curious finding suggests that use of a continuous noise masker to simulate hearing loss is not effective in this temporal resolution task. [Work supported by NIDCD.]

The CON-SOT-LOT Test for Nonorganic Hearing Loss

The efficacy of a screening procedure for detecting nonorganic hearing loss using standard audiometric instrumentation was examined. Thirty normal-hearing subjects' responses to continuous and standard and lengthened off-time pulsed tones, using an ascending-descending method, were compared. Subjects were asked to respond to test stimuli in normal-hearing and simulated hearing loss conditions. Data show that there are clinical and statistical differences between subjects' response patterns in the normal-hearing condition as compared to the feigned hearing loss condition. The procedure is offered as a simple method of screening for nonorganic hearing loss.

Parental perceptions of hearing loss classification in children.

Hearing loss classification scales are commonly used to explain audiometric findings to the parents of children with hearing loss. These scales, however, have little or no scientific basis. In this study, filtered auditory recordings were used to simulate three levels of childhood hearing loss, as defined by the commonly used terms--slight, mild, and moderate. Parents, after listening to each simulation, were asked to provide their impressions. Results demonstrated that: parents defined each simulated loss with terminology representing substantially greater magnitude than the commonly used terms; parents anticipated significantly greater difficulty (p < .05) for each of nine hearing-related tasks when hearing loss was defined by the simulations rather than the classification terms; and parents selected more aggressive management procedures in response to the simulations than to the classification terms. In an additional task, parents estimated degree of simulated hearing loss with percentage values, indicating about 40% greater hearing loss for the three levels of loss compared to values produced by the conventional American Academy of Otolaryngology-American Council of Otolaryngology (1979) percentage formula. The findings indicate that standard methods of classifying hearing loss in audiologic and medical clinics may undermine parents' understanding of their child's hearing loss, causing them to underestimate substantially the magnitude of the loss.