Simulated Hearing Loss Research Articles

What do comparisons between younger and older adult listeners tell us about speech processing?

The perception of speech, the recognition of words, and the understanding of spoken language involve the dynamic and interactive processing of cues provided by the incoming signal and information stored in memory. Even when accuracy is high, the relative contributions of bottom-up and top-down processes may explain variations in the speed and effort required when listening to speech. Listening is fast when the quality of the incoming signal is optimal, but it is slowed as signal quality is reduced. Likewise, listening can be speeded when expectations constrain the likely alternatives or when priming implicitly facilitates the recognition of the signal, whereas it can be slowed if the context is incongruent with the signal or if context is used to resolve ambiguities or repair misperceptions in a compensatory fashion. Within-subjects comparisons on off-line and on-line measures in different listening conditions, including simulations of auditory aging and hearing loss, are used to investigate how listening effort varies and how listening is speeded or slowed depending on signal-driven and knowledge-driven factors. Comparisons between younger and older participants are used to evaluate how long-standing reductions in auditory temporal processing and compensatory changes in brain organization may alter how signal-driven and knowledge-driven processes interact.

System and method for immersive simulation of hearing loss and auditory prostheses

An immersive hearing loss and auditory prostheses simulator allows a person who listens through the simulation system to experience an actual shift in his or her thresholds for detecting ambient sounds, in a way that is similar to the shift in thresholds experienced by a hearing-impaired person. The simulator shifts the listener's thresholds while also processing the input signals for suprathreshold stimulation. With a controlled degree of auditory threshold shift with loudness recruitment, a hearing loss simulator is made valid and flexible.

A comparison of gap‐detection thresholds through audition and touch in listeners with real and simulated hearing impairment.

Gap‐detection thresholds were measured in listeners with real and simulated hearing loss under conditions of auditory or tactile presentation. The audiometric thresholds of each of ten listeners with sensorineural hearing loss (21–69 years of age) were simulated in groups of age‐matched normal‐hearing listeners through a combination of spectrally shaped masking noise and multiband expansion. The leading and trailing markers for the gap‐detection task were 250‐ and 400‐Hz sinusoids with a nominal duration of 100 ms. Gap‐detection thresholds for a nominal baseline gap of 0 ms were measured for four different combinations of leading and trailing markers (250–250, 250–400, 400–250, and 400–400 Hz) using a 3I, 2AFC procedure. Auditory measurements were obtained for monaural presentation over headphones using a marker level set to be equal to the maximum of 70 dB SPL or 10 dB SL. Tactile measurements were obtained using sinusoids presented to the left middle finger through an Alpha‐M AV‐6 vibrator at a level of 25 dB SL. Results are discussed in terms of (a) spectral‐disparity effects of leading and trailing markers; (b) relation of thresholds for auditory versus tactile presentation; and (c) comparisons of results from listeners with real and simulated hearing loss. [Work supported by NIH‐NIDCD R01 DC00117.]

Forward‐masking functions in listeners with real and simulated hearing loss.

Forward‐masking functions were obtained in eight listeners with moderate to severe sensorineural hearing loss (aged 21–69 years). The hearing loss of each impaired listener was simulated in a group of three age‐matched normal‐hearing listeners through a combination of spectrally shaped masking noise and multiband expansion. Forward masking was measured in both groups of listeners for probe signals at frequencies of 500, 1000, 2000, and 4000 Hz using an on‐frequency masker and two off‐frequency maskers (0.55 and 1.15 times the signal frequency) under a 3I, 2AFC procedure. The probe signal was presented at 5 dB SL; signals and maskers were gated with 5‐m on/off times with a steady‐state duration of 0 ms for probe signals and 100 ms for maskers; and values of masker‐offset time to signal‐onset time were in the range of 0 to 100 ms. Findings will be described in terms of the slopes of the masking functions for each combination of probe and masker frequency and the ratio of the slopes obtained with on‐ relativ...

Masking release for speech in listeners with real and simulated hearing impairment.

The current study examined the effects of audibility and age on the release of masking for speech in interrupted versus steady‐state noise in listeners with real and simulated hearing loss. The absolute thresholds of each of ten hearing‐impaired listeners were simulated in normal‐hearing listeners through a combination of spectrally shaped masking noise and multiband expansion for the octave bands with center frequencies from 0.25–8 kHz. Each individual hearing loss was simulated in two groups of three normal‐hearing listeners (one age‐matched group and one non‐age‐matched group). The speech‐to‐noise ratio (S/B) for 50%‐correct identification of HINT sentences was measured in backgrounds of steady‐state noise and temporally modulated (10‐Hz square‐wave) noise at two overall levels for unprocessed speech and for speech that was amplified with the NAL‐PR prescription. Results indicate that the magnitude of the release from masking (the difference in S/B obtained in steady‐state versus interrupted noise) observed in individual hearing‐impaired listeners was generally well produced in both groups of simulated‐loss listeners. Thus, release of masking appears to be determined primarily by audibility regardless of age. Predictions of masking release derived from the Speech Intelligibility Index (SII; ANSI S3.5‐1997) will be compared to the observed values. [Work supported by NIH‐NIDCD R01 DC00117.]

Infant-directed speech to infants with a simulated hearing loss.

The acoustic/phonetic features of infant-directed speech (IDS) were measured during face-to-face interactions between mothers and their six-month-old normal hearing infants (N=32) using a setup in which the mother and infant are seated in separate rooms and interact over their respective video monitors. There were two sound conditions, (i) a hearing condition in which infants could hear their mothers at 55 dB SPL, and (ii) a hearing loss condition in which the sound was turned off, and the infants could not hear their mothers. All mothers were told your baby cannot hear you. Mothers and infants interacted for 10 min using three labeled toys (sheep, shoe, and shark) to facilitate the production of exemplars of the corner vowels /i/, /u/, and /a/. The results showed that mean fundamental frequency (F0), F0 range, and the duration of the IDS vowels were comparable across the two conditions. However, vowel hyperarticulation was only evident in the hearing condition, not in the hearing loss condition. These results suggest that mothers adapt their speech input according to signs of infant responsiveness. That is, when their infant cannot hear them, they maintain their modifications to IDS F0 and duration, but at the expense of vowel hyperarticulation.

Temporal modulation transfer functions in listeners with real and simulated hearing loss.

Temporal modulation transfer functions in listeners with real and simulated hearing loss.

Effects of Speech Rate, Background Noise, and Simulated Hearing Loss on Speech Rate Judgment and Speech Intelligibility in Young Listeners

To study the effect of noise on speech rate judgment and signal-to-noise ratio threshold (SNR50) at different speech rates (slow, preferred, and fast). Speech rate judgment and SNR50 tasks were completed in a normal-hearing condition and a simulated hearing-loss condition. Twenty-four female and six male young, normal-hearing participants. Speech rate judgment was not affected by background noise regardless of hearing condition. Results of the SNR50 task indicated that, as speech rate increased, performance decreased for both hearing conditions. There was a moderate correlation between speech rate judgment and SNR50 with the various speech rates, such that as judgment of speech rate increased from too slow to too fast, performance deteriorated. These findings can be used to support the need for counseling patients and their families about the potential advantages to using average speech rates or rates that are slightly slowed while conversing in the presence of background noise.

Perception of speech simulating different configurations of hearing loss in normal hearing individuals

The present study aimed at assessing perception of filtered speech that simulated different configurations of hearing loss. The simulation was done by filtering four equivalent lists of a monosyllabic test developed by Shivaprasad for Indian‐English speakers. This was done using the Adobe Audition software. Thirty normal hearing participants in the age range of 17–25 years were evaluated. It was found that all four simulated configurations resulted in word identification scores that were significantly different from each other at the. 001 level. Further, phoneme error analysis was done, which showed place errors were more evident than manner and voicing errors in three of the simulated conditions (gradually falling, sharply falling, and rising configurations). It can be concluded that speech identification scores are dependent on the configuration of the simulated hearing loss. However, further studies need to be carried out on individuals with hearing impairment to determine whether a similar trend exists in them or not.

Review article: review of the literature on temporal resolution in listeners with cochlear hearing impairment: a critical assessment of the role of suprathreshold deficits.

A critical review of studies of temporal resolution in listeners with cochlear hearing impairment is presented with the aim of assessing evidence for suprathreshold deficits. Particular attention is paid to the roles of variables-such as stimulus audibility, overall stimulus level, and participant's age-which may complicate the interpretation of experimental findings in comparing the performance of hearing-impaired (HI) and normal-hearing (NH) listeners. On certain temporal tasks (e.g., gap detection), the performance of HI listeners appears to be degraded relative to that of NH listeners when compared at equal SPL (sound pressure level). For other temporal tasks (e.g., forward masking), HI performance is degraded relative to that of NH listeners when compared at equal sensation level. A relatively small group of studies exists, however, in which the effects of stimulus audibility and level (and occasionally participant's age) have been controlled through the use of noise-masked simulation of hearing loss in NH listeners. For some temporal tasks (including gap-detection, gap-duration discrimination, and detection of brief tones in modulated noise), the performance of HI listeners is well reproduced in the results of noise-masked NH listeners. For other tasks (i.e., temporal integration), noise-masked hearing-loss simulations do not reproduce the results of HI listeners. In three additional areas of temporal processing (duration discrimination, detection of temporal modulation in noise, and various temporal-masking paradigms), further studies employing control of stimulus audibility and level, as well as age, are necessary for a more complete understanding of the role of suprathreshold deficits in the temporal-processing abilities of HI listeners.

Use of Linear Frequency Transposition in Simulated Hearing Loss

To demonstrate the usability of new acoustic cues provided by a commercial hearing aid using linear frequency transposition. The importance of auditory training in realizing the benefit was evaluated. Quasi-experimental study design. All subjects were tested both with conventional amplification and with linear frequency transposition before and after directed training. A total of nine normal hearing participants with simulated high frequency hearing loss at and above 1600 Hz participated in the study. All subjects were native English speakers ranging in age from 18 to 24 years. Identification of voiceless phonemes in CV, VC, and CVC context processed with and without linear frequency transposition was evaluated. Identification test was carried out four times. Between test trials, participants completed 15 minutes of self-paced training using transposed stimuli. Prior to any training, transposition did not improve phoneme identification scores. Training of 30 minutes improved the overall identification scores of the transposed stimuli over the nontransposed stimuli by 14.4%. The results demonstrated that frequency transposition produces acoustic cues that normal hearing listeners with a simulated hearing loss at and above 1600 Hz may be trained to utilize.

Tolerable Hearing Aid Delays. V. Estimation of Limits for Open Canal Fittings

Open canal fittings are a popular alternative to close-fitting earmolds for use with patients whose low-frequency hearing is near normal. Open canal fittings reduce the occlusion effect but also provide little attenuation of external air-borne sounds. The wearer therefore receives a mixture of air-borne sound and amplified but delayed sound through the hearing aid. To explore systematically the effect of the mixing, we simulated with varying degrees of complexity the effects of both a hearing loss and a high-quality hearing aid programmed to compensate for that loss, and used normal-hearing participants to assess the processing. The off-line processing was intended to simulate the percept of listening to the speech of a single (external) talker. The effect of introducing a delay on a subjective measure of speech quality (disturbance rating on a scale from 1 to 7, 7 being maximal disturbance) was assessed using both a constant gain and a gain that varied across frequency. In three experiments we assessed the effects of different amounts of delay, maximum aid gain and rate of change of gain with frequency. The simulated hearing aids were chosen to be appropriate for typical mild to moderate high-frequency losses starting at 1 or 2 kHz. Two of the experiments used simulations of linear hearing aids, whereas the third used fast-acting multichannel wide-dynamic-range compression and a simulation of loudness recruitment. In one experiment, a condition was included in which spectral ripples produced by comb-filtering were partially removed using a digital filter. For linear hearing aids, disturbance increased progressively with increasing delay and with decreasing rate of change of gain; the effect of amount of gain was small when the gain varied across frequency. The effect of reducing spectral ripples was also small. When the simulation of dynamic processes was included (experiment 3), the pattern with delay remained similar, but disturbance increased with increasing gain. It is argued that this is mainly due to disturbance increasing with increasing simulated hearing loss, probably because of the dynamic processing involved in the hearing aid and recruitment simulation. A disturbance rating of 3 may be considered as just acceptable. This rating was reached for delays of about 5 and 6 msec, for simulated hearing losses starting at 2 and 1 kHz, respectively. The perceptual effect of reducing the spectral ripples produced by comb-filtering was small; the effect was greatest when the hearing aid gain was small and when the hearing loss started at a low frequency.

Delaware Approves Hearing Aid Benefit

Delaware Approves Hearing Aid Benefit

Prediction method for listening score and psychological impression taking into account hearing loss due to factors such as aging

This paper considers how the listening scores obtained for audio signals and psychological impressions for speech audibility change when factors such as hearing loss due to aging are taken into account. Concretely, frequency filters for simulating hearing loss due to factors such as aging are first prepared. Next, psychological listening experiments are conducted in which both the audio signal and the noise passing through the above-mentioned filters are transmitted to subjects with normal hearing. Using the observed experimental data, the relationships between the weighted-mean spectral distance and the listening scores of the audio signals and psychological impressions with respect to speech audibility are investigated. Next, based on these relationships, problems associated with the prediction of listening scores of audio signals and psychological impressions with respect to speech audibility are discussed. The predicted results are in good agreement with the observed values.

Auditory lifestyles and beliefs related to hearing loss among college students in the USA

The purpose of this study was to evaluate the auditory life styles and beliefs of college students with reference to exposure to loud sounds in the context of the health belief model. A survey was administered to 238 (40 men, 198 women) students in the USA. Results suggest that 44% of the students use noisy equipment without ear protection and 29% (69/238) of the students work in noisy environments. Of the 69 who worked in noisy surroundings, only ten reported wearing hearing protection devices although 50 (72.46%) reported tinnitus. The use of hearing protection devices (HPDs) was associated with previous experience with hearing loss and tinnitus. Although 75% of the students were aware that exposure to loud sounds could cause hearing loss, 50% of the students appeared to be exposing themselves to potentially harmful loud music. Furthermore, 46% of the students reported not using HPDs during loud musical activities because they felt that the music was difficult to hear with HPDs. Most students in this study considered hearing loss to be serious but 76% of the students believed that they would not lose their hearing until a greater age. Although 66% of the students had experienced tinnitus, 58% of these students reported not being concerned about it. These results suggest a critical need for promoting healthy hearing behavior among college students. Possible strategies could include improved education, experience with simulated hearing loss for extended periods and availability of cosmetically appealing or invisible HPDs with uniform attenuation across the frequency range.

Human Auditory Steady-State Responses During Sweeps of Intensity

To record steady-state responses to amplitude-modulated tones that change their intensity over time and to see how well behavioral thresholds can be estimated from such responses. The intensity of the stimuli used in this experiment increased from 25 to 75 dB SPL for 8 sec and then decreased back to 25 dB HL during the subsequent 8 sec. Responses to this intensity sweep were averaged and then analyzed using a short-time Fast-Fourier Transform to measure how the amplitude and phase of the responses changed with intensity. One experimental condition presented single 2-kHz tones to the left ear; a second condition examined the use of simultaneously presented multiple tones (0.5, 1, 2, and 4 kHz) to the left ear; a third condition used multiple tones presented dichotically; and a fourth condition presented the multiple dichotic tones in masking noise to simulate either low-frequency (less than 1400 Hz) or high-frequency (greater than 1400 Hz) hearing loss. Physiological thresholds were determined using six different algorithms and the relations between physiological and behavioral thresholds were evaluated to see how well behavioral thresholds could be estimated. The amplitude-intensity functions for the 1 and 2 kHz responses both demonstrated a plateau at higher intensities in the multiple-stimulus conditions but not in the single-stimulus condition. The slope of the amplitude-intensity functions varied significantly with the carrier frequency of the stimulus: 1.30 at 500 Hz, 0.87 at 1000 Hz, 0.75 at 2000 Hz, and 1.40 at 4000 Hz. The slope of the phase-intensity function averaged 1.16 degrees per dB and did not vary with carrier frequency. Estimates of latency, however, indicated that latency increased with decreasing carrier frequency and with decreasing intensity. The performance of the threshold estimating algorithms differed between normal hearing and simulated hearing loss, since the amplitude- and phase-intensity functions in the latter condition were not linear. Physiological-behavioral threshold differences were generally greater for normal hearing than for simulated hearing loss. Linear regression provided the least physiological-behavioral difference but was quite variable during simulated hearing loss. Simply defining threshold as the lowest intensity above which all responses were significantly different from residual EEG noise was the most accurate method in terms of yielding the least standard deviation of the physiological-behavioral difference with an average standard deviation of 10 dB, provided EEG noise levels were low enough in the normal hearing condition. Thresholds can be estimated using intensity sweeps with about the same accuracy as recording separate responses to discrete intensities. Sweep recordings provide additional information about the responses at suprathreshold intensities by clearly determining amplitude- and phase- intensity functions at these intensities.

Hearing loss and prosthesis simulation in audiology

Hearing loss and prosthesis simulation in audiology

Temporal jitter disrupts speech intelligibility: A simulation of auditory aging

We disrupted periodicity cues by temporally jittering the speech signal to explore how such distortion might affect word identification. Jittering distorts the fine structure of the speech signal with negligible alteration of either its long-term spectral or amplitude envelope characteristics. In Experiment 1, word identification in noise was significantly reduced in young, normal-hearing adults when sentences were temporally jittered at frequencies below 1.2 kHz. The accuracy of the younger adults in identifying jittered speech in noise was similar to that found previously for older adults with good audiograms when they listened to intact speech in noise. In Experiment 2, to rule out the possibility that the reductions in word identification were due to spectral distortion, we also tested a simulation of cochlear hearing loss that produced spectral distortion equivalent to that produced by jittering, but this simulation had significantly less temporal distortion than was produced by jittering. There was no significant reduction in the accuracy of word identification when only the frequency region below 1.2 kHz was spectrally distorted. Hence, it is the temporal distortion rather than the spectral distortion of the low-frequency components that disrupts word identification.

Factors affecting masking release for speech in modulated noise for normal-hearing and hearing-impaired listeners

The Speech Reception Threshold for sentences in stationary noise and in several amplitude-modulated noises was measured for 8 normal-hearing listeners, 29 sensorineural hearing-impaired listeners, and 16 normal-hearing listeners with simulated hearing loss. This approach makes it possible to determine whether the reduced benefit from masker modulations, as often observed for hearing-impaired listeners, is due to a loss of signal audibility, or due to suprathreshold deficits, such as reduced spectral and temporal resolution, which were measured in four separate psychophysical tasks. Results show that the reduced masking release can only partly be accounted for by reduced audibility, and that, when considering suprathreshold deficits, the normal effects associated with a raised presentation level should be taken into account. In this perspective, reduced spectral resolution does not appear to qualify as an actual suprathreshold deficit, while reduced temporal resolution does. Temporal resolution and age are shown to be the main factors governing masking release for speech in modulated noise, accounting for more than half of the intersubject variance. Their influence appears to be related to the processing of mainly the higher stimulus frequencies. Results based on calculations of the Speech Intelligibility Index in modulated noise confirm these conclusions.

Validity and accuracy of electric response audiometry using the auditory steady-state response: Evaluation in an empirical design

The validity and accuracy of the application of the auditory steady-state response (ASSR) to electric response audiometry (ERA) was tested further in a study permitting subjects to be their own controls for hearing loss. Simulated sensorineural hearing loss (SSHL) of complex configuration and varying degrees was effected using filtered masking noise. Thresholds estimated via ASSR-ERA were compared to those measured via conventional pure-tone audiometry. Further, the slow vertex potential N1–P2 was recorded to permit a comparison with an evoked-response test of common content validity and known accuracy. Results in a homogeneous subject sample demonstrated strong intertest correlation and agreement within 10 dB at 1000 to 4000 Hz (on average), but not at 500 Hz. The configurations determined by ASSR-ERA followed behavioral audiometric patterns well, except for the mildest degree of SSHL tested. Consequently, limitations of ERA remain, although ASSR-ERA appears to be quite valid overall and promises (justifiably) broad clinical applicability.