The interaction of hearing loss and level-dependent hearing protection on speech recognition in noise

Abstract

Objectives: To determine the effects of different control settings of level-dependent hearing protectors on speech recognition performance in interaction with hearing loss. Design: Controlled laboratory experiment with two level-dependent devices (Peltor^® PowerCom Plus? and Nacre QuietPro^®) in two military noises. Study sample: Word recognition scores were collected in protected and unprotected conditions for 45 participants grouped into four hearing profile categories ranging from within normal limits to moderate-to-severe hearing loss. Results: When the level-dependent mode was switched off to simulate conventional hearing protection, there were large differences across hearing profile categories regarding the effects of wearing the devices on speech recognition in noise; participants with normal hearing showed little effect while participants in the most hearing-impaired category showed large decrements in scores compared to unprotected listening. Activating the level-dependent mode of the devices produced large speech recognition benefits over the passive mode at both low and high gain pass-through settings. The category of participants with the most impaired hearing benefitted the most from the level-dependent mode. Conclusions: The findings indicate that level-dependent hearing protection circuitry can provide substantial benefits in speech recognition performance in noise, compared to conventional passive protection, for individuals covering a wide range of hearing losses.     

噪音环境下比较三麦克风与双麦克风助听器对言语分辨率的影响

目的:比较在噪音环境下三麦克风助听器与双麦克风助听器的指向性对成年听力损失患者的言语分辨率提高的影响和效果。 方法:20例双耳感音神经性耳聋患者(女12例,男8例)按听力损失程度分为A、B两组,每组各10人,A组高频平均听力损失(PTA=53.75),B组高频平均听力损失(PTA=73.75)。两组患者双耳配戴实验用两款西门子助听器Triano S(双麦克风指向性模式)和Triano 3(三麦克风指向性模式)耳背机,每款助听器配戴并适应一个月以后,在两个不同的声场中采用言语测试单词予言语分辨率测试,此外结合调查问卷进行评估。 结果:声场评估——两组受试者在不同的声场中测出L50值(50%言语分辨率的信噪比),使用三麦克风指向性模式明显低于双麦克风指向性模式(p<0.01),在较复杂的声场环境中三麦克风指向性的优势体现得更突出,此外,听力损失程度对L50值的影响具显著意义(p<0.01),听力损失越重,L50值越大;问卷评估——绝大多数患者表示三麦克风对解决日常生活当中的听觉困难有显著的效果。结论:噪音环境下三麦克风助听器的指向性能明显提高中度和重度成年感音神经性听力损失患者的言语分辨率。     

The influence of lexical-access ability and vocabulary knowledge on measures of speech recognition in noise

Objective: The main objective was to investigate the effect of linguistic abilities (lexical-access ability and vocabulary size) on different measures of speech-in-noise recognition in normal-hearing listeners with various levels of language proficiency. Design: Speech reception thresholds (SRTs) were measured for sentences in steady-state (SRT_stat) and fluctuating noise (SRT_fluc), and for digit-triplets in steady-state noise (DIN). Lexical-access ability was measured with a lexical-decision test and a word-naming test. Vocabulary size was also measured. For the SRT, keyword scoring and sentence scoring were compared. Study sample: To introduce variation in linguistic abilities, three groups of 24 young normal-hearing listeners were included: higher-educated native, lower-educated native, and higher-educated non-native listeners. Results: Lexical-access ability was most accurately measured with combined results of lexical decision and word naming. Lexical-access ability explained 60% of the variance in SRT. The effect of linguistic abilities on SRTs was up to 5.6 dB for SRT_stat and 8 dB for SRT_fluc. Using keyword scoring reduced this effect by approximately 1.5 dB. For DIN the effect of linguistic ability was less than 1 dB. Conclusions: Lexical-access ability is an important predictor of SRTs in normal-hearing listeners. These results are important to consider in the interpretation of speech-in-noise scores of hearing-impaired listeners.     

Effects of an adaptive filter hearing aid on speech recognition in noise by hearing-impaired subjects

In a digitally controlled adaptive filter, ongoing detection and spectral analysis of quasi steady state noise are performed, and analog filter parameters are adjusted to provide greatest attenuation in frequency regions where noise energy is greatest. Attenuation introduced by the filter affects both speech and noise signals in the attenuation region. Effects of a master hearing aid incorporating an adaptive filter chip were assessed by measuring aided speech recognition threshold in noise with and without the filter. Performance of four hearing-impaired subjects showed that filter effects were related both to the frequency spectrum of the noise and to the distribution of speech information by frequency. No improvement in speech recognition threshold was seen for broadband speech materials in broadband noise. Better performance was observed for low-frequency noise in combination with speech materials for which the important information was confined to high frequencies.     

Assessing speech recognition in noise for listeners with a signal processor hearing aid

Hearing aids with signal processors use advanced circuitry to enhance speech recognition in noise. The effectiveness of these processors has not been well established. The purpose of this study was to evaluate performance on a speech recognition in noise task for listeners wearing a Zeta signal processor aid with the processor turned on and with the processor turned off. In addition, comparisons were made to performance while unaided and aided with a conventional hearing aid. A simple adaptive procedure and a psychometric function were the procedures used. Results for normal-hearing subjects indicate performance was usually better without a hearing aid. Performance when aided was similar for the processor on and the conventional aid. Performance in both of these conditions was clearly better than with the signal processor off. Although results for the hearing-impaired subjects varied widely, there was a trend for better performance with the conventional aid and with the signal processor on than for the signal processor off condition.     

Relationships between speech recognition threshold, average hearing level, and speech importance noise detection threshold.

The aim of this study was to determine (a) if the speech importance noise detection threshold (SINDT) could be used as an accurate estimator of speech recognition threshold (SRT), and (b) whether the SINDT correlates well with various measures of the pure-tone threshold average (PTA). Pure-tone threshold, SRT, and SINDT tests were administered to 94 adults with various degrees of hearing loss. The results demonstrated that SRT can be accurately predicted from SINDT and that these two are highly correlated (r = 0.97). Since a SINDT measurement takes less time than SRT determination, the SINDT test may be recommended as an alternative for SRT in some applications.     

Assessing speech recognition abilities with digits in noise in cochlear implant and hearing aid users

Objective: The primary objective of the study was to investigate the feasibility, reliability, and validity of the Dutch digits in noise (DIN) test for measuring speech recognition in hearing aid and cochlear implant users and compare results to the standard sentences-in-noise (SIN) test. Design: The relation between speech reception thresholds for DIN test and SIN test was analysed to determine the validity of the DIN test. As linguistic skills were expected to make different contributions in these tests, their influence was analysed. Study sample: Participants were 12 normal-hearing listeners, 24 hearing aid users, and 24 cochlear implant users. Results: The DIN test was feasible for more participants than the SIN test. Intraclass correlation coefficients showed high reliability. The standard error of measurement was smaller for the DIN test than for the SIN test. DIN test and SIN test were highly correlated (r = 0.95 and r = 0.56 for NH+ HA and CI users respectively). In the regression analysis no significant contribution of basic linguistic skills or personal factors was found. Conclusion: In the assessment of speech recognition in noise of aided hearing-impaired listeners with hearing aids or cochlear implants, the DIN test is a feasible, reliable and valid test.     

Prediction of speech recognition from audibility in older listeners with hearing loss: effects of age, amplification, and background noise

The extent to which audibility determines speech recognition depends on a number of signal and listener factors. This study focused on three factors: age, background noise modulation, and linear versus wide-dynamic compression amplification. Three audiometrically matched groups of older listeners with hearing loss were tested to determine at what age performance declined relative to that expected on the basis of audibility. Recognition fell below predicted scores by greater amounts as age increased. Scores were higher for steady versus amplitude-modulated noise. Scores for WDRC-amplified speech were slightly lower than for linearly amplified speech across all groups and noise conditions. We found no interaction between age and type of noise. The small reduction in scores for amplitude-modulated compared to steady noise and lack of age interaction suggests that the substantial deficit seen with age in multitalker babble for previous studies was due to some effect not elicited here, such as informational masking.     

Current audiological tests in the diagnosis of sensorineural hearing loss caused by noise

Comprehensive audiological examinations of 69 patients with neurosensory hypoacusis of noise origin have shown that many modern audiological tests fail to discriminate advanced hypoacusis from neurosensory disorders of different nature. In this situation an adequate diagnostic approach is to investigate low voice speech in a noisy environment which may help identify hypoacusis of noise origin that manifests itself in the presence or absence of competing noise.     

Correlational analysis of speech audiometric scores, hearing loss, age, and cognitive abilities in the elderly

A battery of speech audiometric measures and a battery of neuropsychological measures were administered to 200 elderly individuals with varying degrees of pure-tone sensitivity loss. Results were analyzed from the standpoint of the extent to which variation in speech audiometric scores could be predicted by knowledge of pure-tone hearing level, age, and cognitive status. For the four monotic test procedures (PB, SPIN-Low, SPIN-High, and SSI) degree of hearing loss bore the strongest relation to speech recognition score. Cognitive status accounted for little of the variance in any of these four speech audiometric scores. In the case of the single dichotic test procedure (DSI), both degree of hearing loss and speed of mental processing, as measured by the Digit Symbol subtest of the WAIS-R, accounted for significant variance. Finally, age accounted for significant unique variance only in the SSI score.     

The influence of different speech processor and hearing aid settings on speech perception outcomes in electric acoustic stimulation patients

OBJECTIVE: Electric acoustic stimulation (EAS) is an increasingly popular means of treating individuals with a steeply sloping mid-to-high frequency hearing loss, who traditionally do not benefit from hearing instruments. These persons often have too much residual hearing to be considered for a cochlear implant. Several studies have demonstrated the ability both to preserve the remaining low-frequency hearing in these individuals, and to provide significant benefit through combining a cochlear implant with a hearing aid to amplify the same ear. These improvements in performance have been especially noted in noise. Often overlooked is that these outcomes may be influenced by the fitting parameters of both the cochlear implant and the hearing aid. DESIGN: This study assessed four EAS subjects, with a minimum of 1 month's EAS use, on eight different fitting parameters. Sentence testing in different noise levels (+15, +10, and +5 dB SPL) was conducted. Subjects also evaluated each condition using a visual analogue scale. RESULTS: Results demonstrated that a reduced overlap of cochlear implant and hearing aid amplification produced best results across listening conditions. CONCLUSIONS: The hearing aid should be fit to a patient-specific modified audiogram at least up to the point where low-frequency hearing is not measurable. The cochlear implant should be fit from a higher frequency point than is standard in patients without residual hearing in the implanted ear, to provide reduced overlap with the amplification provided by the hearing aid. Therefore, a small amount of overlap between the frequency ranges used by the hearing aid and the cochlear implant seems beneficial.     

Noise-induced hearing loss evolution: influence of age and exposure to noise

The aims of this study were to evaluate the influence of age and exposure to noise in determining the evolution of hearing loss after noise-induced hearing loss has been already established and to define the further evolution of presbycusis. This is a cross-sectional study based on the evaluation of pure-tone audiometry threshold on 568 subjects affected by noise-induced hearing loss and exposed to noise for at least 10 years; noise exposure at testing was 85–90 dB Leqd(A). The further evolution of hearing loss was found to be more related to age than to noise exposure and was significantly less than expected for presbycusis. In conclusion our data support the hypothesis that once NIHL has manifested, it tends to worsen slightly with continued noise exposure and that progressive hearing loss is chiefly due to aging. However, in individuals with NIHL, age-related hearing loss is significantly less at frequencies damaged by noise than in non-noise-exposed individuals.     

Comparisons of speech recognition in noise by mildly-to-moderately hearing-impaired children using hearing aids and FM systems

Four hearing aid arrangements (monaural-omnidirectional, monaural-directional, binaural-omnidirectional, binaural-directional) and a number of FM system-personal hearing aid combinations (including direct input, neck loop, and silhouette inductor--monaural and binaural--and environmental microphone on and off) were evaluated in a school classroom on nine children with mild-to-moderate sensorineural hearing losses. Two measures of speech recognition in noise were employed. First, the signal-to-noise ratio (S/N) yielding 50% identification of spondees was determined using a simple up-down adaptive procedure. Second, word recognition scores were obtained for three amplification arrangements at two different S/Ns (+6 and +15 dB). The average FM advantage over a personal hearing aid was equivalent to a 15-dB improvement in S/N. Activation of the hearing aid microphone caused most of the FM advantage to disappear. The benefit offered by the FM system decreased as the environmental S/N increased but remained significant even at +15 dB. Significant improvement also was found with the use of directional as compared to omnidirectional microphones, both in the hearing aids and FM teacher microphone.     

Effects of reverberation and noise on speech recognition by adults with various amounts of sensorineural hearing impairment

Speech recognition was assessed under three levels of room reverberation, each in quiet and noise, for subjects with varying amounts of sensorineural hearing impairment. The three acoustic environments were: sound suite, reverberant room with a reverberation time (T) = 0.54 s and reverberant room with T = 1.55 s. Three groups of subjects were utilized: normal hearing, mild sensorineural hearing impairment and moderate-to-severe sensorineural hearing impairment. Speech recognition ability for each of the three groups of subjects significantly differed from the other two groups for each of the three reverberant conditions. The detrimental influences of noise and reverberation increased with the magnitude of hearing impairment. In addition, there was an interaction between noise and room reverberation, where the detrimental effects of room reverberation were compounded by the addition of noise.