Examining the Use and Benefits of Low-/Mild-Gain Hearing Aids in Service Members with Normal Hearing Thresholds and Self-Reported Hearing Difficulties.

Low- (or mild-) gain hearing aids (LGHAs) are increasingly considered for individuals with normal peripheral hearing but significant self-reported hearing difficulties (SHDs). This study assesses the benefits of LGHAs as a management option for individuals with normal hearing thresholds (NHTs) and SHDs, comparing LGHA use and benefit to individuals with non-significant hearing difficulties (NHDs) and those with peripheral hearing loss. Questionnaires addressing hearing aid usage, benefit, hearing difficulties, and tinnitus were administered to 186 individuals who self-identified as hearing aid users in a sample of 6652 service members who were receiving their annual hearing tests. Participants were divided into SHD and NHD groups based on the normative cutoff of the Tinnitus and Hearing Survey-Hearing Subscale (THS-H), and into hearing impairment (HI) and NHT based on their audiometric air-conduction thresholds. Individuals with SHDs and NHTs reported higher LGHA usage and benefit than individuals with NHDs and NHTs. Comparable use and benefit were noted between groups with SHDs regardless of peripheral hearing loss status. The findings support LGHAs as a suitable management option for individuals with NHTs and SHDs, as indicated by hearing aid use and benefit. Quantifying the level of perceived auditory processing deficits (i.e., SHDs), notably with the THS-H, enhances sensitivity in identifying those who may benefit the most from this treatment option.

The Effects of Signal to Noise Ratio, T60 , Wide-Dynamic Range Compression Speed, and Digital Noise Reduction in a Virtual Restaurant Setting.

OBJECTIVES: Hearing aid processing in realistic listening environments is difficult to study effectively. Often the environment is unpredictable or unknown, such as in wearable aid trials with subjective report by the wearer. Some laboratory experiments create listening environments to exert tight experimental control, but those environments are often limited by physical space, a small number of sound sources, or room absorptive properties. Simulation techniques bridge this gap by providing greater experimental control over listening environments, effectively bringing aspects of the real-world into the laboratory. This project used simulation to study the effects of wide-dynamic range compression (WDRC) and digital noise reduction (DNR) on speech intelligibility in a reverberant environment with six spatialized competing talkers. The primary objective of this study was to determine the efficacy of WDRC and DNR in a complex listening environment using virtual auditory space techniques. DESIGN: Participants of greatest interest were listeners with hearing impairment. A group of listeners with clinically normal hearing was included to assess the effects of the simulation absent the complex effects of hearing loss. Virtual auditory space techniques were used to simulate a small restaurant listening environment with two different reverberation times (0.8 and 1.8 sec) in a range of signal to noise ratios (SNRs) (-8.5 to 11.5 dB SNR). Six spatialized competing talkers were included to further enhance realism. A hearing aid simulation was used to examine the degree to which speech intelligibility was affected by slow and fast WDRC in conjunction with the presence or absence of DNR. The WDRC and DNR settings were chosen to be reasonable estimates of hearing aids currently available to consumers. RESULTS: A WDRC × DNR × Hearing Status interaction was observed, such that DNR was beneficial for speech intelligibility when combined with fast WDRC speeds, but DNR was detrimental to speech intelligibility when WDRC speeds were slow. The pattern of the WDRC × DNR interaction was observed for both listener groups. Significant main effects of reverberation time and SNR were observed, indicating better performance with lower reverberation times and more positive SNR. CONCLUSIONS: DNR reduced low-amplitude noise before WDRC-amplified the low-intensity portions of the signal, negating one potential downside of fast WDRC and leading to an improvement in speech intelligibility in this simulation. These data suggest that, in some real-world environments that include both reverberation and noise, older listeners with hearing impairment may find speech to be more intelligible if DNR is activated when the hearing aid has fast compression time constants. Additional research is needed to determine the appropriate DNR strength and to confirm results in wearable hearing aids and a wider range of listening environments.

Updating the Spectral Correlation Index: Integrating Audibility and Band Importance Using Speech Intelligibility Index Weights.

The original Spectral Correlation Index (SCIo ) is a measure of amplitude envelope distortion that has been used in several studies to predict behavioral results. Because the original SCIo did not account for the differential contribution of particular frequency bands to speech intelligibility (i.e., band importance) or for audibility, a new "individual" version (the SCIi ) is proposed and evaluated. Sentence intelligibility data are used to compare the predictive power and goodness-of-fit for statistical models using two versions of the SCI. The SCIi provides significantly better fits to behavioral data than the SCIo . This result demonstrates the importance of accounting for and including signal audibility in analyzing and modeling data collected from the population of individuals with hearing impairment. With this update, the SCIi is a useful measure for predicting speech intelligibility based on amplitude envelope distortions.

Using Machine Learning and the National Health and Nutrition Examination Survey to Classify Individuals With Hearing Loss.

Even before the COVID-19 pandemic, there was mounting interest in remote testing solutions for audiology. The ultimate goal of such work was to improve access to hearing healthcare for individuals that might be unable or reluctant to seek audiological help in a clinic. In 2015, Diane Van Tasell patented a method for measuring an audiogram when the precise signal level was unknown (patent US 8,968,209 B2). In this method, the slope between pure-tone thresholds measured at 2 and 4 kHz is calculated and combined with questionnaire information in order to reconstruct the most likely audiograms from a database of options. An approach like the Van Tasell method is desirable because it is quick and feasible to do in a patient's home where exact stimulus levels are unknown. The goal of the present study was to use machine learning to assess the effectiveness of such audiogram-estimation methods. The National Health and Nutrition Examination Survey (NHANES), a database of audiologic and demographic information, was used to train and test several machine learning algorithms. Overall, 9,256 cases were analyzed. Audiometric data were classified using the Wisconsin Age-Related Hearing Impairment Classification Scale (WARHICS), a method that places hearing loss into one of eight categories. Of the algorithms tested, a random forest machine learning algorithm provided the best fit with only a few variables: the slope between 2 and 4 kHz; gender; age; military experience; and self-reported hearing ability. Using this method, 54.79% of the individuals were correctly classified, 34.40% were predicted to have a milder loss than measured, and 10.82% were predicted to have a more severe loss than measured. Although accuracy was low, it is unlikely audibility would be severely affected if classifications were used to apply gains. Based on audibility calculations, underamplification still provided sufficient gain to achieve ~95% correct (Speech Intelligibility Index ≥ 0.45) for sentence materials for 88% of individuals. Fewer than 1% of individuals were overamplified by 10 dB for any audiometric frequency. Given these results, this method presents a promising direction toward remote assessment; however, further refinement is needed before use in clinical fittings.

Reverberation strength perceived by normal-hearing listeners predictable based on time-varying binaural loudness.

Previous work has explored novel binaural combinations of reverberation and the resulting perceived reverberation strength (reverberance). The present study examines the perceptual effects of additional binaural combinations of reverberation with the goal of explaining reverberance in terms of basic psychoacoustic principles. Stimuli were generated using virtual space techniques simulating a speech source 3 m to the listener's right in a moderately reverberant environment. Reverberant energy at the ears was varied systematically relative to the natural level for the environment (0-dB gain). The method of magnitude estimation was used to estimate reverberance. Four experiments were conducted. Experiment 1 tested monaural listening conditions for both left and right ears at reverberation gains from -21 dB to 0 dB. Experiment 2 tested a binaural listening condition where only reverberant energy at the ear farther from the source was manipulated (-21 dB to 0 dB). Experiment 3 tested two binaural conditions over a wider range of reverberation gains (-18 dB to +24 dB). In one condition, reverberant energy was manipulated for both ears equally. In the other condition, reverberant energy was manipulated only for the ear nearer the source. In Experiment 4, reverberant tails of the stimuli were removed to test whether listeners were able to use ongoing reverberant information to judge reverberance. The results from all experiments were found to be well predicted by a model of time-varying binaural loudness that focused on "glimpses" in time with relatively high reverberant sound energy and low direct sound energy. These findings suggest that the mechanisms underlying reverberance and loudness may be similar.

The Effect of Hearing Loss on Localization of Amplitude-Panned and Physical Sources.

BACKGROUND: Clinics are increasingly turning toward using virtual environments to demonstrate and validate hearing aid fittings in "realistic" listening situations before the patient leaves the clinic. One of the most cost-effective and straightforward ways to create such an environment is through the use of a small speaker array and amplitude panning. Amplitude panning is a signal playback method used to change the perceived location of a source by changing the level of two or more loudspeakers. The perceptual consequences (i.e., perceived source width and location) of amplitude panning have been well-documented for listeners with normal hearing but not for listeners with hearing impairment. PURPOSE: The purpose of this study was to examine the perceptual consequences of amplitude panning for listeners with hearing statuses from normal hearing through moderate sensorineural hearing losses. RESEARCH DESIGN: Listeners performed a localization task. Sound sources were broadband 4 Hz amplitude-modulated white noise bursts. Thirty-nine sources (14 physical) were produced by either physical loudspeakers or via amplitude panning. Listeners completed a training block of 39 trials (one for each source) before completing three test blocks of 39 trials each. Source production method was randomized within block. STUDY SAMPLE: Twenty-seven adult listeners (mean age 52.79, standard deviation 27.36, 10 males, 17 females) with hearing ranging from within normal limits to moderate bilateral sensorineural hearing loss participated in the study. Listeners were recruited from a laboratory database of listeners that consented to being informed about available studies. DATA COLLECTION AND ANALYSIS: Listeners indicated the perceived source location via touch screen. Outcome variables were azimuth error, elevation error, and total angular error (Euclidean distance in degrees between perceived and correct location). Listeners' pure-tone averages (PTAs) were calculated and used in mixed-effects models along with source type and the interaction between source type and PTA as predictors. Subject was included as a random variable. RESULTS: Significant interactions between PTA and source production method were observed for total and elevation errors. Listeners with higher PTAs (i.e., worse hearing) did not localize physical and panned sources differently whereas listeners with lower PTAs (i.e., better hearing) did. No interaction was observed for azimuth errors; however, there was a significant main effect of PTA. CONCLUSION: As hearing impairment becomes more severe, listeners localize physical and panned sources with similar errors. Because physical and panned sources are not localized differently by adults with hearing loss, amplitude panning could be an appropriate method for constructing virtual environments for these listeners.

A dissociation between speech understanding and perceived reverberation.

As direct-to-reverberant energy ratio (DRR) decreases or decay time increases, speech intelligibility tends to decrease for both normal-hearing and hearing-impaired listeners. Given this relationship, it is easy to assume that perceived reverberation (reverberance) would act as an intermediary-as physical reverberation increases, so does reverberance, and speech intelligibility decreases as a result. This assumption has not been tested explicitly. Two experiments were conducted to test this hypothesis. In Experiment 1, listeners performed a magnitude estimation task, reporting reverberance for speech stimuli that were convolved with impulse responses whose reverberant properties were manipulated. Listeners reported a decrease in reverberance when the DRR was increased at both ears (Natural Room condition), but not when it was increased at only the ear nearest the source (Hybrid condition). In Experiment 2, listeners performed a speech intelligibility task wherein noise-masked speech was convolved with a subset of the impulse responses from Experiment 1. As predicted by the speech transmission index (STI), speech intelligibility was good in cases where at least one ear received non-reverberant speech, including the Hybrid listening condition in Experiment 1. Thus, the Hybrid listening condition resulted simultaneously in high reverberance (Exp. 1) and high speech intelligibility (Exp. 2), demonstrating that reverberance and speech intelligibility can be dissociated.

Speech perception adjusts to stable spectrotemporal properties of the listening environment.

When perceiving speech, listeners compensate for reverberation and stable spectral peaks in the speech signal. Despite natural listening conditions usually adding both reverberation and spectral coloration, these processes have only been studied separately. Reverberation smears spectral peaks across time, which is predicted to increase listeners' compensation for these peaks. This prediction was tested using sentences presented with or without a simulated reverberant sound field. All sentences had a stable spectral peak (added by amplifying frequencies matching the second formant frequency [F2] in the target vowel) before a test vowel varying from /i/ to /u/ in F2 and spectral envelope (tilt). In Experiment 1, listeners demonstrated increased compensation (larger decrease in F2 weights and larger increase in spectral tilt weights for identifying the target vowel) in reverberant speech than in nonreverberant speech. In Experiment 2, increased compensation was shown not to be due to reverberation tails. In Experiment 3, adding a pure tone to nonreverberant speech at the target vowel's F2 frequency increased compensation, revealing that these effects are not specific to reverberation. Results suggest that perceptual adjustment to stable spectral peaks in the listening environment is not affected by their source or cause.