噪声环境下自适应方向性与全向性麦克风助听模式对言语分辨率的影响

目的比较噪声环境下自适应方向性麦克风与全向性麦克风助听模式对听力损失患者言语识别率的影响。方法 20例双耳对称性感音神经性听力损失患者(男9例,女11例)均单耳佩戴助听器(Resound Canta 780-D),佩戴并适应6个月以上,随机分为两组,每组10例,A组先将助听器麦克风模式切换至全向性,适应2周后测试其在噪声环境下的言语识别率,并完成助听器效果评估表(the abbreviated profile of hearing aid benefit,APHAB)及麦克风效果问卷(microphone performance questionnaire,MPQ);再将麦克风模式切换至自适应方向性,适应2周后重复以上测试。B组麦克风模式切换顺序先为自适应方向性,再为全向性,测试方法同A组。结果声场评估示,噪声环境下,患者使用自适应方向性麦克风助听模式的言语识别率(73.20%±20.69%)高于全向性麦克风模式(64.00%±18.76%),差异有显著统计学意义(P<0.001)。APHAB评估结果显示在有背景噪声、回声、厌恶声存在的环境下,受试者使用自适应方向性麦克风助听模式能更好地提高言语交流能力。MPQ问卷表评估结果显示,除第六类场景(信号来源于听者正前方、无噪声、低混响)外,受试者在其余九类交流场景时使用自适应方向性麦克风助听模式的言语识别率均优于全向性模式。结论噪声环境下自适应方向性麦克风助听模式可显著提高患者的言语识别率。     

单通道与多通道自适应方向性麦克风助听器对正常成年人噪声下言语识别率的影响

目的 比较噪声环境下单通道和多通道自适应麦克风助听器的指向性对正常成年人言语识别率的影响.方法 30例(60耳)正常青年人(男、女各15例)分别双耳配戴Diva 9(单通道自适应麦克风指向性模式)和Inteo 9(多通道自适应麦克风指向性模式)耳背机,在不同信噪比的动态噪声漫射声场中进行言语识别率测试,对助听效果进行评估.结果 单通道自适应方向性麦克风(Diva9)及多通道自适应方向性麦克风(Inteo9)L50值[达到50%言语识别率所需的信噪比(dB)]分别为0.63和-4.63 dB,两者比较差异有显著统计学意义(P＜0.001).结论 自适应方向性麦克风系统的多通道极性最优化模式可显著提高配戴者的言语识别能力.     

频率特异性三指向性麦克风在助听器中的应用

目的比较双耳佩戴助听器时自动同步调节音量和手动分别调节音量在声源定位方面的区别以及不同噪声环境下频率特异性三麦克风和全通道三麦克风自适应指向性对言语分辨率的影响。方法40例感音神经性聋患者,均为双侧中度到重度高频下降型感音神经性听力损失,随机分为A、B两组,每组各20人,A组平均听力损失(1、24、kHz)为67.1 dB,B组平均听力损失为69.5 dB。两组患者双耳佩戴实验用两款西门子助听器ACURISP(自适应指向性模式)(A组)和Triano 3 P(自适应指向性模式)(B组)耳背机,在佩戴助听器前和3个月后分别在同一声场进行佩戴前后声源定位测试,以及单个移动噪声和多重噪声环境下言语分辨率测试,记录达到50%言语分辨率时的信噪比,即L50,并结合问卷调查对无线技术在日常生活中的便利性进行评估。结果声场评估:两组受试者在配戴助听器3个月后声源定位能力有明显差异,使用频率特异性三麦克风自适应指向性模式者复合噪声源声场中测出L50值,明显低于使用三麦克风自适应指向性模式者(P<0.01);问卷评估:绝大多数患者表示无线技术给日常助听器调节带来了很大的便利。结论自动同步音量调节对保持助听后声源定位能力作用明显,在多噪声环境下频率特异性三麦克风助听器的自适应指向性能明显提高重度成年感音神经性听力损失患者的言语分辨率,并且无线技术提高了日常调节助听器的便利性。     

方向性麦克风对语后聋人工耳蜗使用者言语识别能力的影响

目的 探讨方向性麦克风系统对人工耳蜗使用者言语识别能力的影响，以期为解决人工耳蜗使用者噪声下言语识别困难提供参考。方法 采用普通话噪声下言语识别测试以及自行编制的聆听感受自评问卷，对14例母语为汉语普通话的成人语后聋人工耳蜗植入者进行不同麦克风系统和拾音模式下的单音节词分辨能力、短句识别能力以及聆听感受评估，采用SPSS 26.0统计软件对结果进行统计分析。结果 (1)言语识别能力：麦克风拾音模式对人工耳蜗使用者噪声条件下言语识别率得分有显著影响，SONNET/自适应模式得分最高，SONNET/全向模式、SONNET/定向模式和OPUS/全向模式的得分相当；麦克风拾音模式对人工耳蜗使用者安静条件下言语识别率得分无显著影响：SONNET/全向模式与OPUS/全向模式得分相当。(2)聆听感受自评：麦克风拾音模式对人工耳蜗使用者噪声条件下问卷得分有显著影响，SONNET/自适应模式得分最高，SONNET/定向模式得分次之，SONNET/全向模式和OPUS/全向模式的得分相当。麦克风拾音模式对人工耳蜗使用者安静条件下问卷得分无显著差异，SONNET/定向模式与OPUS/全向模式得分相当。(3)...     

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。     

语前聋患儿一侧人工耳蜗植入对侧佩戴助听器聆听效果分析

目的：分析语前聋患儿一侧人工耳蜗植入（cochlear implant ,CI）对侧佩戴助听器模式下的聆听效果,以及非植入耳残余听力对聆听效果的影响。方法选取一侧人工耳蜗植入对侧佩戴助听器的语前聋患儿18例,分别测试其在单侧人工耳蜗植入、一侧人工耳蜗植入对侧佩戴助听器的双耳聆听模式（ bimodal fitting ,BIM ）安静环境及稳态噪声环境下标准中文短句、双音节词、单音节词的识别率。结果安静状态下本组患儿CI、BIM 模式单音节词言语识别率分别为82．67％±12．23％、83．61％±12．22％,双音节词分别为76．00％±16．13％、78．11％±14．84％,标准中文短句分别为60．11％±17．18％、65．43％±16．76％;信噪比10 dB环境下CI、BIM 助听模式患儿单音节词识别率分别为75．50％±14．12％、76．83％±14．15％,双音节词分别为68．22％±17．15％、77．18％±16．83％,标准中文短句分别为49．39％±19．26％、56．33％±19．55％,除两种模式下单音节词外其余言语识别率差异均有统计学意义（P＜0．05）,且非植入耳250、500 Hz助听听阈与BIM 模式言语识别率呈负相关。结论语前聋患儿双耳双模式聆听时有一定优势,这种优势可能主要来自低频残余听力。     

噪声对低龄正常儿童言语感知的影响

目的探讨言语谱噪声(speech spectrum-shaped noise,SSN)和多人谈话噪声(babble noise,BN)对低龄正常儿童普通话词汇相邻性测试(Mandarin lexical neighborhood test,MLNT)言语感知的影响。方法 34例3~6岁正常听力儿童分为SSN组(21例)和BN组(13例),使用噪声下普通话词汇相邻性测试系统对两组儿童行声场下的言语测试,以听说复述方法获得不同信噪比下的言语识别率,比较两组两类噪声下的单音节易词表、难词表和双音节易词表、难词表的识别率-信噪比函数曲线(P-SNR曲线)和言语识别阈(SNR50)。结果 SSN组双音节易词表和难词表的SNR50阈值分别为-3dB、-0.5dB,单音节易词表和难词表的SNR50分别为-1dB、3.5dB;BN组双音节易词表和难词表的SNR50分别为-3dB、2dB,单音节易词表和难词表的SNR50分别为0.5dB、10dB。两组除双音节易词表SNR50相同外,其余各类词表BN组的SNR50均比SSN组高。词汇学因素对正常听力儿童噪声下的开放式言语识别的影响仍表现出易词识别率高于难词,双音节词识别率高于单音节词。结论对3~6岁正常听力儿童BN的掩蔽效应比SSN强,词汇学因素在噪声下仍然影响儿童的言语识别。     

听神经病患者噪声下言语测听临床应用与分析

目的对比听神经病患者安静与噪声下言语识别率的差异并与正常受试者、感音神经性听力损失组、听神经瘤组进行比较。方法测试在符合国家标准的隔声室内进行,纯音测试及言语测试应用校准后丹麦耳听美Conera听力计Otosuite(版本号4.82)联结计算机输出言语声,受试者佩戴头戴式耳机TDH-39、B71骨导振动器测试纯音。言语识别测试材料采用解放军总医院郗昕编制的《普通话言语测听—单音节识别测试》词表,在安静和噪声环境下,分别测试听神经病患者10例、感音神经性聋患者11例、听神经瘤患者11例和听力正常受试者10例患者在平均听阈、阈上10dB、20dB、30dB处的言语识别率以及信噪比为-0、-5、-10、-15dB的言语识别率得分。结果听神经病患者在噪声下言语识别能力明显低于听神经瘤组、感音神经性听力损失组以及正常听力组(P<0.05);具有相似听力阈值及听力曲线的AN患者,给予安静及不同噪声强度测试,可呈现较差及较好二级分化的SRS曲线;正常组在信噪比为-0、-5、-10、-15dB的环境下,信噪比为10dB时对比自身安静环境言语识别得分无显著性差异(P>0.05),而听神经病组、听神经瘤组和感音神经性听力损失组在-10 SNR处均有显著性差异(P<0.05)。听神经病患者在安静环境下随刺激声强度的升高会出现"回跌"现象。听神经病患者总体水平在安静与噪声环境下纯音听阈与言语识别得分均与无相关性(R2=0.07),其他三组呈现负的弱相关或强相关。结论安静环境下言语识别能力较好的听神经病患者在噪声环境中下降程度更为显著,相对于安静环境言语识别测试更加敏感;采用平均阈上30dB及-10dB信噪比测试,所得言语识别得分可作为临床评价言语功能的敏感指标,且对于听神经病诊断和病变定位及程度分析更具有现实意义,能够更全面评估听神经病患者的言语交流能力。     

极重度感音神经性聋佩戴助听器与人工耳蜗植入患儿残余听力的比较分析

目的:通过回顾性比较分析极重度感音神经性聋患儿接受佩戴助听器和人工耳蜗植入手术2种不同干预方式人群的听力学评估参数,探讨极重度感音神经性聋患儿有效残余听力的临床判断方法.方法:选取听力学评估和言语康复训练资料完整的22例双耳极重度感音神经性聋患儿,其中10例佩戴助听器并接受超过3个月的言语康复训练,另外12例接受人工耳蜗植入手术,其中有10例年龄区间与佩戴助听器组一致.佩戴助听器组患儿,根据言语康复训练效果分为良好(7例)和较差(3例),分别统计其佩戴助听器前ASSR和听力言语康复训练期间裸耳纯音测听在500、1000、2000、4000 Hz 4个频点的听阈阈值情况.年龄与佩戴助听器组一致的10例接受人工耳蜗植入术患儿,根据术前有否佩戴助听器情况,分为曾佩戴助听器但听力言语康复效果差者(5例)和未接受佩戴助听器者(5例),分别统计其佩戴助听器前和(或)手术前的ASSR在500、1000、2000、4000 Hz 4个频点的听阈阈值情况.结果:①ASSR的阈值情况.佩戴助听器且言语康复训练效果良好的7例(14耳)患儿,平均每耳有2.71个频点可引出ASSR反应,所引出的ASSR平均阈值为(110.92±7.43 )dB HL;佩戴助听器言语康复训练效果较差的3例患儿,再加上曾佩戴助听器但听力言语康复效果差而接受人工耳蜗植入术的5例,共8例(16耳),平均每耳只有1.06个频点可引出ASSR反应,所引出的ASSR平均阈值为(110.88±8.52 )dB HL.②裸耳纯音测听情况.佩戴助听器且言语康复训练效果良好的7例(14耳)患儿,所测频点的平均听阈为(96.11±7.81) dB HL;其中,每耳平均有3个频率点的裸耳纯音测听阈值≤100 dB HL.而在效果差的3例(6耳)患儿中,所测频点的平均听阈为(112.19±5.15) dB HL,裸耳纯音测听阈值≤100 dB HL耳的数量为0.结论:500、1000、2000、4000 Hz 各频率引出ASSR的频点数量和裸耳纯音测听阈值≤100 dB HL的数量,是临床上判断极重度感音神经性聋患儿有否存在可利用助听残余听力的有效指标.     

方向性麦克风技术在助听器中的应用

引言 目前，助听器的广泛使用已经使广大听力损失患者在很大程度上改善了他们的生活质量，但这些助听器用户在日常生活中还是会有一些聆听上的困难，尤其是在噪声环境下与人交谈。方向性麦克风系统（directional microphones system）也译为指向性麦克风，是用于提高助听器言语信噪比的一项重要技术，尤其能改善在噪声环境下的言语清晰度（可懂度）。本文通过介绍方向性麦克风的原理、作用以及实际应用方面等相关知识来帮助听力从业人员、技术人员和用户更好地了解和使用这项技术。     

Noise reduction results of an adaptive filtering technique for dual-microphone behind-the-ear hearing aids

OBJECTIVE: The performance of an adaptive beam-former in a 2-microphone, behind-the-ear hearing aid for speech understanding in noisy environments was evaluated. Physical and perceptual evaluations were carried out. This was the first large-scale test of a wearable real-time implementation of this algorithm. The main perceptual research questions of this study were related to the influence on the noise reduction performance of (1) the spectro-temporal character of the jammer sound, (2) the jammer sound scene, (3) hearing impairment, and (4) the basic microphone configuration in the hearing aid. Four different speech materials were used for the perceptual evaluations. All tests were carried out in an acoustical environment comparable to living room reverberation. DESIGN: The adaptive beamformer was implemented in Audallion, a small, body-worn processor, linked to a Danasound 2-microphone behind-the-ear aid. The strategy was evaluated physically in different acoustical environments. Using speech reception threshold (SRT) measurements, the processing was evaluated perceptually and the different research questions addressed with three groups of subjects. Groups I, II, and III consisted of 10 normal-hearing, 5 hearing-impaired, and 7 normal-hearing persons, respectively. The tests were carried out in three spectro-temporally different jammer sounds (unmodulated and modulated speech weighted noise, multitalker babble) and in three different noise scenarios (single noise source at 90 degrees, noise sources at 90 degrees and 270 degrees relative to speaker position, diffuse noise scene). Two microphone configurations were compared: a device equipped with two omnidirectional microphones and a device equipped with one hardware directional and one omnidirectional microphone. In each of these conditions, the adaptive beamformer and the directional and omnidirectional microphone configurations were tested. RESULTS: The improvement in signal-to-noise ratio from the use of the adaptive beamformer did not depend on the spectro-temporal character of the jammer sounds and the speech materials used, although the absolute levels of the SRTs varied appreciably for different speech-noise combinations. The performance of the adaptive noise reduction depended on the jammer sound scene. CONCLUSIONS: No difference in signal-to-noise ratio improvement was observed between hearing-impaired and normal-hearing listeners, although individual SRT levels may differ. On average, an SRT improvement of 7.7 and 3.9 dB for a single noise source at 90 degrees and 5.9 and 3.4 dB for two noise sources at 90 degrees and 270 degrees was obtained for both normal-hearing and hearing-impaired listeners, using the adaptive beamformer and the directional microphone, respectively, relative to the omnidirectional microphone signal. In diffuse noise, only small improvements were obtained.     

Better speech perception in noise with an assistive multimicrophone array for hearing AIDS

OBJECTIVE: To evaluate the improvement in speech intelligibility in noise obtained with an assistive real-time fixed endfire array of bidirectional microphones in comparison with an omnidirectional hearing aid microphone in a realistic environment. DESIGN: The microphone array was evaluated physically in anechoic and reverberant conditions. Perceptual tests of speech intelligibility in noise were carried out in a reverberant room, with two types of noise and six different noise scenarios with single and multiple noise sources. Ten normal-hearing subjects and 10 hearing aid users participated. The speech reception threshold for sentences was measured in each test setting for the omnidirectional microphone of the hearing aid and for the hearing aid in combination with the array with one and three active microphones. In addition, the extra improvement of five active array microphones, relative to three, was determined in another group of 10 normal-hearing listeners. RESULTS: Improvements in speech intelligibility in noise obtained with the array relative to an omnidirectional microphone depend on noise scenario and subject group. Improvements up to 12 dB for normal-hearing and 9 dB for hearing-impaired listeners were obtained with three active array microphones relative to an omnidirectional microphone for one noise source at 90 degrees . For three uncorrelated noise sources at 90 degrees, 180 degrees, and 270 degrees, improvements of approximately 9 dB and 6 dB were obtained for normal-hearing and hearing-impaired listeners, respectively. Even with a single noise source at 45 degrees, benefits of 4 dB were achieved in both subject groups. Five active microphones in the array can provide an additional improvement at 45 degrees of approximately 1 dB, relative to the three-microphone configuration for normal-hearing listeners. CONCLUSIONS: These improvements in signal-to-noise ratio can be of great benefit for hearing aid users, who have difficulties with speech understanding in noisy environments.     

Speech intelligibility in noisy environments with one- and two-microphone hearing aids

In this study speech intelligibility in background noise was evaluated with 10 binaural hearing-aid users for hearing aids with one omnidirectional microphone and a hearing aid with a two-microphone configuration (enabling an omnidirectional as well as a directional mode). Signal-to-noise ratio (SNR) measurements were carried out for three different types of background noise (speech-weighted noise, traffic noise and restaurant noise) and two kinds of speech material (bisyllabic word lists and sentences). The average SNR improvement of the directional microphone configuration relative to the omnidirectional one was 3.4 dB for noise presented from 90 degrees azimuth. This improvement was independent of the specific type of noise and speech material, indicating that one speech-in-noise condition may yield enough relevant information in the evaluation of directional microphones and speech understanding in noise.     

Speech-clarity judgments of hearing-aid-processed speech in noise: Differing polar patterns and acoustic environments

This investigation assessed the extent to which listeners’ preferences for hearing aid microphone polar patterns vary across listening environments, and whether normal-hearing and inexperienced and experienced hearing-impaired listeners differ in such preferences. Paired-comparison judgments of speech clarity (i.e. subjective speech intelligibility) were made monaurally for recordings of speech in noise processed by a commercially available hearing aid programmed with an omnidirectional and two directional polar patterns (cardioid and hypercardioid). Testing environments included a sound-treated room, a living room, and a classroom. Polar-pattern preferences were highly reliable and agreed closely across all three groups of listeners. All groups preferred listening in the sound-treated room over listening in the living room, and preferred listening in the living room over listening in the classroom. Each group preferred the directional patterns to the omnidirectional pattern in all room conditions. We observed no differences in preference judgments between the two directional patterns or between hearing-impaired listeners’ extent of amplification experience. Overall, findings indicate that listeners perceived qualitative benefits from microphones having directional polar patterns.     

Using hearing aid adaptive directional microphones to enhance cochlear implant performance

The goal of this study was to investigate whether adaptive microphone directionality could enhance cochlear implant performance. Speech stimuli were created by fitting a digital hearing aid with programmable omnidirectional (OM), fixed directional (FDM), or adaptive directional (ADM) microphones to KEMAR, and recording the hearing aid output in three noise conditions. The first condition simulated a diffused field with noise sources from five stationary locations, whereas the second and third condition represented one or three non-stationary locations in the back hemifield of KEMAR. Speech was always presented to 0° azimuth and the overall signal-to-noise ratio (SNR) was +5 dB in the sound field. Eighteen postlingually deafened cochlear implant users listened to the recorded test materials via the direct audio input of their speech processors. Their speech recognition ability and overall sound quality preferences were assessed and the correlation between the amount of noise reduction and the improvement in speech recognition were calculated. The results indicated that ADM yielded significantly better speech recognition scores and overall sound quality preference than FDM and OM in all three noise conditions and the improvement in speech recognition scores was highly correlated with the amount of noise reduction. Factors influencing the noise level are discussed.     

Quantification of directional benefit across different polar response patterns

The purpose of this study was to assess the relationship between the directivity of a directional microphone hearing aid and listener performance. Hearing aids were fit bilaterally to 19 subjects with sensorineural hearing loss, and five microphone conditions were assessed: omnidirectional, cardioid, hypercardioid, supercardioid, and "monofit," wherein the left hearing aid was set to omnidirectional and the right hearing aid to hypercardioid. Speech perception performance was assessed using the Hearing in Noise Test (HINT) and the Connected Speech Test (CST). Subjects also assessed eight domains of sound quality for three stimuli (speech in quiet, speech in noise, and music). A diffuse soundfield system composed of eight loudspeakers forming the corners of a cube was used to output the background noise for the speech perception tasks and the three stimuli used for sound quality judgments. Results indicated that there were no significant differences in the HINT or CST performance, or sound quality judgments, across the four directional microphone conditions when tested in a diffuse field. Of particular interest was the monofit condition: Performance on speech perception tests was the same whether one or two directional microphones were used.     

Investigating Speech Recognition and listening effort with different device configurations in adult cochlear implant users

Objectives: The purpose of this study was to investigate speech recognition in noise and listening effort among a group of adults with cochlear implants (CIs). Two main research questions were addressed. First, what are the effects of omni versus directional microphone configuration on speech recognition and listening effort for noisy conditions? Second, what is the effect of unilateral versus bimodal or bilateral CI listening on speech recognition and listening effort in noisy conditions?

Design: Sixteen adults (mean age 58 years) with CIs participated. Listening effort was measured using a dual-task paradigm and also using a self-reported rating of difficulty scale. In the dual-task measure, participants were asked to repeat monosyllabic words while at the same time press a button in response to a visual stimulus. Participants were tested in two baseline conditions (speech perception alone and visual task alone) and in the following experimental conditions: (1) quiet with an omnidirectional microphone, (2) noise with an omnidirectional microphone, (3) noise with a directional microphone, and (4) noise with a directional microphone and with a second sided CI or hearing aid. When present, the noise was fixed with a +5?dB signal-to-noise ratio. After each listening condition, the participants rated the degree of listening difficulty.

Results: Changing the microphone from omni to directional mode significantly enhanced speech recognition in noise performance. There were no significant changes in speech recognition between the unilateral and bimodal/bilateral CI listening conditions. Listening effort, as measured by reaction time, increased significantly between the baseline and omnidirectional quiet listening condition though did not change significantly across the remaining listening conditions. Self-perceived listening effort revealed a greater effort for the noisy conditions, and reduced effort with the move from an omni to a directional microphone.

Conclusions: Directional microphones significantly improve speech in noise recognition over omnidirectional microphones and allowed for decreased self-perceived listening effort. The dual task used in this study failed to show any differences in listening effort across the experimental conditions and may not be sensitive enough to detect changes in listening effort.     

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.     

The effects of asymmetric directional microphone fittings on acceptance of background noise

Abstract

Objective: The effects of asymmetric directional microphone fittings (i.e., an omnidirectional microphone on one ear and a directional microphone on the other) on speech understanding in noise and acceptance of background noise were investigated in 15 full-time hearing aid users. Design: Subjects were fitted binaurally with four directional microphone conditions (i.e., binaural omnidirectional, right asymmetric directional, left asymmetric directional and binaural directional microphones) using Siemens Intuis Directional behind-the-ear hearing aids. Speech understanding in noise was assessed using the Hearing in Noise Test, and acceptance of background noise was assessed using the Acceptable Noise Level procedure. Speech was presented from 0° while noise was presented from 180° azimuth. Results/Conclusions: The results revealed that speech understanding in noise improved when using asymmetric directional microphones compared to binaural omnidirectional microphone fittings and was not significantly hindered compared to binaural directional microphone fittings. The results also revealed that listeners accepted more background noise when fitted with asymmetric directional microphones as compared to binaural omnidirectional microphones. Lastly, the results revealed that the acceptance of noise was further increased for the binaural directional microphones when compared to the asymmetric directional microphones, maximizing listeners' willingness to accept background noise in the presence of noise. Clinical implications will be discussed.

Sumario

Objetivo: Se investigaron los efectos de la adaptación de micrófonos asimétricos direccionales (i.e., un micrófono omnidireccional en un oído y uno direccional en el otro) sobre la comprensión del lenguaje en ruido y la aceptación del ruido de fondo en 15 usuarios de auxiliares auditivos de tiempo completo. Diseño: A los sujetos se les adaptaron binauralmente micrófonos direccionales en cuatro condiciones: (i.e., binaural omnidireccional, direccional derecho asimétrico, izquierdo direccional asimétrico y binaural direccional) utilizando los auxiliares auditivos tipo retroauricular Siemens Intuis Direccional. La comprensión del lenguaje en ruido fue evaluada utilizando la Prueba de Audición en Ruido y la aceptación del ruido de fondo fue evaluada utilizando el procedimiento de Nivel de Ruido Aceptable. El lenguaje se presentó a 0° mientras que el ruido se presentó a un azimut de 180°. Resultados/Conclusiones: Los resultados revelan que la comprensión del lenguaje en ruido mejoró cuando se utilizan micrófonos direccionales asimétricamente, en comparación con los micrófonos omnidireccionales en forma binaural y no se dificultó significativamente al compararse con los micrófonos direccionales en forma binaural. Estos resultados también revelaron que los oyentes aceptan mayor ruido de fondo cuando se les adaptan micrófonos asimétricos direccionales en comparación con los micrófonos omnidireccionales en forma binaural. Por ultimo, los resultados revelan que la aceptación de ruido aumentó con los micrófonos direccionales bianurales cuando se compararon con los micrófonos direccionales asimétricos, maximizando la disposición de los oyentes para aceptar el ruido de fondo en presencia de ruido. Las implicaciones clínicas serán discutidas.     

Speech recognition and comfort using hearing instruments with adaptive directional characteristics in asymmetric listening conditions

OBJECTIVE: Hearing instruments with adaptive directional microphone systems attempt to maximize speech-to-noise ratio (SNR) and thereby improve speech recognition in noisy backgrounds. When instruments with adaptive systems are fitted bilaterally, there is the potential for adverse effects as they operate independently and may give confusing cues or disturbing effects. The present study compared speech recognition performance in 16 listeners fitted bilaterally with the Phonak Claro hearing instrument using omni-directional, fixed directional, and adaptive directional microphone settings as well as mixed microphone settings (an omni-directional microphone on one side and an adaptive directional microphone on the other). DESIGN: Under anechoic conditions, speech was always presented from a loudspeaker directly in front of the listener (0 degree azimuth) whereas noise was presented from one or two loudspeakers arranged either symmetrically (0, 180, 90 + 270 degrees) or asymmetrically (170 + 240 degrees and 120 + 190 degrees) in the horizontal plane. Adaptive sentence recognition in noise measurement was supplemented by quality ratings. RESULTS: With symmetrical omni-directional settings (Omni/Omni), performance was poorer than a control group of 14 listeners with normal hearing tested unaided: Aided listeners required 4.3 dB more favorable SNR for criterion performance. In all loudspeaker arrangements in which directional characteristics could be exploited, performance with symmetrical adaptive microphones (Adapt/Adapt) was similar to the control group. The mixed microphone settings did not appear to confer any particular disadvantage for speech recognition from their asymmetric nature, always giving scores significantly better than Omni/Omni. Quality rating scores were consistent with speech recognition performance, showing benefits in terms of clarity and comfort for the Adapt/Adapt and Fixed/Fixed microphone conditions over the Omni/Omni and mixed microphone conditions wherever directional characteristics could be used. Similarly, the mixed microphone conditions were rated more comfortable and quieter for the noise than Omni/Omni. CONCLUSIONS: It is concluded that bilateral hearing instruments with adaptive directional microphones confer benefits in terms of speech recognition in noise and sound quality. Independence of the two adaptive control systems does not appear to cause untoward effects.