Human Communication and Deafness Division, University of Manchester, Manchester M13 9PL, United Kingdom.
J Acoust Soc Am. 2010 Aug;128(2):771-86. doi: 10.1121/1.3455844.
On- and off-frequency compression at the 4000- and 8000-Hz cochlear places were estimated using a new version of the additivity of forward masking (AFM) technique, that measures the effects of combining two non-overlapping forward maskers. Instead of measuring signal thresholds to estimate compression of the signal as in the original AFM technique, the decrease in masker threshold in the combined-masker condition compared to the individual-masker conditions is used to estimate compression of the masker at the signal place. By varying masker frequency it is possible to estimate off-frequency compression. The maskers were 500-Hz-wide bands of noise, and the signal was a brief pure tone. Compression at different levels was estimated using different overall signal levels, or different masker-signal intervals. It was shown that the new AFM technique and the original AFM technique produce consistent results. Considerable compression was observed for maskers well below the signal frequency, suggesting that the assumption of off-frequency linearity used in other techniques may not be valid. Reducing the duration of the first masker from 200 to 20 ms reduced the compression exponent in some cases, suggesting a possible influence of olivocochlear efferent activity.
在 4000Hz 和 8000Hz 的耳蜗位置上，使用一种新的前向掩蔽叠加性（AFM）技术来估计加性和减性频率压缩，该技术可测量两个不重叠的前向掩蔽器组合的效果。与原始 AFM 技术中测量信号阈值以估计信号压缩不同，使用组合掩蔽器条件下掩蔽器阈值的降低与单独掩蔽器条件下的阈值降低来估计信号位置掩蔽器的压缩。通过改变掩蔽器频率，可以估计非频率压缩。掩蔽器是 500Hz 宽的噪声带，信号是短暂的纯音。使用不同的总信号水平或不同的掩蔽器-信号间隔来估计不同水平的压缩。结果表明，新的 AFM 技术和原始的 AFM 技术产生了一致的结果。对于低于信号频率的掩蔽器，观察到了相当大的压缩，这表明其他技术中使用的非频率线性假设可能不成立。在某些情况下，将第一个掩蔽器的持续时间从 200 毫秒减少到 20 毫秒，降低了压缩指数，这表明可能奥利弗耳蜗传出活动的影响。
