Plack Christopher J, Drga Vit
Department of Psychology, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, England.
J Acoust Soc Am. 2003 Mar;113(3):1574-86. doi: 10.1121/1.1538247.
Psychophysical estimates of compression often assume that the basilar-membrane response to frequencies well below characteristic frequency (CF) is linear. Two techniques for estimating compression are described here that do not depend on this assumption at low CFs. In experiment 1, growth of forward masking was measured for both on- and off-frequency pure-tone maskers for pure-tone signals at 250, 500, and 4000 Hz. The on- and off-frequency masking functions at 250 and 500 Hz were just as shallow as the on-frequency masking function at 4000 Hz. In experiment 2, the forward masker level required to mask a fixed low-level signal was measured as a function of the masker-signal interval. The slopes of these functions did not differ between signal frequencies of 250 and 4000 Hz for the on-frequency maskers. At 250 Hz, the slope for the 150-Hz masker was almost as steep as that for the on-frequency masker, whereas at 4000 Hz the slope for the 2400-Hz masker was much shallower than that for the on-frequency masker. The results suggest that there is substantial compression, of around 0.2-0.3 dB/dB, at low CFs in the human auditory system. Furthermore, the results suggest that at low CFs compression does not vary greatly with stimulation frequency relative to CF.
压缩的心理物理学估计通常假定基底膜对远低于特征频率（CF）的频率的响应是线性的。这里描述了两种估计压缩的技术，它们在低CF时不依赖于这一假设。在实验1中，测量了250、500和4000Hz纯音信号的同频和异频纯音掩蔽器的前掩蔽增长情况。250和500Hz的同频和异频掩蔽函数与4000Hz的同频掩蔽函数一样浅。在实验2中，测量了掩蔽固定低电平信号所需的前掩蔽器电平作为掩蔽器 - 信号间隔的函数。对于同频掩蔽器，250和4000Hz信号频率之间这些函数的斜率没有差异。在250Hz时，150Hz掩蔽器的斜率几乎与同频掩蔽器的斜率一样陡，而在4000Hz时，2400Hz掩蔽器的斜率比同频掩蔽器的斜率浅得多。结果表明，在人类听觉系统的低CF时存在约0.2 - 0.3dB/dB的显著压缩。此外，结果表明在低CF时，相对于CF，压缩随刺激频率的变化不大。
