Bacon S P
Department of Speech and Hearing Science, Arizona State University, Tempe 85287-0102.
J Acoust Soc Am. 1990 Aug;88(2):698-702. doi: 10.1121/1.399773.
Overshoot refers to the phenomenon where signal detectability improves for a short-duration signal as the onset of that signal is delayed relative to the onset of a longer duration masker. A popular explanation for overshoot is that it reflects short-term adaptation in auditory-nerve fibers. In this study, overshoot was measured for a 10-ms, 4-kHz signal masked by a broadband noise. In the first experiment, masker duration was 400 ms and signal onset delay was 1 or 195 ms; masker spectrum level ranged from - 10-50 dB SPL. Overshoot was negligible at the lowest masker levels, grew to about 10-15 dB at the moderate masker levels, but declined and approached 0 dB at the highest masker levels. In the second experiment, the masker duration was reduced to 100 ms, and the signal was presented with a delay of 1 or 70 ms; masker spectrum level was 10, 30, or 50 dB SPL. Overshoot was about 10 dB for the two lower masker levels, but about 0 dB at the highest masker level. The results from the second experiment suggest that the decline in overshoot at high masker levels is probably not due to auditory fatigue. It is suggested, instead, that the decline may be attributable to the neural response at high levels being dominated by those auditory-nerve fibers that do not exhibit short-term adaptation (i.e., those with low spontaneous rates and high thresholds).
当一个短持续时间信号的起始相对于一个长持续时间掩蔽音的起始延迟时，该信号的可检测性会提高。对过冲的一种普遍解释是，它反映了听神经纤维中的短期适应。在本研究中，测量了被宽带噪声掩蔽的10毫秒、4千赫兹信号的过冲。在第一个实验中，掩蔽音持续时间为400毫秒，信号起始延迟为1或195毫秒；掩蔽音频谱水平范围为-10至50分贝声压级。在最低掩蔽音水平下，过冲可忽略不计，在中等掩蔽音水平下增长到约10至15分贝，但在最高掩蔽音水平下下降并接近0分贝。在第二个实验中，掩蔽音持续时间缩短至100毫秒，信号以1或70毫秒的延迟呈现；掩蔽音频谱水平为10、30或50分贝声压级。对于两个较低的掩蔽音水平，过冲约为10分贝，但在最高掩蔽音水平下约为0分贝。第二个实验的结果表明，在高掩蔽音水平下过冲的下降可能不是由于听觉疲劳。相反，有人认为这种下降可能归因于高水平的神经反应由那些不表现出短期适应的听神经纤维主导（即那些自发率低和阈值高的纤维）。
