McCall D D, Freyman R L, Clifton R K
University of Massachusetts, Amherst 01003, USA.
Percept Psychophys. 1998 May;60(4):593-601. doi: 10.3758/bf03206048.
The effect of changing the frequency components of an echo relative to the sound source was examined in a two-choice discrimination task. Subjects sat in an anechoic chamber and discriminated the direction of the lag noise burst within a lead-lag pair presented over loudspeakers. The leading noise burst was broadband, and the lagging burst was either high- or low-pass filtered. On some conditions, this test burst pair was preceded by a conditioning train of burst pairs, which also had a broadband lead and either a high- or low-frequency lag. When the frequency content of the echo was held constant across the conditioning train and test burst pair, echo suppression that was built up during the repeating train was maintained for the test burst pair, shown by the subjects' poor performance in detecting the location of the lagging burst. By comparison, subjects had little difficulty in localizing the lagging burst when the frequency content of the echo changed between the conditioning train and the test burst, indicating that any buildup of suppression during the train was broken when the lagging burst's spectrum shifted. The data are consistent with an interpretation in which echo suppression is temporarily broken when listeners' built-up expectations about room acoustics are violated.
在一项二选一辨别任务中，研究了改变回声相对于声源的频率成分所产生的影响。受试者坐在消声室内，辨别通过扬声器呈现的超前-滞后噪声脉冲对中滞后噪声脉冲的方向。超前噪声脉冲是宽带的，而滞后脉冲经过了高通或低通滤波。在某些条件下，这个测试脉冲对之前有一系列条件脉冲对，这些条件脉冲对也有一个宽带超前脉冲和一个高频或低频滞后脉冲。当回声的频率成分在整个条件脉冲对序列和测试脉冲对中保持恒定时，在重复序列中建立起来的回声抑制作用在测试脉冲对中得以维持，这表现为受试者在检测滞后脉冲位置时表现不佳。相比之下，当回声的频率成分在条件脉冲对序列和测试脉冲对之间发生变化时，受试者在定位滞后脉冲时几乎没有困难，这表明当滞后脉冲的频谱发生偏移时，序列中任何抑制作用的积累都会被打破。这些数据与一种解释一致，即当听众对房间声学的既定预期被违反时，回声抑制会暂时被打破。
