Coding of the fundamental frequency in continuous interleaved sampling processors for cochlear implants
Coding of the fundamental frequency in continuous interleaved sampling processors for cochlear implants
复制标题
DOI：
10.1121/1.1340650
复制
发表时间：
2001-02-01
影响因子：
2.4
通讯作者：
Wouters, J
中科院分区：
文献类型：
--
作者：
Geurts, L;Wouters, J
本研究探讨了人工耳蜗者对周期性刺激基频(F0)的感知。一种广泛使用的语音处理器是连续交织采样(CIS)处理器，其基频表现为输出端包络中的时间波动。对Laura(飞利浦听力植入物的注册商标，现为欧洲人工耳蜗技术中心)的四个用户进行了三个实验，以检查这些包络波动的调制深度对基音识别的影响。在第一个实验中，受试者被要求区分调制频率不同(Deltaf=20%)的单个电极通道上的两个正弦幅度调制(SAM)脉冲串。正如预期的那样，结果表明，在较小的调制深度时，性能有所下降。根据受试者、电极通道和调制频率的不同，调制深度在20%到99%之间时达到最佳性能。在第二个实验中，测量了三种算法的合成元音F0的最小显著差异，这三种算法在输出端获得的调制深度不同：默认的CIS策略，其中去除了包络中的F0波动的CIS策略(平坦CIS)，以及专门设计来控制和增加这些波动的深度的第三种CIS策略(F0 CIS)。总体而言，平坦CIS策略的性能最差，其中F0的变化仅表现为通道输出的平均幅度的变化。这强调了语音包络中F0的时间编码对于基音感知的重要性。与默认的CIS策略相比，F0 CIS策略没有获得显著更好的结果，尽管后者导致了包络调制深度，在第一个实验的某些情况下，在该包络调制深度处获得了次优分数。这表明，如果用同步F0波动激励所有通道，则需要的调制较少。这一假设在第三个实验中得到了证实，在该实验中，如果同时刺激三个通道，而不是只刺激一个通道，则受试者在使用SAM脉冲串的基音识别任务中表现明显更好。(C)2001年美国声学学会。
In this study the perception of the fundamental frequency (F0) of periodic stimuli by cochlear implant users is investigated. A widely used speech processor is the Continuous Interleaved Sampling (CIS) processor, for which the fundamental frequency appears as temporal fluctuations in the envelopes at the output. Three experiments with four users of the LAURA (Registered trade mark of Philips Hearing Implants, now Cochlear Technology Centre Europe) cochlear implant were carried out to examine the influence of the modulation depth of these envelope fluctuations on pitch discrimination. In the first experiment, the subjects were asked to discriminate between two SAM (sinusoidally amplitude modulated) pulse trains on a single electrode channel differing in modulation frequency ( deltaf = 20%). As expected, the results showed a decrease in the performance for smaller modulation depths. Optimal performance was reached for modulation depths between 20% and 99%, depending on subject, electrode channel, and modulation frequency. In the second experiment, the smallest noticeable difference in F0 of synthetic vowels was measured for three algorithms that differed in the obtained modulation depth at the output: the default CIS strategy, the CIS strategy in which the F0 fluctuations in the envelope were removed (FLAT CIS), and a third CIS strategy, which was especially designed to control and increase the depth of these fluctuations (F0 CIS). In general, performance was poorest for the FLAT CIS strategy, where changes in F0 are only apparent as changes of the average amplitude in the channel outputs. This emphasizes the importance of temporal coding of F0 in the speech envelope for pitch perception. No significantly better results were obtained for the F0 CIS strategy compared to the default CIS strategy, although the latter results in envelope modulation depths at which sub-optimal scores were obtained in some cases of the first experiment. This indicates that less modulation is needed if all channels are stimulated with synchronous F0 fluctuations. This hypothesis is confirmed in a third experiment where subjects performed significantly better in a pitch discrimination task with SAM pulse trains, if three channels were stimulated concurrently, as opposed to only one. (C) 2001 Acoustical Society of America.