Dorman M F, Loizou P C, Fitzke J, Tu Z
Department of Speech and Hearing Science, Arizona State University, Tempe 85287-0102, USA.
J Acoust Soc Am. 1998 Dec;104(6):3583-5. doi: 10.1121/1.423940.
Sentences were processed through simulations of cochlear-implant signal processors with 6, 8, 12, 16, and 20 channels and were presented to normal-hearing listeners at +2 db S/N and at -2 db S/N. The signal-processing operations included bandpass filtering, rectification, and smoothing of the signal in each band, estimation of the rms energy of the signal in each band (computed every 4 ms), and generation of sinusoids with frequencies equal to the center frequencies of the bands and amplitudes equal to the rms levels in each band. The sinusoids were summed and presented to listeners for identification. At issue was the number of channels necessary to reach maximum performance on tests of sentence understanding. At +2 dB S/N, the performance maximum was reached with 12 channels of stimulation. At -2 dB S/N, the performance maximum was reached with 20 channels of stimulation. These results, in combination with the outcome that in quiet, asymptotic performance is reached with five channels of stimulation, demonstrate that more channels are needed in noise than in quiet to reach a high level of sentence understanding and that, as the S/N becomes poorer, more channels are needed to achieve a given level of performance.
句子通过具有6、8、12、16和20个通道的人工耳蜗信号处理器模拟进行处理，并以信噪比为+2分贝和-2分贝呈现给听力正常的听众。信号处理操作包括带通滤波、整流以及对每个频段信号的平滑处理，估计每个频段信号的均方根能量（每4毫秒计算一次），并生成频率等于频段中心频率且幅度等于每个频段均方根电平的正弦波。这些正弦波相加后呈现给听众进行识别。关键问题是在句子理解测试中达到最佳表现所需的通道数量。在信噪比为+2分贝时，12个刺激通道可达到最佳表现。在信噪比为-2分贝时，20个刺激通道可达到最佳表现。这些结果，结合在安静环境中5个刺激通道可达到渐近表现的结果，表明在噪声环境中比在安静环境中需要更多通道才能达到高水平的句子理解，并且随着信噪比变差，需要更多通道才能达到给定的表现水平。
