Zurek P M
J Acoust Soc Am. 1979 Dec;66(6):1751-7. doi: 10.1121/1.383648.
The notion of binaural echo suppression that has persisted through the years states that when listening binaurally, the effects of reverberation (spectral modulation or coloration) are less noticeable than when listening with one ear only. This idea was tested in the present study by measuring thresholds for detection of an echo of a diotic noise masker with the echo presented with either a zero or a 500-musec interaural delay. With echo delays less than 5-10 msec, thresholds for the diotic echo were about 10 dB lower than for the dichotic signal, a finding opposite that of the usual binaural masking-level difference but consistent with the notion of binaural echo suppression. Additional echo-threshold measurements were made with echoes of interaurally reversed polarity, producing out-of-phase spectral modulations. The 10-15 dB increase in thresholds for the reverse-polarity echo, over those for the same-polarity echo, indicated that the apparent "hollowness" associated with spectral modulations can be partially canceled centrally. Overall, the results of this study are consistent with a model in which: (1) the monaural representations of spectral magnitude are nonlinearly compressed prior to being combined centrally; and (2) neither monaural channel can be isolated in order to perform the detection task.
多年来一直存在的双耳回声抑制概念表明，与单耳聆听相比，双耳聆听时混响（频谱调制或染色）的影响不太明显。在本研究中，通过测量双耳噪声掩蔽器回声的检测阈值来验证这一观点，回声呈现为零或500微秒的耳间延迟。当回声延迟小于5 - 10毫秒时，双耳回声的阈值比双耳信号的阈值低约10分贝，这一发现与通常的双耳掩蔽级差相反，但与双耳回声抑制概念一致。还对耳间极性反转的回声进行了额外的回声阈值测量，产生异相频谱调制。与同极性回声相比，反极性回声的阈值增加了10 - 15分贝，这表明与频谱调制相关的明显“空洞感”可以在中枢部分抵消。总体而言，本研究结果与一个模型一致，在该模型中：（1）频谱幅度的单耳表征在中枢合并之前进行非线性压缩；（2）为了执行检测任务，无法分离任何一个单耳通道。
