Hall J W, Haggard M P, Fernandes M A
J Acoust Soc Am. 1984 Jul;76(1):50-6. doi: 10.1121/1.391005.
Detectability of a 400-ms, 1000-Hz pure-tone signal was examined in bandlimited noise where different spectral regions were given similar waveform envelope characteristics. As expected, in random noise the threshold increased as the noise bandwidth was increased up to a critical bandwidth, but remained constant for further increases in bandwidth. In the noise with envelope coherence however, threshold decreased when the noise bandwidth was made wider than the critical bandwidth. The improvement in detectability was attributed to a process by which energy outside the critical band is used to help differentiate signal from masking noise, provided that the waveform envelope characteristics of the noise inside and outside the critical band are similar. With flanking coherent noise bands either lower or higher in frequency than a noise band centered on the signal, it was next determined that the frequency relation and remoteness of the coherent noise did not particularly influence the magnitude of the unmasking effect. An interpretation in terms of nonsimultaneous masking was reconciled with some aspects of the data, and with an interpretation in terms of across-frequency temporal pattern analysis. This paradigm, in which detection is based upon across-frequency temporal envelope coherence, was termed "comodulation masking release." Comodulation offers a controlled way to investigate some of the mechanisms which permit signals to be detected at adverse signal-to-noise ratios.
在具有相似波形包络特征的不同频谱区域的带限噪声中，对400毫秒、1000赫兹纯音信号的可检测性进行了研究。正如预期的那样，在随机噪声中，随着噪声带宽增加到临界带宽，阈值会升高，但当带宽进一步增加时，阈值保持不变。然而，在具有包络相干性的噪声中，当噪声带宽比临界带宽更宽时，阈值会降低。可检测性的提高归因于这样一个过程：临界带外的能量被用来帮助区分信号和掩蔽噪声，前提是临界带内和带外噪声的波形包络特征相似。对于位于信号中心频率两侧、频率低于或高于该信号中心频率的相干噪声带，接下来确定相干噪声的频率关系和距离对解掩蔽效应的大小没有特别影响。根据非同时掩蔽进行的解释与部分数据相吻合，也与根据跨频率时间模式分析进行的解释相符。这种基于跨频率时间包络相干性进行检测的范式被称为“共调制掩蔽释放”。共调制提供了一种可控的方法来研究一些允许在不利信噪比下检测信号的机制。
