Sharma Snandan, Mens Lucas H M, Snik Ad F M, van Opstal A John, van Wanrooij Marc M
Department of Biophysics, Donders Institute for Brain, Cognition and Behavior, Radboud University, Nijmegen, Netherlands.
Department of Otorhinolaryngology, Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, Nijmegen, Netherlands.
Front Neurol. 2019 Jun 21;10:637. doi: 10.3389/fneur.2019.00637. eCollection 2019.
This study describes sound localization and speech-recognition-in-noise abilities of a cochlear-implant user with electro-acoustic stimulation (EAS) in one ear, and a hearing aid in the contralateral ear. This listener had low-frequency, up to 250 Hz, residual hearing within the normal range in both ears. The objective was to determine how hearing devices affect spatial hearing for an individual with substantial unaided low-frequency residual hearing. Sound-localization performance was assessed for three sounds with different bandpass characteristics: low center frequency (100-400 Hz), mid center frequency (500-1,500 Hz) and high frequency broad-band (500-20,000 Hz) noise. Speech recognition was assessed with the Dutch Matrix sentence test presented in noise. Tests were performed while the listener used several on-off combinations of the devices. The listener localized low-center frequency sounds well in all hearing conditions, but mid-center frequency and high frequency broadband sounds were localized well almost exclusively in the completely unaided condition (mid-center frequency sounds were also localized well with the EAS device alone). Speech recognition was best in the fully aided condition with speech presented in the front and noise presented at either side. Furthermore, there was no significant improvement in speech recognition with all devices on, compared to when the listener used her cochlear implant only. Hearing aids and cochlear implant impair high frequency spatial hearing due to improper weighing of interaural time and level difference cues. The results reinforce the notion that hearing symmetry is important for sound localization. The symmetry is perturbed by the hearing devices for higher frequencies. Speech recognition depends mainly on hearing through the cochlear implant and is not significantly improved with the added information from hearing aids. A contralateral hearing aid provides benefit when the noise is spatially separated from the speech. However, this benefit is explained by the head shadow in that ear, rather than by an ability to spatially segregate noise from speech, as sound localization was perturbed with all devices in use.
本研究描述了一名一侧耳朵使用电声刺激（EAS）的人工耳蜗使用者和对侧耳朵使用助听器时的声音定位及噪声环境下语音识别能力。该受试者双耳低频（最高250Hz）残余听力处于正常范围。目的是确定听力设备如何影响低频残余听力良好的个体的空间听觉。针对三种具有不同带通特性的声音评估了声音定位性能：低中心频率（100 - 400Hz）、中中心频率（500 - 1500Hz）和高频宽带（500 - 20000Hz）噪声。使用荷兰语矩阵句子测试在噪声环境下评估语音识别。测试在受试者使用设备的几种开关组合时进行。受试者在所有听力条件下对低中心频率声音定位良好，但中中心频率和高频宽带声音几乎仅在完全不使用设备的条件下定位良好（单独使用EAS设备时中中心频率声音定位也良好）。当语音从正面呈现且噪声从两侧呈现时，全辅助条件下语音识别最佳。此外，与仅使用人工耳蜗时相比，所有设备都开启时语音识别没有显著改善。助听器和人工耳蜗由于双耳时间和强度差线索的权重不当而损害高频空间听觉。结果强化了听力对称性对声音定位很重要这一观点。对于较高频率，听力设备会干扰这种对称性。语音识别主要取决于通过人工耳蜗的听力，并且不会因助听器增加的信息而显著改善。当噪声在空间上与语音分离时，对侧助听器会带来益处。然而，这种益处是由该耳的头影效应解释的，而不是通过从空间上分离噪声和语音的能力，因为在使用所有设备时声音定位都会受到干扰。
