Department of Otolaryngology-Head & Neck Surgery, New York University Grossman School of Medicine, 550 First Avenue, New York, New York 10016, USA.
J Acoust Soc Am. 2021 Oct;150(4):2316. doi: 10.1121/10.0006446.
Binaural unmasking, a key feature of normal binaural hearing, can refer to the improved intelligibility of masked speech by adding masking that facilitates perceived separation of target and masker. A question relevant for cochlear implant users with single-sided deafness (SSD-CI) is whether binaural unmasking can still be achieved if the additional masking is spectrally degraded and shifted. CIs restore some aspects of binaural hearing to these listeners, although binaural unmasking remains limited. Notably, these listeners may experience a mismatch between the frequency information perceived through the CI and that perceived by their normal hearing ear. Employing acoustic simulations of SSD-CI with normal hearing listeners, the present study confirms a previous simulation study that binaural unmasking is severely limited when interaural frequency mismatch between the input frequency range and simulated place of stimulation exceeds 1-2 mm. The present study also shows that binaural unmasking is largely retained when the input frequency range is adjusted to match simulated place of stimulation, even at the expense of removing low-frequency information. This result bears implications for the mechanisms driving the type of binaural unmasking of the present study and for mapping the frequency range of the CI speech processor in SSD-CI users.
双耳掩蔽，正常双耳听觉的一个关键特征，可以指通过添加掩蔽来提高掩蔽语音的可懂度，从而有助于感知目标和掩蔽之间的分离。对于单侧聋（SSD-CI）的人工耳蜗使用者来说，一个相关的问题是，如果额外的掩蔽在频谱上退化和移位，是否仍然可以实现双耳掩蔽。人工耳蜗恢复了这些听众的一些双耳听觉方面的功能，尽管双耳掩蔽仍然受到限制。值得注意的是，这些听众可能会经历通过人工耳蜗感知到的频率信息与正常听力耳感知到的频率信息之间的不匹配。本研究通过对单侧聋的正常人进行声学模拟，证实了之前的一项模拟研究，即在输入频率范围和模拟刺激位置之间的耳间频率失配超过 1-2 毫米时，双耳掩蔽会受到严重限制。本研究还表明，即使以牺牲低频信息为代价，当输入频率范围调整以匹配模拟刺激位置时，双耳掩蔽也能基本保留。这一结果对驱动本研究中双耳掩蔽的机制以及在单侧聋人工耳蜗使用者中人工耳蜗言语处理器的频率范围映射具有重要意义。
