Department of Otolaryngology, Medical University Hannover and Cluster of Excellence Hearing4all, Hanover, Germany.
Department of Otorhinolaryngology, University Medical Center Groningen, University of Groningen, Groningen, Netherlands.
Trends Hear. 2021 Jan-Dec;25:23312165211030166. doi: 10.1177/23312165211030166.
Speech intelligibility in multitalker settings is challenging for most cochlear implant (CI) users. One possibility for this limitation is the suboptimal representation of vocal cues in implant processing, such as the fundamental frequency (F0), and the vocal tract length (VTL). Previous studies suggested that while F0 perception depends on spectrotemporal cues, VTL perception relies largely on spectral cues. To investigate how spectral smearing in CIs affects vocal cue perception in speech-on-speech (SoS) settings, adjacent electrodes were simultaneously stimulated using current steering in 12 Advanced Bionics users to simulate channel interaction. In current steering, two adjacent electrodes are simultaneously stimulated forming a channel of parallel stimulation. Three such stimulation patterns were used: Sequential (one current steering channel), Paired (two channels), and Triplet stimulation (three channels). F0 and VTL just-noticeable differences (JNDs; Task 1), in addition to SoS intelligibility (Task 2) and comprehension (Task 3), were measured for each stimulation strategy. In Tasks 2 and 3, four maskers were used: the same female talker, a male voice obtained by manipulating both F0 and VTL (F0+VTL) of the original female speaker, a voice where only F0 was manipulated, and a voice where only VTL was manipulated. JNDs were measured relative to the original voice for the F0, VTL, and F0+VTL manipulations. When spectral smearing was increased from Sequential to Triplet, a significant deterioration in performance was observed for Tasks 1 and 2, with no differences between Sequential and Paired stimulation. Data from Task 3 were inconclusive. These results imply that CI users may tolerate certain amounts of channel interaction without significant reduction in performance on tasks relying on voice perception. This points to possibilities for using parallel stimulation in CIs for reducing power consumption.
多说话人环境下的言语可懂度对大多数人工耳蜗（CI）用户来说具有挑战性。这种限制的一个可能原因是植入物处理中声音线索的表示不理想，例如基频（F0）和声道长度（VTL）。先前的研究表明，虽然 F0 感知取决于时频谱线索，但 VTL 感知主要依赖于频谱线索。为了研究 CI 中的频谱模糊如何影响语音对语音（SoS）环境中的声音线索感知，12 名 Advanced Bionics 用户使用电流转向同时刺激相邻电极，以模拟通道间相互作用。在电流转向中，两个相邻电极同时被刺激形成平行刺激的通道。使用了三种这种刺激模式：顺序（一个电流转向通道）、成对（两个通道）和三联刺激（三个通道）。每个刺激策略都测量了 F0 和 VTL 可察觉差异（JND；任务 1），以及 SoS 可懂度（任务 2）和理解（任务 3）。在任务 2 和 3 中，使用了四个掩蔽器：同一个女性说话者、通过操纵原始女性说话者的 F0 和 VTL（F0+VTL）获得的男性声音、仅操纵 F0 的声音以及仅操纵 VTL 的声音。JND 是相对于原始声音测量的 F0、VTL 和 F0+VTL 操作。当频谱模糊度从顺序增加到三联时，观察到任务 1 和 2 的性能显著恶化，而顺序和成对刺激之间没有差异。任务 3 的数据没有定论。这些结果表明，CI 用户可能可以容忍一定程度的通道间相互作用，而不会导致依赖语音感知的任务性能显著下降。这为在 CI 中使用并行刺激以降低功耗提供了可能性。
