Department of Experimental Audiology, Otto-von-Guericke University of Magdeburg, Magdeburg, Germany.
Adv Exp Med Biol. 2013;787:475-82. doi: 10.1007/978-1-4614-1590-9_52.
A common characteristic of natural sounds is that the level fluctuations in different frequency regions are coherent. The ability of the auditory system to use this comodulation is shown when a sinusoidal signal is masked by a masker centred at the signal frequency (on-frequency masker, OFM) and one or more off-frequency components, commonly referred to as flanking bands (FBs). In general, the threshold of the signal masked by comodulated masker components is lower than when masked by masker components with uncorrelated envelopes or in the presence of the OFM only. This effect is commonly referred to as comodulation masking release (CMR). The present study investigates if CMR is also observed for a sinusoidal signal embedded in the OFM when the centre frequencies of the FBs are swept over time with a sweep rate of one octave per second. Both a common change of different frequencies and comodulation could serve as cues to indicate which of the stimulus components originate from one source. If the common fate of frequency components is the stronger binding cue, the sweeping FBs and the OFM with a fixed centre frequency should no longer form one auditory object and the CMR should be abolished. However, psychoacoustical results with normal-hearing listeners show that a CMR is also observed with sweeping components. The results are consistent with the hypothesis of wideband inhibition as the underlying physiological mechanism, as the CMR should only depend on the spectral position of the flanking bands relative to the inhibitory areas (as seen in physiological recordings using stationary flanking bands). Preliminary physiological results in the cochlear nucleus of the Guinea pig show that a correlate of CMR can also be found at this level of the auditory pathway with sweeping flanking bands.
自然声音的一个共同特征是不同频率区域的电平波动具有相干性。当正弦信号被中心频率位于信号频率（同频掩蔽，OFM）处的掩蔽器以及一个或多个离频分量（通常称为侧翼带，FBs）掩蔽时，听觉系统利用这种调制的能力就会表现出来。一般来说，被调制掩蔽器分量掩蔽的信号的阈值低于被具有不相关包络的掩蔽器分量掩蔽的情况，或者仅存在 OFM 的情况。这种效应通常被称为调制掩蔽释放（CMR）。本研究考察了当 FBs 的中心频率随每秒一个八度的扫频速率变化时，是否也会观察到嵌入 OFM 中的正弦信号的 CMR。不同频率的常见变化和调制都可以作为提示，指示刺激组件中的哪一个来自一个源。如果频率分量的共同命运是更强的绑定提示，那么扫频 FBs 和具有固定中心频率的 OFM 不应再形成一个听觉对象，并且 CMR 应该被取消。然而，正常听力听众的心理物理结果表明，即使使用扫频分量，也可以观察到 CMR。结果与宽带抑制作为潜在生理机制的假设一致，因为 CMR 应该只取决于侧翼带的频谱位置相对于抑制区域的位置（如使用固定侧翼带的生理记录中所见）。豚鼠耳蜗核的初步生理结果表明，在听觉通路的这一水平上，也可以用扫频侧翼带找到 CMR 的相关物。
