Experimental Hearing Aid Research Articles

Relationships between behavioural and self-report measures in speech recognition in noise

Objective Using data from the n200-study, we aimed to investigate the relationship between behavioural (the Swedish HINT and Hagerman speech-in-noise tests) and self-report (Speech, Spatial and Qualities of Hearing Questionnaire (SSQ)) measures of listening under adverse conditions. Design The Swedish HINT was masked with a speech-shaped noise (SSN), the Hagerman was masked with a SSN and a four-talker babble, and the subscales from the SSQ were used as a self-report measure. The HINT and Hagerman were administered through an experimental hearing aid. Study sample This study included 191 hearing aid users with hearing loss (mean PTA4 = 37.6, SD = 10.8) and 195 normally hearing adults (mean PTA4 = 10.0, SD = 6.0). Results The present study found correlations between behavioural measures of speech-in-noise and self-report scores of the SSQ in normally hearing individuals, but not in hearing aid users. Conclusion The present study may help identify relationships between clinically used behavioural measures, and a self-report measure of speech recognition. The results from the present study suggest that use of a self-report measure as a complement to behavioural speech in noise tests might help to further our understanding of how self-report, and behavioural results can be generalised to everyday functioning.

Is Having Hearing Loss Fundamentally Different? Multigroup Structural Equation Modeling of the Effect of Cognitive Functioning on Speech Identification.

Previous research suggests that there is a robust relationship between cognitive functioning and speech-in-noise performance for older adults with age-related hearing loss. For normal-hearing adults, on the other hand, the research is not entirely clear. Therefore, the current study aimed to examine the relationship between cognitive functioning, aging, and speech-in-noise, in a group of older normal-hearing persons and older persons with hearing loss who wear hearing aids. We analyzed data from 199 older normal-hearing individuals (mean age = 61.2) and 200 older individuals with hearing loss (mean age = 60.9) using multigroup structural equation modeling. Four cognitively related tasks were used to create a cognitive functioning construct: the reading span task, a visuospatial working memory task, the semantic word-pairs task, and Raven's progressive matrices. Speech-in-noise, on the other hand, was measured using Hagerman sentences. The Hagerman sentences were presented via an experimental hearing aid to both normal hearing and hearing-impaired groups. Furthermore, the sentences were presented with one of the two background noise conditions: the Hagerman original speech-shaped noise or four-talker babble. Each noise condition was also presented with three different hearing processing settings: linear processing, fast compression, and noise reduction. Cognitive functioning was significantly related to speech-in-noise identification. Moreover, aging had a significant effect on both speech-in-noise and cognitive functioning. With regression weights constrained to be equal for the two groups, the final model had the best fit to the data. Importantly, the results showed that the relationship between cognitive functioning and speech-in-noise was not different for the two groups. Furthermore, the same pattern was evident for aging: the effects of aging on cognitive functioning and aging on speech-in-noise were not different between groups. Our findings revealed similar cognitive functioning and aging effects on speech-in-noise performance in older normal-hearing and aided hearing-impaired listeners. In conclusion, the findings support the Ease of Language Understanding model as cognitive processes play a critical role in speech-in-noise independent from the hearing status of elderly individuals.

Influences of listener gender and working memory capacity on speech recognition in noise for hearing aid users

ABSTRACT This study aimed to: (1) examine the influence of working memory capacity on the ability of experienced hearing aid users to recognize speech in noise using new noise reduction settings, and (2) investigate whether male and female hearing aid users differ in their hearing sensitivity and ability to recognize aided speech in noisy environments. 195 experienced hearing aid users (113 males and 82 females, age range: 33–80 years) from the n200 project were investigated. The Hagerman test (capturing speech recognition in noise) was administered using an experimental hearing aid with two digital signal processing settings: (1) linear amplification without noise reduction (NoP), and (2) linear amplification with noise reduction (NR). Gender differences were analysed using a series of independent samples from t-tests on Hagerman sentence scores, and the pure-tone average thresholds across the frequencies 500, 1000, 2000, and 4000 Hz (PTA4) for the left ear and right ear were measured. Working memory capacity (WMC) was measured using a reading span test. A WMC grouping (high and low) was included as a between-group subject factor in the within-group factors ANOVA, NR settings (Nop, NR), noise type (steady state noise, four -talker babble), and level of performance (50%, 80%). Male listeners had better pure-tone thresholds than female listeners at frequencies 500 and 1000 Hz, whereas female listeners had better pure-tone thresholds at 4000 Hz. Female listeners showed significantly better speech recognition ability than male listeners on the Hagerman test with NR , but not with NoP . This gender difference was more pronounced at the 80% performance level than at the 50% level. WMC had a significant effect on speech recognition ability, and there was a two-way interaction between WMC grouping and level of performance. The examination of simple main effects revealed superior performance of listeners with higher WMC at 80% using new NR settings. WMC, rather than background noise, was the main factor influencing performance at 80%, while at 50%, background noise was the main factor. WMC was associated with speech recognition performance even after accounting for hearing sensitivity (PTA4). This is the first study to demonstrate that experienced male and female hearing aid users differ significantly in their hearing ability and sensitivity and ability to recognize aided speech in noise. Thus, the average female listener has a greater speech recognition ability than the average male listener when linear amplification with NR is applied, but not when NoP is activated. An average female listener hears a given sound with greater sensitivity compared with an average male listener at higher frequencies. WMC is an important factor in speech recognition in more challenging listening conditions (i.e., lower signal–noise ratio) for experienced hearing aid users using new NR settings. More investigation is needed for a better understanding of how gender affects the ability of listeners less experienced with hearing aids (such as younger and elderly hearing-impaired listeners) to recognize speech amplified with different signal processing, as gender differences may vary based on numerous factors, including the speaker’s gender and age.

Cognitive Processing Speed, Working Memory, and the Intelligibility of Hearing Aid-Processed Speech in Persons with Hearing Impairment.

Previous studies have demonstrated that successful listening with advanced signal processing in digital hearing aids is associated with individual cognitive capacity, particularly working memory capacity (WMC). This study aimed to examine the relationship between cognitive abilities (cognitive processing speed and WMC) and individual listeners’ responses to digital signal processing settings in adverse listening conditions. A total of 194 native Swedish speakers (83 women and 111 men), aged 33–80 years (mean = 60.75 years, SD = 8.89), with bilateral, symmetrical mild to moderate sensorineural hearing loss who had completed a lexical decision speed test (measuring cognitive processing speed) and semantic word-pair span test (SWPST, capturing WMC) participated in this study. The Hagerman test (capturing speech recognition in noise) was conducted using an experimental hearing aid with three digital signal processing settings: (1) linear amplification without noise reduction (NoP), (2) linear amplification with noise reduction (NR), and (3) non-linear amplification without NR (“fast-acting compression”). The results showed that cognitive processing speed was a better predictor of speech intelligibility in noise, regardless of the types of signal processing algorithms used. That is, there was a stronger association between cognitive processing speed and NR outcomes and fast-acting compression outcomes (in steady state noise). We observed a weaker relationship between working memory and NR, but WMC did not relate to fast-acting compression. WMC was a relatively weaker predictor of speech intelligibility in noise. These findings might have been different if the participants had been provided with training and or allowed to acclimatize to binary masking noise reduction or fast-acting compression.

Benefit From Directional Microphone Hearing Aids: Objective and Subjective Evaluations.

ObjectivesThe aims of this study were to find and compare the effect of directional (DIR) processing of two different hearing aids via both subjective and objective methods, to determine the association between the results of the subjective and objective evaluations, and to find out individual predictive factors influencing the DIR benefit.MethodsTwenty-six hearing aid users fitted unilaterally with each two different experimental hearing aid performed modified Korean Hearing in Noise Test (K-HINT) in three DIR conditions; omnidirectional (OMNI) mode, OMNI plus noise reduction feature, fixed DIR mode. In order to determine benefits from DIR benefit within a hearing aid and compare performance of the DIR processing between hearing aids, a subjective questionnaire was administrated on speech quality (SQ) and discomfort in noise (DN) domain. Correlation analysis of factors influencing DIR benefit was accomplished.ResultsBenefits from switching OMNI mode to DIR mode within both hearing aids in K-HINT were about 2.8 (standard deviation, 3.5) and 2.1 dB SNR (signal to ratio; SD, 2.5), but significant difference in K-HINT results between OMNI and OMNI plus noise reduction algorithm was not shown. The subjective evaluation resulted in the better SQ and DN scores in DIR mode than those in OMNI mode. However, the difference of scores on both SQ and DN between the two hearing aids with DIR mode was not statistically significant. Any individual factors did not significantly affect subjective and objective DIR benefits.ConclusionDIR benefit was found not only in the objective measurement performed in the laboratory but also in the subjective questionnaires, but the subjective results was failed to have significant correlation with the DIR benefit obtained in the K-HINT. Factors influencing individual variation in perceptual DIR benefit were still hard to explain.

Laboratory and Field Study of the Potential Benefits of Pinna Cue-Preserving Hearing Aids

The potential benefits of preserving high-frequency spectral cues created by the pinna in hearing-aid fittings were investigated in a combined laboratory and field test. In a single-blind crossover design, two settings of an experimental hearing aid were compared. One setting was characterized by a pinna cue-preserving microphone position, whereas the other was characterized by a microphone position not preserving pinna cues. Participants were allowed 1 month of acclimatization to each setting before measurements of localization and spatial release from speech-on-speech masking were completed in the laboratory. Real-world experience with the two settings was assessed by means of questionnaires. Seventeen participants with mild to moderate sensorineural hearing impairments completed the study. An inconsistent pinna cue benefit pattern was observed across the outcome measures. In the localization test, the pinna cue-preserving setting provided a significant mean reduction of 22° in the root mean square (RMS) error in the front-back dimension, with 13 of the 17 participants showing a reduction of at least 15°. No significant mean difference in RMS error between settings was observed in the left-right dimension. No significant differences between settings were observed in the spatial-unmasking test conditions. The questionnaire data indicated a small, but nonsignificant, benefit of the pinna cue-preserving setting in certain real-life situations, which corresponded with a general preference for that setting. No significant real-life localization benefit was observed. The results suggest that preserving pinna cues can offer benefit in some conditions for individual hearing-aid users with mild to moderate hearing loss and is unlikely to harm performances for the rest.

Preferred signal path delay and high-pass cut-off in open fittings

The combination of delayed sound from a digital hearing aid with direct sound through an open or vented fitting can potentially degrade the sound quality due to audible changes in timbre and/or perception of echo. The present study was designed to test a number of delay and high-pass combinations under worst-case (i.e. most sensitive) conditions. Eighteen normal-hearing and 18 mildly hearing-impaired subjects performed the test in a paired comparison (A/B) task. The subjects were asked to select a preferred setting with respect to sound quality. The test was set in an anechoic chamber using recorded speech, environmental sounds, and own voice. Experimental hearing aids were fitted binaurally with open domes thus providing maximum ventilation. The preference data were processed using a statistical choice model that derives a ratio-scale. The analysis indicated that in these test conditions there was no change in sound quality when varying the delay in the range 5–10 ms and that there was a preference for 2000 Hz high-pass filtering in most conditions, regardless of the hearing losses tested.SumarioLa combinación de sonido retrasado de un auxiliar auditivo con un sonido directo a través de una adaptación ventilada potencialmente puede degradar la calidad del sonido debido a cambios auditivos en timbre y/o la percepción de eco. El presente estudio fue designado para probar un número de retrasos y combinaciones pasa alto bajo las peores condiciones (i.e. las más sensibles). Dieciocho sujetos normales y 18 con hipoacusia superficial hicieron la prueba con comparación pareada (A/B). Se les pidió a los sujetos que escogieran su condición preferida con respecto a la calidad del sonido. La prueba se llevó a cabo en una cámara anecoica utilizando lenguaje grabado, sonidos ambientales y la propia voz. Se adaptaron auxiliares auditivos experimentales en forma binaural con cúpulas abiertas para máxima ventilación. Los datos preferidos fueron procesados utilizando un modelo de selección estadístico que deriva en una escala por ratios. El análisis indicó que en estas condiciones de prueba no hubo cambios en la calidad de sonido cuando se varió el retraso en el rango de 5–10 ms y que había una preferencia por la filtración pasa-alto de 2000Hz en la mayoría de condiciones , sin importar la hipoacusia en cuestión.

Effects of Acoustical Stimuli Delivered through Hearing Aids on Tinnitus

The use of acoustic signals to mask, mix with, or ease the distress associated with tinnitus has been clinically employed for decades. It has been proposed that expanding acoustic options for tinnitus sufferers due to personal preferences is desirable. Fractal tones incorporate many useful characteristics of music while avoiding certain features that could be distracting to some individuals. To assess the effects on relaxation, tinnitus annoyance, tinnitus handicap, and tinnitus reaction from the use of a hearing aid that incorporates combinations of amplification, fractal tones, and white noise. Participants listened to experimental hearing aids containing several acoustic options and were asked to rate the signals in terms of their effect on relaxation and tinnitus annoyance. They subsequently wore the hearing aids for 6 mo and completed tinnitus handicap and reaction scales. Fourteen hearing-impaired adults with primary complaints of subjective tinnitus. Participants were tested wearing hearing aids containing several programs including amplification only, fractal tones only, and a combination of amplification, noise, and/or fractal tones. The fractal tones (now commercially available as the "Zen" feature) were generated by the Widex Mind hearing aid. Rating procedures were conducted in the laboratory, and tinnitus reaction and handicap were assessed during and following a 6 mo field trial. Data were collected at the initial visit, one week, 1 mo, 3 mo, and 6 mo. Nonparametric statistics included Wilcoxon matched-pairs signed-rank, chi(2), and repeated-measures analyses of variance. Thirteen of 14 participants reported that their tinnitus annoyance, as measured by the Tinnitus Annoyance Scale, was reduced for at least one of the amplified conditions (with or without fractal tones or noise), relative to the unaided condition. Nine assigned a lower tinnitus annoyance rating when listening to fractal tones alone versus the amplification-alone condition. There was a range of preferences observed for fractal settings, with most participants preferring fractals with a slow or medium tempo and restricted dynamic range. The majority (86%) indicated that it was easier to relax while listening to fractal signals. Participants had preferences for certain programs and fractal characteristics. Although seven participants rated the noise-only condition as providing the least tinnitus annoyance, only two opted to have noise only as a program during the field trial, and none selected the noise-only condition as the preferred setting. Furthermore, while all four of the experienced hearing aid users selected noise as producing the least annoying tinnitus in the laboratory, only one selected it for field wear. Tinnitus Handicap Inventory and Tinnitus Reaction Questionnaire scores were improved over the course of the 6 mo trial, with clinically significant improvements occurring for over half of the participants on at least one of the measures. The results suggest that use of acoustic stimuli, particularly fractal tones, delivered though hearing aids can provide amplification while allowing for relief for some tinnitus sufferers. It is important to recognize, however, that tinnitus management procedures need to be supplemented with appropriate counseling.

Observations on Hearing Aid Users' Strategies for Controlling the Level of Their Own Voice

Evidence suggests that hearing-aid users have difficulties with own-voice level control, most likely because their auditory feedback is affected by hearing-aid amplification. The purpose of this study was to investigate how changes to auditory feedback affect the voice level of hearing-aid users. A correlational study was set up to investigate the relation between voice level and hearing-aid amplification. Seven hearing-impaired speakers participated. All were experienced hearing-aid users. The speakers projected their voice to a passive listener across different speaker-listener distances and with different prescriptions of gain in an experimental hearing aid. For each combination of conditions, produced voice level and self-perceived voice level was measured. These data were subjected to an analysis of variance assuming a mixture of random and fixed effects. In addition, all speakers took part in interviews. Three speakers reacted to the changes in auditory feedback in agreement with previous experiments with normal-hearing speakers: they compensated by changing produced voice level. In contrast, the voice levels in the other four speakers were largely unaffected by the changes to auditory feedback. A secondary observation was that while all speakers increased their voice level with distance, the two subgroups produced different growth rates of vocal level versus distance. It is hypothesized that the speakers in the former subgroup relied on auditory feedback for solving the experimental task, whereas the latter subgroup had developed an own-voice level-control strategy based on proprioceptory feedback, possibly because they have lost faith in their auditory feedback mechanism, which indeed is changed by both hearing loss and hearing-aid amplification. Comparison to "target" voice levels suggests that proprioceptory feedback is less effective than auditory feedback for achieving adequate level-distance growth rate.

Multichannel Compression Hearing Aids: Perceptual Considerations

Multichannel Compression Hearing Aids: Perceptual Considerations

Cognitive function in relation to hearing aid use

Two experiments were conducted to investigate possible relationships between cognitive function and hearing aid use. In Experiment 1, 72 first-time hearing aid users were tested for speech recognition in noise (Hagerman sentence test) with and without hearing aids. Cognitive function was assessed by tests of working memory (reading span test) and verbal information-processing speed. The results indicate that, after controlling for age and hearing loss, significant correlations exist between the measures of cognitive performance and speech recognition in noise, both with and without hearing aids. High cognitive performance was associated with high performance in the speech recognition task. In Experiment 2. 17 first-time hearing aid users with either high or low working-memory capacity tested an experimental hearing aid which processed the sound differently depending on whether or not speech was detected. The results revealed that those with high working-memory capacity were better than those with low capacity at identifying and reporting the specific processing effects of the aid. This may have implications for how reported results should be interpreted in a research context, how a person's rehabilitation needs are formulated, and how hearing aid controls should be supervised. In conclusion, careful attention should be paid to the cognitive status of listeners, as it can have a significant influence on their ability to utilize their hearing aids.

A high performance wearable signal processor system for the evaluation of digital hearing aid algorithms

Today’s commercially available digital hearing aids contain specialized hardware to keep the power consumption low. These specialized processors are not able to run arbitrary signal processing strategies. However, new audiological algorithms have to be assessed in the everyday acoustical environment of the hearing impaired before developing specialized hardware. Therefore, flexible experimental hearing aids, which include general purpose signal processors, are needed for R&D purposes. Such a system has been developed, based on the high performance signal processor Motorola DSP56303. The wearable signal processor units also include high-quality stereo analog-to-digital (ADC) and digital-to-analog (DAC) converters with 20-bit word length each. The available dynamic range exceeds 90 dB. The input and output gain can be adjusted by digital potentiometers. The housing of the device is small enough to carry the experimental hearing aid in a pocket (dimensions 150×80×25 mm). Software tools have been developed to ease the development of new algorithms. A set of configurable modules implements all hardware-dependent software routines and gives easy access to the peripherals and interfaces. A comfortable fitting interface allows easy control of the signal processing unit from a PC, even by assistant personnel. Thus the unit is best suited for use in interdisciplinary research projects.

Effects of reducing low-frequency amplification on consonant perception in quiet and noise.

The aim of this study was to assess the effect of low-frequency amplification on speech recognition performance by hearing-impaired listeners. Consonant identification performance by subjects with flat hearing losses and high-frequency hearing losses was assessed in three different hearing aid conditions, in quiet and noise. The experimental hearing aids all provided extra high-frequency amplification but differed in the amount of low-frequency amplification. The results showed that listeners with flat hearing losses benefited by low-frequency amplification, whereas subjects with high-frequency hearing losses exhibited deteriorating scores in conditions with greatest low-frequency amplification. Analyses of phonetic feature perception and individual consonant recognition scores revealed subtle interactions between hearing loss configuration and amplification contour.

Fundamental frequency and formant structure in deaf speech: Influence of a hearing aid in a case study

The importance of auditory monitoring for speech production is well established, particularly as evidenced by the effect of hearing loss on speech. Relatively abrupt changes in speech production have been noted in a hearing-impaired individual with an unusual hearing profile when she uses a “translating” hearing aid. The subject who produced the speech samples exhibits a severe to profound sensorineural hearing loss on traditional audiometric testing (125–800 Hz). Her acuity improves with frequency, such that her thresholds are normal in the range from 11 000 to 14 000 Hz. She has been fitted with an experimental hearing aid which transposes sound upward in frequency to the range where she hears best. Speech samples were obtained with and without the translating hearing aid. Materials used for analysis in the present study were sentences. The vowels /i/, /a/, and /u/, occurring in a variety of consonantal contexts, were analyzed spectrographically. The results indicate a systematic downward shift in fundamental frequency in the aided condition. Additionally, articulatory parameters appear to change concommitantly, and these changes are discussed. [Work supported by NIH.]

The Comparative Performance of an Experimental Hearing Aid and Two Commercial Instruments

An experimental hearing aid, two representative commercial models, and a high fidelity audio-amplification system were explored in a series of systematic articulation tests with hard-of-hearing subjects as listeners. The experimental hearing aid was designed to determine to what extent certain desirable design objectives could be incorporated in a portable hearing aid. A technical description of the experimental instrument is given in an appendix. The paper describes the experimental methods and testing equipment employed and summarizes the results in the form of articulation curves obtained from six hard-of-hearing listeners. The method adequately brings out performance differences in the four instruments and shows the superiority of the experimental hearing aid over the commercial instruments for most subjects.