Stone Michael A, Moore Brian C J
Department of Experimental Psychology, University of Cambridge, Downing Street, Cambridge CB2 3EB, United Kingdom.
J Acoust Soc Am. 2007 Mar;121(3):1654-64. doi: 10.1121/1.2434754.
Fast-acting compression has several effects on the envelope of speech signals, especially when a target and a background are mixed together. Three measures of the envelope are described, which can be used to quantify these changes: (1) Within-signal modulation correlation or coherence, the degree of correlation (or coherence) of the envelope (on a dB scale) of a single source across different frequency regions, which is reduced by fast-acting compression; (2) fidelity of envelope shape, the degree to which the envelope shape of the target speech in different frequency channels is preserved following compression; and (3) across-signal modulation correlation or coherence (ASMC), the extent to which the target and background acquire a common component of modulation when they are compressed together, which becomes greater in absolute value (more negative) when the target and background are compressed together. Values of these measures are presented and compared with intelligibility scores obtained using stimuli processed (with a noise-vocoder) so as to preserve mainly envelope cues in a limited number of frequency channels. The results suggest that the dominant factor affecting intelligibility is ASMC.
快速起效压缩对语音信号的包络有多种影响，尤其是当目标信号和背景信号混合在一起时。文中描述了包络的三种测量方法，可用于量化这些变化：（1）信号内调制相关性或相干性，即单个声源包络（以分贝为单位）在不同频率区域的相关程度（或相干程度），快速起效压缩会降低该相关性；（2）包络形状保真度，即压缩后不同频率通道中目标语音包络形状的保留程度；（3）跨信号调制相关性或相干性（ASMC），即目标信号和背景信号一起压缩时，它们获得共同调制成分的程度，当目标信号和背景信号一起压缩时，该值的绝对值会变得更大（更负）。文中给出了这些测量方法的值，并与使用（通过噪声声码器）处理过的刺激所获得的可懂度分数进行比较，以便在有限数量的频率通道中主要保留包络线索。结果表明，影响可懂度的主要因素是ASMC。
