Department of Otolaryngology, Medical University Hannover and Cluster of Excellence Hearing4all, Hanover, Germany.
Trends Hear. 2020 Jan-Dec;24:2331216520970349. doi: 10.1177/2331216520970349.
Cochlear implant (CI) sound processing typically uses a front-end automatic gain control (AGC), reducing the acoustic dynamic range (DR) to control the output level and protect the signal processing against large amplitude changes. It can also introduce distortions into the signal and does not allow a direct mapping between acoustic input and electric output. For speech in noise, a reduction in DR can result in lower speech intelligibility due to compressed modulations of speech. This study proposes to implement a CI signal processing scheme consisting of a full acoustic DR with adaptive properties to improve the signal-to-noise ratio and overall speech intelligibility. Measurements based on the Short-Time Objective Intelligibility measure and an electrodogram analysis, as well as behavioral tests in up to 10 CI users, were used to compare performance with a single-channel, dual-loop, front-end AGC and with an adaptive back-end multiband dynamic compensation system (Voice Guard [VG]). Speech intelligibility in quiet and at a +10 dB signal-to-noise ratio was assessed with the Hochmair-Schulz-Moser sentence test. A logatome discrimination task with different consonants was performed in quiet. Speech intelligibility was significantly higher in quiet for VG than for AGC, but intelligibility was similar in noise. Participants obtained significantly better scores with VG than AGC in the logatome discrimination task. The objective measurements predicted significantly better performance estimates for VG. Overall, a dynamic compensation system can outperform a single-stage compression (AGC + linear compression) for speech perception in quiet.
人工耳蜗（CI）声音处理通常使用前端自动增益控制（AGC），降低声动态范围（DR）以控制输出电平，并防止信号处理受到大振幅变化的影响。它还可以引入信号失真，并且不允许在声输入和电输出之间进行直接映射。对于噪声中的语音，由于语音的调制被压缩，DR 的降低会导致语音可懂度降低。本研究提出了一种 CI 信号处理方案，该方案由具有自适应特性的全声 DR 组成，以提高信噪比和整体语音可懂度。基于短时间客观可懂度测量和电描记图分析的测量，以及多达 10 名 CI 用户的行为测试，用于将性能与单通道、双环路前端 AGC 和自适应后端多频带动态补偿系统（Voice Guard [VG]）进行比较。使用 Hochmair-Schulz-Moser 句子测试评估在安静和+10dB 信噪比下的语音可懂度。在安静环境下进行不同辅音的音节辨别任务。在安静环境下，VG 的语音可懂度明显高于 AGC，但在噪声环境下两者相似。参与者在音节辨别任务中使用 VG 获得的分数明显高于 AGC。客观测量预测 VG 的性能估计明显更好。总体而言，对于安静环境下的语音感知，动态补偿系统可以胜过单级压缩（AGC+线性压缩）。
