Moore B C, Schooneveldt G P
Department of Experimental Psychology, University of Cambridge, England.
J Acoust Soc Am. 1990 Aug;88(2):725-31. doi: 10.1121/1.399775.
The threshold for a signal masked by a narrow band of noise centered at the signal frequency (the on-frequency band) may be reduced by adding to the masker a second band of noise (the flanking band) whose envelope is correlated with that of the first band, an effect called comodulation masking release (CMR). This paper examines CMR as a function of masker bandwidth and time delay between the envelopes of the on-frequency and flanking bands. The 1.0-kHz sinusoidal signal had a duration of 400 ms. The on-frequency band was presented alone (reference condition) or with the flanking band. The flanking-band envelope was either correlated or uncorrelated with that of the on-frequency band. Flanking-band center frequencies ranged from 0.25-2.0 kHz. The flanking band was presented either in the same ear as the on-frequency band (monaural condition) or in the opposite ear (dichotic condition). The noise bands had bandwidths of 6.25, 25, or 100 Hz. In the correlated conditions, the flanking-band envelope was delayed with respect to that of the on-frequency band by 0, 5, 10, or 20 ms. For the 100-Hz bandwidth, CMRs were small (typically less than 1 dB) in both monaural and dichotic conditions at all delay times. For the 25-Hz bandwidth, CMRs were about 3.5 dB for the 0-ms delay, and decreased to about 1.5 dB for the 20-ms delay. For the 6.25-Hz bandwidth, CMRs averaged about 5 dB and were almost independent of delay time. The results suggest that the absolute delay time is not the critical variable determining CMR. The magnitude of CMR appears to depend on the correlation between the envelopes of the on-frequency and flanking bands. However, the results do not support a model of CMR that assumes that signal threshold corresponds to a constant change in across-band envelope correlation when the correlation is transformed to Fisher's z.
以信号频率为中心的窄带噪声（即中心频率带）所掩蔽的信号阈值，可通过向掩蔽器添加第二个噪声带（即侧翼带）来降低，该侧翼带的包络与第一个噪声带的包络相关，这种效应称为共调制掩蔽释放（CMR）。本文研究了CMR作为掩蔽器带宽以及中心频率带和侧翼带包络之间时间延迟的函数。1.0千赫的正弦信号持续时间为400毫秒。中心频率带单独呈现（参考条件）或与侧翼带一起呈现。侧翼带包络与中心频率带的包络相关或不相关。侧翼带中心频率范围为0.25 - 2.0千赫。侧翼带与中心频率带在同一耳呈现（单耳条件）或在对侧耳呈现（双耳条件）。噪声带的带宽为6.25、25或100赫兹。在相关条件下，侧翼带包络相对于中心频率带的包络延迟0、5、10或20毫秒。对于100赫兹带宽，在所有延迟时间下，单耳和双耳条件下的CMR都很小（通常小于1分贝）。对于25赫兹带宽，0毫秒延迟时CMR约为3.5分贝，20毫秒延迟时降至约1.5分贝。对于6.25赫兹带宽，CMR平均约为5分贝，且几乎与延迟时间无关。结果表明，绝对延迟时间不是决定CMR的关键变量。CMR的大小似乎取决于中心频率带和侧翼带包络之间的相关性。然而，结果并不支持一种CMR模型，该模型假设当相关性转换为费希尔z值时，信号阈值对应于跨带包络相关性的恒定变化。
