Green D M, Nguyen Q T
Psychology Department, University of Florida, Gainesville 32611.
Hear Res. 1988 Feb-Mar;32(2-3):147-63. doi: 10.1016/0378-5955(88)90087-1.
This paper explores how amplitude modulation influences the detection of changes in spectral shape. We generally used a complex of 21 equal-amplitude components, the lowest frequency was 200 Hz, the highest 5000 Hz, with equal logarithmic spacing between components. The signal was an increase in level of one or more components of the complex. The overall level of the sound varied randomly over a 20-dB range. Three experiments are reported. In the first, we determined how the modulation of a single-frequency component influenced the detection of amplitude change at that region. In the second experiment, the signal was an alteration of the entire spectrum and that alteration was subjected to various forms of amplitude modulation. In neither experiment did modulation generally increase the detectability of the signal. Finally, in the third experiment, we determined the effects of modulating the 'signal' and 'nonsignal' parts of the spectrum in different relative phases. The results of this experiment showed that the relative phase is important only for modulation rates slower than about 40 Hz. For faster rates, the temporal structure of the spectrum is unimportant. Thus, for modulation rates above 40 Hz, only the power spectrum of the stimulus is critical.
本文探讨了调幅如何影响频谱形状变化的检测。我们通常使用由21个等幅分量组成的复合体，最低频率为200赫兹，最高频率为5000赫兹，各分量之间具有相等的对数间距。信号是该复合体中一个或多个分量的电平增加。声音的总体电平在20分贝的范围内随机变化。报告了三个实验。在第一个实验中，我们确定了单频分量的调制如何影响该区域幅度变化的检测。在第二个实验中，信号是整个频谱的改变，并且该改变受到各种形式的调幅。在这两个实验中，调制通常都不会提高信号的可检测性。最后，在第三个实验中，我们确定了在不同相对相位下调制频谱的“信号”和“非信号”部分的效果。该实验结果表明，相对相位仅对低于约40赫兹的调制速率很重要。对于更快的速率，频谱的时间结构并不重要。因此，对于高于40赫兹的调制速率，只有刺激的功率谱是关键的。
