Department of Physiology & Biophysics, University of Colorado School of Medicine, Aurora, CO, USA
Department of Otorhinolaryngology-Head and Neck Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
Trends Hear. 2016 Oct 3;20:2331216516668303. doi: 10.1177/2331216516668303.
In patients with bilateral hearing loss, the use of two hearing aids (HAs) offers the potential to restore the benefits of binaural hearing, including sound source localization and segregation. However, existing evidence suggests that bilateral HA users' access to binaural information, namely interaural time and level differences (ITDs and ILDs), can be compromised by device processing. Our objective was to characterize the nature and magnitude of binaural distortions caused by modern digital behind-the-ear HAs using a variety of stimuli and HA program settings. Of particular interest was a common frequency-lowering algorithm known as nonlinear frequency compression, which has not previously been assessed for its effects on binaural information. A binaural beamforming algorithm was also assessed. Wide dynamic range compression was enabled in all programs. HAs were placed on a binaural manikin, and stimuli were presented from an arc of loudspeakers inside an anechoic chamber. Stimuli were broadband noise bursts, 10-Hz sinusoidally amplitude-modulated noise bursts, or consonant-vowel-consonant speech tokens. Binaural information was analyzed in terms of ITDs, ILDs, and interaural coherence, both for whole stimuli and in a time-varying sense (i.e., within a running temporal window) across four different frequency bands (1, 2, 4, and 6 kHz). Key findings were: (a) Nonlinear frequency compression caused distortions of high-frequency envelope ITDs and significantly reduced interaural coherence. (b) For modulated stimuli, all programs caused time-varying distortion of ILDs. (c) HAs altered the relationship between ITDs and ILDs, introducing large ITD-ILD conflicts in some cases. Potential perceptual consequences of measured distortions are discussed.
在双侧听力损失的患者中，使用两个助听器（HA）有可能恢复双耳听力的益处，包括声源定位和分离。然而，现有证据表明，双侧 HA 用户获取双耳信息（即耳间时间和强度差异（ITD 和 ILD））可能会受到设备处理的影响。我们的目标是使用各种刺激和 HA 程序设置来描述现代数字耳背式 HA 引起的双耳失真的性质和程度。特别感兴趣的是一种称为非线性频率压缩的常见频率降低算法，该算法尚未评估其对双耳信息的影响。还评估了双耳波束形成算法。所有程序都启用了宽动态范围压缩。将 HA 放置在双耳人体模型上，并用来自无声室内弧形扬声器的刺激进行呈现。刺激是宽带噪声突发、10Hz 正弦幅度调制噪声突发或辅音-元音-辅音语音令牌。以 ITD、ILD 和耳间相干性的形式分析双耳信息，包括整个刺激以及在四个不同频带（1、2、4 和 6 kHz）内随时间变化的意义（即在运行的时间窗口内）。主要发现如下：（a）非线性频率压缩会导致高频包络 ITD 失真，并显着降低耳间相干性。（b）对于调制刺激，所有程序都会导致 ILD 的时变失真。（c）HA 改变了 ITD 和 ILD 之间的关系，在某些情况下会引入大的 ITD-ILD 冲突。讨论了测量失真的潜在感知后果。
