Poon Becky B, Eddington Donald K, Noel Victor, Colburn H Steven
Cochlear Implant Research Laboratory, Massachusetts Eye and Ear Infirmary, Boston, MA 02114, USA.
J Acoust Soc Am. 2009 Aug;126(2):806-15. doi: 10.1121/1.3158821.
Sensitivity to interaural time difference (ITD) in constant-amplitude pulse trains was measured in four sequentially implanted bilateral cochlear implant (CI) subjects. The sensitivity measurements were made as a function of time beginning directly after the second ear was implanted, continued for periods of months before subjects began wearing bilateral sound processors, and extended for months while the subjects used bilateral sound processors in day-to-day listening. Measurements were also made as a function of the relative position of the left/right electrodes. The two subjects with the shortest duration of binaural deprivation before implantation demonstrated ITD sensitivity soon after second-ear implantation (before receiving the second sound processor), while the other two did not demonstrate sensitivity until after months of daily experience using bilateral processors. The interaural mismatch in electrode position required to decrease ITD sensitivity by a factor of 2 (half-width) for CI subjects was five times greater than the half-width for interaural carrier-frequency disparity in normal-hearing subjects listening to sinusoidally amplitude-modulated high-frequency tones. This large half-width is likely to contribute to poor binaural performance in CI users, especially in environments with multiple broadband sound sources.
在四名依次接受双侧人工耳蜗（CI）植入的受试者中，测量了他们对恒定振幅脉冲序列的双耳时间差（ITD）敏感度。敏感度测量是从第二只耳朵植入后立即开始，作为时间的函数进行，在受试者开始佩戴双侧声音处理器之前持续数月，并在受试者日常聆听中使用双侧声音处理器时再延长数月。测量还作为左右电极相对位置的函数进行。在植入前双耳剥夺时间最短的两名受试者在第二只耳朵植入后不久（在收到第二个声音处理器之前）就表现出ITD敏感度，而另外两名受试者直到使用双侧处理器数月后才有敏感度表现。对于CI受试者，将ITD敏感度降低一半（半高宽）所需的电极位置双耳不匹配比正常听力受试者聆听正弦调幅高频音时双耳载波频率差异的半高宽大五倍。这种大的半高宽可能导致CI使用者的双耳性能较差，尤其是在有多个宽带声源的环境中。
