Division of Communication and Auditory Neuroscience, House Research Institute, Los Angeles, CA, USA.
Ear Hear. 2013 May-Jun;34(3):273-9. doi: 10.1097/AUD.0b013e31826709e8.
This study investigated whether a spectral mismatch across ears influences the benefit of redundancy, squelch, and head shadow differently in speech perception using acoustic simulation of bilateral cochlear implant (CI) processing.
Ten normal-hearing subjects participated in the study, and acoustic simulations of CIs were used to test these subjects. Sentence recognition, presented unilaterally and bilaterally, was measured at +5 dB and +10 dB signal-to-noise ratios (SNRs) with bilaterally matched and mismatched conditions. Unilateral and bilateral CIs were simulated using 8-channel sine wave vocoders. Binaural spectral mismatch was introduced by changing the relative simulated insertion depths across ears. Subjects were tested while listening with headphones; head-related transfer functions were applied before the vocoder processing to preserve natural interaural level and time differences.
For both SNRs, greater and more consistent binaural benefit of squelch and redundancy occurred for the matched condition whereas binaural interference of squelch and redundancy occurred for the mismatched condition. However, significant binaural benefit of head shadow existed irrespective of spectral mismatches and SNRs.
The results suggest that bilateral spectral mismatch may have a negative impact on the binaural benefit of squelch and redundancy for bilateral CI users. The results also suggest that clinical mapping should be carefully administrated for bilateral CI users to minimize the difference in spectral patterns between the two CIs.
本研究通过双耳仿生人工耳蜗处理的声学模拟，考察了双耳间频谱失配是否会对冗余抑制和头部遮蔽的增益产生不同影响，从而影响言语感知。
本研究纳入 10 名正常听力受试者，采用人工耳蜗声学模拟对其进行测试。在+5 dB 和+10 dB 信噪比条件下，分别对单侧和双侧呈现的句子识别进行测量，模拟双侧匹配和失配条件。使用 8 通道正弦波声码器模拟单侧和双侧人工耳蜗。通过改变双耳间相对插入深度来引入双耳频谱失配。受试者在头戴式耳机中进行测试，在声码器处理前应用头相关传递函数，以保留自然的双耳强度差和时间差。
对于两种信噪比，匹配条件下的冗余抑制和抑制的双耳增益更大且更一致，而失配条件下则出现双耳抑制的干扰。然而，无论频谱失配和信噪比如何，头部遮蔽的双耳增益都有显著的影响。
结果表明，双侧频谱失配对双侧人工耳蜗使用者的抑制和冗余的双耳增益可能有负面影响。结果还表明，对于双侧人工耳蜗使用者，临床映射应谨慎管理，以最小化两个人工耳蜗之间的频谱模式差异。
