Fitting hearing aids with the Articulation Index: impact on hearing aid effectiveness

Although most clinical tests focus on how much a particular hearing aid improves speech audibility under controlled conditions, it is unclear how these measures relate to hearing aid effectiveness, or the benefit perceived by the patient under everyday conditions. In this study, the relationship between audibility and hearing aid effectiveness was examined in a cohort of patients who obtained hearing aids through the Veteran's Administration. The measure of audibility was the Articulation Index, a common index of speech audibility. Measures of effectiveness included two hearing-specific surveys and self-reported ratings of global satisfaction and hearing aid use adherence. Results indicated that there were no systematic relationships between measurements of improved audibility and patient ratings of communication ability. Additionally, improved audibility was not related to overall satisfaction with the amplification characteristics of the hearing aid (fitting). However, improved audibility is related to hearing aid use adherence, with patients who achieve better audibility reporting that they use their hearing aids more frequently.     

A test suite for hearing aid evaluation

A test suite has been developed for evaluating hearing aids. The tests in the suite are frequency response, number of processing bands and type of processing, input/output characteristics, processing attack and release times, and broadband distortion. The test suite produces a more complete evaluation of a hearing aid than any previous set of tests, and is suitable for the automatic evaluation of a hearing aid containing unknown processing. The test procedures are described, and sample test results are presented for simulated linear and two-channel compression hearing aids.     

A microprocessor-based acoustic hearing aid for the profoundly impaired listener

We have found that the larynx-frequency pattern of speech presented as a sinusoid can be of greater communicative value to profoundly hearing-impaired people than the complete acoustic signal. The presence of higher harmonics can give poorer labelling of isolated intonation contrasts and often minimal gain in segmental spectrally-based distinctions. These observations have led to the development of a practical, body-worn, pattern-processing hearing aid that uses a microprocessor to sense the (analogue-processed) speech fundamental frequency, transform it into an appropriate amplitude and frequency region, and generate digitally the required output sinusoid. Our findings have important implications for the design of other signal-processing hearing aids in demonstrating that a simplification of speech can lead to enhanced speech receptive abilities in persons with impaired hearing.     

言语测听在助听器选配中的应用

背景:言语测听在助听器的选配中有决定性的作用,但中国临床应用较少。目的:通过言语测听了解耳内式助听器和耳背式助听器的使用者在言语分辨率上的差别。设计:配对对照实验。单位:解放军第四一四医院听力中心,江苏省听力康复中心。对象:选择就诊于解放军第四一四医院听力中心,江苏省听力康复中心耳聋患者62例。32例(耳)使用耳内式助听器耳聋患者中,平均听力损失(500,1000,2000,4000Hz)<85dB,年龄16～60岁。30例(耳)使用耳背式助听器耳聋患者中,平均听力损失(500,1000,2000,4000Hz)<85dB,年龄16-60岁。对实验均知情同意。方法:采用开放法和闭合法,分别对耳内式、耳背式助听器使用者,进行单耳聆听条件下的言语测试。言语信号类型选用单音节词和双音节词,每耳测听单音节词和双音节词各为20个。主要观察指标:耳内式、耳背式助听器对单、双音节词测听比较。结果:耳内式、耳背式助听器使用者的使用效果相比,在言语分辨率上无论开放式、闭合式对双音节词、单音节词的分辨率差异均无显著性意义(P>0.05);双音节词和单音节词的分辨率比较,开放式的状态下,差异有显著性意义(P<0.05);闭合式的状态下,差异无显著性意义(P>0.05)。结论:在助听器选配中言语测听的实际实施受诸多因素影响。     

Two-state compression of spectral tilt: individual differences and psychoacoustical limitations to the benefit from compression

A psychoacoustic rationale was developed for a hearing aid design in which compression of spectral tilt was incorporated without any instantaneous nonlinear distortion. This involved switching between a 'flat' and a 'rising' frequency response; the switching was done slowly to avoid audible transients and was controlled by feedback derived from comparison of output levels in low- and high-frequency channels, approximating voiced/unvoiced detection. The effect of this switching process was to narrow the distribution of spectral tilt values compared with the input. Asynchrony between the switching and the triggering speech structures was avoided by also delaying the signal path. Unfortunately, hearing-impaired listeners performed more poorly on the switching system than on either of the control 'flat' or 'rising' frequency-responses. An explanation is offered (on the basis of growing evidence from perceptual experiments) of the perceptual importance of temporal envelope contours within individual frequency bands. It was possible, in part, to predict individuals' results in the switching condition from age and audiometric or psychoacoustic characteristics. The results suggest a modification to the switching design, and they point to an intrinsic limit to the ability of all hearing aids of the compression type to enhance intelligibility.     

An audiological profile of elderly Australians reporting speech affecting stroke

This study examined the audiological profile and hearing rehabilitation of 73 people who reported having had speech-affecting strokes. Participants were drawn from the Blue Mountains Hearing Study (BMHS), a population survey of age-related hearing loss in 2956 members of a representative elderly Australian community. While speech-affecting stroke did not seem to cause greater levels of hearing impairment or handicap than for other participants matched for age and gender, this may be due to a low prevalence of participants with severe effects on speech or language as a result of their stroke. Although 52% of participants self-reported a hearing loss, fewer than 23% had ever worn a hearing aid with only 15% wearing hearing aids for more than 1 hour per day. Pure tone audiometry identified 64% of participants with thresholds considered appropriate for hearing aid fitting when previously established criteria were applied. Questions concerning use of hearing aid/s and self reported hearing loss were not reliable in determining which participants with a speech affecting stroke met these audiometric criteria. The risks of uncorrected hearing loss compromising speech and language assessment and rehabilitation following stroke are discussed.     

Physiological assessment of contrast-enhancing frequency shaping and multiband compression in hearing aids

Spectral enhancement is now being used in many hearing aids in an attempt to compensate for broadened cochlear filtering. However, spectral enhancement may be counteracted by multiband-compression algorithms designed to compensate for the reduced dynamic range of the impaired cochlea. An alternative scheme for spectral enhancement, contrast-enhancing frequency shaping (CEFS), has been proposed, which results in an improved neural representation of the first and second formants of voiced speech segments in the impaired ear. In this paper, models of the normal and impaired ear are used to assess the compatibility of CEFS with multiband compression. Model auditory nerve responses were assessed under four conditions: (1) unmodified speech presented to a normal ear; (2) amplified, unshaped speech presented to an impaired ear; (3) CEFS speech presented to an impaired ear; and (4) CEFS+multiband-compression speech presented to an impaired ear. The results show that multiband compression does not reduce the benefits of CEFS, and in some cases multiband compression assists in preventing distortion of the neural representation of formants. These results indicate that the combination of contrast-enhancing frequency shaping and multiband compression should lead to improved perception of voiced speech segments in hearing aid users.     

听障儿童听觉言语能力影响因素的研究

目的探讨影响听障儿童听觉言语能力的相关因素.方法对43名听障儿童的助听听阈、听觉能力、言语能力以及学习能力等方面进行测查.结果性别、助听方式对听障儿童的听觉言语能力无显著性影响(P>0.05);助听听阈对听障儿童的听觉能力有显著性影响(P<0.05);语言能力与学习能力呈显著正相关(P<0.05);听觉能力对言语能力有非常显著性正向预测作用(P<0.001).结论及时、有效地给予听觉补偿,抓住语言发展的关键期,尽早进行康复训练,有助于听障儿童听觉言语能力的康复.     

全数字和模拟助听器听力补偿效果的对比研究

目的：比较三种峰力大功率助听器在重度以上听力障碍患者言语康复中对声音的感知、辨别和主观感觉的影响。方法：以助听听阈、Ling‘s 6音分辨率、患者的主观感觉为指标比较三种助听器在声音的感知、辨别、舒适程度方面的差别。结果：411、412较PPC-2在5个频率的助听听闻均有显著降低。411助听与PPC-2助听时元音的分辨率比较差异无显著性意义；而辅音分辨率有显著改善。PPC-2助听与412助听时的分辨率比较只有[u]差异无显著性意义，其余5音412助听时的分辨率有显著提高。而411与412助听状态下Ling‘s 6音分辨率差异尤显著性意义。主观评价：患者感觉411、412较PPC-2好。结论：大功率数字助听器峰力411、412对于重度听力损失以上的患者较传统助听器PPC-2有更好的助听效果。     

Speech discrimination with an 8-channel compression hearing aid and conventional aids in background of speech-band noise

The design for a multichannel compression hearing aid was developed from previous experimental and theoretical work in our laboratory concerning pitch perception in normal-hearing subjects. The new hearing aid, implemented with off-line digital signal processing, was tested on twenty subjects with sensorineural hearing loss using speech sounds in a background of speech-spectrum noise. Five signal-to-noise ratios (+15 to -5dB) were used at two noise levels (60 and 70 dB SPL). Hearing-loss subjects listened to these stimuli under three different conditions: a) processed by the new multichannel compression hearing aid; b) processed by a conventional hearing aid; and c) unprocessed. The performance of normal-hearing subjects with the unprocessed stimuli provided another condition against which the performance in the two hearing aid conditions could be evaluated. Both aided conditions provided improved performance over the unprocessed condition and the multichannel compression aid produced better performance than the conventional aid. In the case of 4 of the 20 subjects, with less severe gradually sloping hearing losses, the new multichannel compression aid produced near-normal performance even at low signal-to-noise ratios. Some aspects of the results also suggested that learning to use the aid was more important in the case of the multichannel compression aid than in the case of the conventional aid. These results indicate that a multichannel compression hearing aid can be very effective in some individuals with sensorineural hearing loss and is superior to a conventional hearing aid in most subjects.     

Evaluation of adaptive multimicrophone algorithms for hearing aids

It appears that one of the most important factors limiting the usefulness of hearing aids is the high sensitivity of hearing aid users to interfering sounds. In this work, the possibility of utilizing computing power that could be packaged into a unit the size of a hearing aid in order to cancel out noises before they reach the ear was investigated. Algorithms for combining the outputs of a number of microphones so as to achieve a considerable noise reduction are proposed and evaluated, and some questions related to implementation are studied. Some experimental results based on numerical and listening tests are presented. The computation is started by indicating to the system a silent period of the main speaker. In order to minimize distortion for the main speaker, the algorithms try to produce an output that matches the first few autocorrelations of the main speaker. It is expected that the system should be able to track sufficiently slow variations in the positions of the noise sources and the main speaker.     

Design and evaluation of a two-channel compression hearing aid

The design of a two-channel compression hearing aid for persons with moderate sensorineural hearing losses with recruitment is described. The aid applies slow-acting automatic gain control (AGC) to the whole signal, and then splits the signal into two bands, with separate fast-acting (syllabic) AGC in each band. Trials evaluating the aid have shown that it allows speech in quiet to be understood over a wide range of sound levels without any need to adjust the controls on the aid. It also gives speech intelligibility in noise superior to that allowed by a comparable linear (non-compression) aid, a comparable single-channel compression aid, and by unaided listening. Pilot experiments comparing two different methods for fitting the aid suggest that fitting using speech as the test signal is superior to fitting using narrow band tonal signals.     

A time-domain digital simulation of hearing aid response

A time-domain digital simulation of an in-the-ear (ITE) hearing aid has been developed. The stimulation allows modeling of nonlinear effects such as compression and amplifier distortion in addition to linear processing and acoustics. The simulation includes a microphone, two-channel compression processing, an amplifier with clipping distortion, a receiver, an ear canal and ear drum, and feedback and direct sound transmission through the vent. Simulation results for a linear hearing aid are similar to those obtained for frequency-domain representations of the analog system. Examples of responses for nonlinear systems are also provided.     

40Hz听觉相关电位结合听性脑干反应在婴幼儿助听器验配中的应用

目的：为双耳感音神经性聋的婴幼儿及小龄儿童客观验配助听器。方法：采用40Hz听觉相关电位(AERP)结合听性脑干反应(ABR)来客观评估聋儿听力，获得等效于成人的纯音听阈曲线并用于助听器验配。结果：36例中有32例配戴助听器半年后验证聋儿的行为听阈均进入“言语香蕉图”，聆听行为较验配前有改善。结论：ABR及40HzAERP可用于婴幼儿和小龄儿童助听器的客观验配，为他们尽快进入正常听觉康复训练赢得宝贵时间。     

New developments in hearing aid technology

The last decade has seen numerous and significant improvements in hearing aid technology. Digital hearing aids are becoming increasingly common and have already replaced a considerable portion of the hearing aids using the older analogue technology. Efficient noise reduction methods, most notably multi-microphone systems for hearing aids, can increase speech intelligibility in adverse listening situations and noisy environments. Accessories, such as e.g. wireless classroom communication systems (FM systems) and remote controls are becoming smaller and less visible. As a consequence of the increased complexity of modern hearing aids, however, hearing aid fitting has become considerably more complex.     

Auditory filtering and the discrimination of spectral shapes by normal and hearing-impaired subjects

A review of the literature suggests that many hearing-impaired patients suffer from sensory deficits in addition to the reduced audibility of speech signals. Poor frequency resolution, or abnormal spread of masking, is a consistently identified deficit in sensorineural hearing loss. Frequency resolution was measured in individual subjects using the input filter pattern paradigm, and the minimum detectable amplitude of a second-formant spectral peak in a spectral-shape discrimination task was also determined for each subject. The two tasks were designed to test the identical frequency regions in each subject. A nearly perfect correlation was found between the degree of frequency resolution as measured by the input filter pattern and performance on the spectral-shape discrimination task. These results suggest that measures of frequency selectivity may offer predictive value as to the degree of impairment that individual hearing-impaired patients may have in perceiving the spectral characteristics of speech, and also lead to suggestions for signal processing strategies to aid these patients.     

Effectiveness of an affordable hearing aid with elderly persons

Purpose. This study evaluated the effectiveness of a recently developed, low-cost 'over-the-counter' style hearing aid with elderly people, who had mild to moderate mixed or sensorineural hearing losses. Two aspects were focused upon, objective change in the participants' aided hearing measures and the self-reported performance and benefit obtained from the hearing aid.

Method. The hearing aids were trialed by 19 elderly persons over a 3-month period. Aided hearing thresholds and real-ear insertion gain measures were obtained from participants, three questionnaires (the Client-Oriented Scale of Improvement [COSI], the International Outcome Inventory for Hearing Aids [IOI-HA] and the Profile of Hearing Aid Performance - Chinese version [PHAP-C]) were completed, and an open-ended interview was conducted.

Results. Objective tests noted that the trial hearing aid was able to provide appropriate amplification for the elderly participants in this study. The device was rated by the majority of participants as providing benefit, with 16 of the participants (84%) using their hearing aid from at least 1 to over 8 h each day and with all participants considering the low-cost instrument 'worth the trouble' of wearing. Participant ratings of benefit with the IOI-HA were comparable with those obtained in a normative study in which subjects used more expensive conventional hearing aids. Using the COSI questionnaire, participants typically concluded that their hearing improvement with the study device was 'slightly better' to 'better' than without amplification. The PHAP-C questionnaire results indicated that, while wearing their hearing aids, participants experienced difficulties only infrequently in most everyday listening situations. Comments made during open-ended interviews were equally positive and negative, with most negative comments focused on difficulties with either acoustic feedback or background noise annoyance while wearing the hearing instrument.

Conclusion. Affordable, over-the-counter hearing devices provide a potential opportunity for greater numbers of persons with hearing loss to access amplification and benefit from improved communicative abilities. Further investigation and further development of these instruments is warranted, to provide enhanced rehabilitation outcomes for elderly persons with hearing impairment.     

言语测听在助听器选配中的应用

目的言语测听在助听器的选配中有决定性的作用,中国临床应用较少,通过言语测听了解耳内式助听器和耳背式助听器的使用者在言语分辨率的差别。方法采用开放法和闭合法,分别对耳内式、耳背式助听器使用者,进行单耳聆听条件下的言语测试。言语信号类型选用单音节词和双音节词,每耳测听单音节词和双音节词各为20个。结果耳内式、耳背式助听器使用者的使用效果相比,在言语分辨率上无论开放式、闭合式对双音节词、单音节词的分辨率无显著性差异(P>0.05);双音节词和单音节词的分辨率比较,开放式的状态下,有显著性差异(P<0.05);闭合式的状态下,无显著差异(P>0.05)。结论在助听器的选配中言语测听的实际实施受诸多因素的影响。     

Effectiveness of an affordable hearing aid with elderly persons

Purpose.?This study evaluated the effectiveness of a recently developed, low-cost ‘over-the-counter’ style hearing aid with elderly people, who had mild to moderate mixed or sensorineural hearing losses. Two aspects were focused upon, objective change in the participants' aided hearing measures and the self-reported performance and benefit obtained from the hearing aid.

Method.?The hearing aids were trialed by 19 elderly persons over a 3-month period. Aided hearing thresholds and real-ear insertion gain measures were obtained from participants, three questionnaires (the Client-Oriented Scale of Improvement [COSI], the International Outcome Inventory for Hearing Aids [IOI-HA] and the Profile of Hearing Aid Performance – Chinese version [PHAP-C]) were completed, and an open-ended interview was conducted.

Results.?Objective tests noted that the trial hearing aid was able to provide appropriate amplification for the elderly participants in this study. The device was rated by the majority of participants as providing benefit, with 16 of the participants (84%) using their hearing aid from at least 1 to over 8?h each day and with all participants considering the low-cost instrument ‘worth the trouble’ of wearing. Participant ratings of benefit with the IOI-HA were comparable with those obtained in a normative study in which subjects used more expensive conventional hearing aids. Using the COSI questionnaire, participants typically concluded that their hearing improvement with the study device was ‘slightly better’ to ‘better’ than without amplification. The PHAP-C questionnaire results indicated that, while wearing their hearing aids, participants experienced difficulties only infrequently in most everyday listening situations. Comments made during open-ended interviews were equally positive and negative, with most negative comments focused on difficulties with either acoustic feedback or background noise annoyance while wearing the hearing instrument.

Conclusion.?Affordable, over-the-counter hearing devices provide a potential opportunity for greater numbers of persons with hearing loss to access amplification and benefit from improved communicative abilities. Further investigation and further development of these instruments is warranted, to provide enhanced rehabilitation outcomes for elderly persons with hearing impairment.     

91 例成人听力状况及助听效果分析

目的了解成人听力状况,评价助听效果。方法回顾性分析91 例听力损害成人纯音测听法双耳气骨导听阈及助听听阈;通过与患者的日常用语交谈确定患者满意程度。结果裸耳听阈与助听听阈呈正相关;助听效果最适并不代表患者心理感知最好;听力剥夺时间越短,佩戴助听器后的心理感知越好;听力曲线呈平坦型、上升型、缓降型的助听效果较佳,蜀型助听效果较差。结论应加强耳科初级保护,及时发现听力问题,同时保证助听器发挥最大作用。