University of Groningen, University Medical Center Groningen, Department of Otorhinolaryngology/Head and Neck Surgery, Groningen, The Netherlands.
J Acoust Soc Am. 2018 Jun;143(6):3505. doi: 10.1121/1.5041261.
The vocal tract length (VTL) of a speaker is an important voice cue that aids speech intelligibility in multi-talker situations. However, cochlear implant (CI) users demonstrate poor VTL sensitivity. This may be partially caused by the mismatch between frequencies received by the implant and those corresponding to places of stimulation along the cochlea. This mismatch can distort formant spacing, where VTL cues are encoded. In this study, the effects of frequency mismatch and band partitioning on VTL sensitivity were investigated in normal hearing listeners with vocoder simulations of CI processing. The hypotheses were that VTL sensitivity may be reduced by increased frequency mismatch and insufficient spectral resolution in how the frequency range is partitioned, specifically where formants lie. Moreover, optimal band partitioning might mitigate the detrimental effects of frequency mismatch on VTL sensitivity. Results showed that VTL sensitivity decreased with increased frequency mismatch and reduced spectral resolution near the low frequencies of the band partitioning map. Band partitioning was independent of mismatch, indicating that if a given partitioning is suboptimal, a better partitioning might improve VTL sensitivity despite the degree of mismatch. These findings suggest that customizing the frequency partitioning map may enhance VTL perception in individual CI users.
声道长度（VTL）是说话人重要的语音线索之一，有助于在多说话人情况下提高语音可懂度。然而，人工耳蜗（CI）使用者表现出对 VTL 的敏感性较差。这可能部分是由于植入物接收到的频率与耳蜗中刺激部位相对应的频率不匹配所致。这种失配会扭曲共振峰间距，而 VTL 线索就是通过共振峰间距进行编码的。在这项研究中，通过对 CI 处理的声码器模拟，研究了正常听力者中频率失配和频带划分对 VTL 敏感性的影响。假设是，随着频率失配的增加和频带划分方式中频谱分辨率的降低（特别是在共振峰所在的位置），VTL 敏感性可能会降低。此外，最佳的频带划分可能会减轻频率失配对 VTL 敏感性的不利影响。结果表明，VTL 敏感性随频率失配的增加和频带划分图低频附近频谱分辨率的降低而降低。频带划分与失配无关，这表明如果给定的划分是次优的，那么即使失配程度较大，更好的划分也可能提高 VTL 敏感性。这些发现表明，定制频率划分图可能会增强个体 CI 用户的 VTL 感知。
