Fu Q J, Shannon R V, Wang X
Department of Auditory Implants and Perception, House Ear Institute, Los Angeles, California 90057, USA.
J Acoust Soc Am. 1998 Dec;104(6):3586-96. doi: 10.1121/1.423941.
Current multichannel cochlear implant devices provide high levels of speech performance in quiet. However, performance deteriorates rapidly with increasing levels of background noise. The goal of this study was to investigate whether the noise susceptibility of cochlear implant users is primarily due to the loss of fine spectral information. Recognition of vowels and consonants was measured as a function of signal-to-noise ratio in four normal-hearing listeners in conditions simulating cochlear implants with both CIS and SPEAK-like strategies. Six conditions were evaluated: 3-, 4-, 8-, and 16-band processors (CIS-like), a 6/20 band processor (SPEAK-like), and unprocessed speech. Recognition scores for vowels and consonants decreased as the S/N level worsened in all conditions, as expected. Phoneme recognition threshold (PRT) was defined as the S/N at which the recognition score fell to 50% of its level in quiet. The unprocessed speech had the best PRT, which worsened as the number of bands decreased. Recognition of vowels and consonants was further measured in three Nucleus-22 cochlear implant users using either their normal SPEAK speech processor or a custom processor with a four-channel CIS strategy. The best cochlear implant user showed similar performance with the CIS strategy in quiet and in noise to that of normal-hearing listeners when listening to correspondingly spectrally degraded speech. These findings suggest that the noise susceptibility of cochlear implant users is at least partly due to the loss of spectral resolution. Efforts to improve the effective number of spectral information channels should improve implant performance in noise.
当前的多通道人工耳蜗装置在安静环境中能提供高水平的言语表现。然而，随着背景噪声水平的增加，其表现会迅速恶化。本研究的目的是调查人工耳蜗使用者对噪声的易感性是否主要归因于精细频谱信息的丧失。在模拟采用CIS和类似SPEAK策略的人工耳蜗的条件下，测量了四名听力正常的受试者中元音和辅音的识别率与信噪比的函数关系。评估了六种情况：3频段、4频段、8频段和16频段处理器（类似CIS）、6/20频段处理器（类似SPEAK）以及未处理的语音。正如预期的那样，在所有情况下，随着信噪比水平的恶化，元音和辅音的识别分数均下降。音素识别阈值（PRT）被定义为识别分数降至其安静环境水平的50%时的信噪比。未处理的语音具有最佳的PRT，随着频段数量的减少，PRT会变差。使用他们正常的SPEAK语音处理器或具有四通道CIS策略的定制处理器，进一步测量了三名Nucleus-22人工耳蜗使用者中元音和辅音的识别情况。当聆听相应频谱退化的语音时，最佳的人工耳蜗使用者在安静和噪声环境中使用CIS策略时，其表现与听力正常的受试者相似。这些发现表明，人工耳蜗使用者对噪声的易感性至少部分归因于频谱分辨率的丧失。提高频谱信息通道有效数量的努力应能改善人工耳蜗在噪声环境中的表现。
