Alves-Pinto Ana, Lopez-Poveda Enrique A
Unidad de Audición Computacional y Psicoacústica, Instituto de Neurociencias de Castilla y León, Universidad de Salamanca, Avenida Alfonso X "El Sabio" s/n, 37007 Salamanca, Spain.
J Acoust Soc Am. 2008 Jul;124(1):409-21. doi: 10.1121/1.2920957.
To discriminate between broadband noises with and without a high-frequency spectral notch is more difficult at 70-80 dB sound pressure level than at lower or higher levels [Alves-Pinto, A. and Lopez-Poveda, E. A. (2005). "Detection of high-frequency spectral notches as a function of level," J. Acoust. Soc. Am. 118, 2458-2469]. One possible explanation is that the notch is less clearly represented internally at 70-80 dB SPL than at any other level. To test this hypothesis, forward-masking patterns were measured for flat-spectrum and notched noise maskers for masker levels of 50, 70, 80, and 90 dB SPL. Masking patterns were measured in two conditions: (1) fixing the masker-probe time interval at 2 ms and (2) varying the interval to achieve similar masked thresholds for different masker levels. The depth of the spectral notch remained approximately constant in the fixed-interval masking patterns and gradually decreased with increasing masker level in the variable-interval masking patterns. This difference probably reflects the effects of peripheral compression. These results are inconsistent with the nonmonotonic level-dependent performance in spectral discrimination. Assuming that a forward-masking pattern is a reasonable psychoacoustical correlate of the auditory-nerve rate-profile representation of the stimulus spectrum, these results undermine the common view that high-frequency spectral notches must be encoded in the rate-profile of auditory-nerve fibers.
在70 - 80分贝声压级下，区分具有和不具有高频频谱陷波的宽带噪声比在较低或较高声压级下更困难[阿尔维斯 - 平托，A. 和洛佩斯 - 波韦达，E. A.（2005年）。“高频频谱陷波的检测与声压级的关系”，《美国声学学会杂志》118，2458 - 2469]。一种可能的解释是，在70 - 80分贝声压级下，陷波在内部的表现不如在其他任何声压级下清晰。为了验证这一假设，测量了50、70、80和90分贝声压级的平坦频谱和带陷波噪声掩蔽器的前掩蔽模式。在两种条件下测量掩蔽模式：（1）将掩蔽器 - 探测时间间隔固定为2毫秒；（2）改变间隔以实现不同掩蔽器声压级下相似的掩蔽阈值。在固定间隔掩蔽模式中，频谱陷波的深度大致保持不变，而在可变间隔掩蔽模式中，随着掩蔽器声压级的增加，陷波深度逐渐减小。这种差异可能反映了外周压缩的影响。这些结果与频谱辨别中与声压级相关的非单调性能不一致。假设前掩蔽模式是刺激频谱的听神经速率分布表示的合理心理声学相关指标，这些结果削弱了高频频谱陷波必须在听神经纤维的速率分布中编码的普遍观点。
