Signal processing in the auditory periphery : relation to the cochlear delay

发音同步是将声音知觉归类为单一音调的重要线索。然而，即使单一复杂音调的所有成分在物理上完全同时开始，它们的时间关系可能也不会在耳蜗处得到保留。耳蜗基底膜(BM)的硬度从基底侧(更靠近椭圆形窗)向顶侧逐渐减小。因此，低频分量引起的振动比高频分量引起的振动到达其关联位置的时间更晚。这种现象被称为“耳蜗延时”。我们进行了一系列的声学和生理学实验，以研究耳蜗延时是否显著影响同步性的知觉判断，以及听觉脑干反应(ABR)是否会相应地改变。本研究采用两种不同类型的啁啾作为实验刺激，分别控制耳蜗延迟量和脉冲，以考察耳蜗延迟量是否会对两个声音的知觉同步性判断产生系统性偏差。心理声学实验的结果表明，同步判断的准确率最高的刺激是内源性的耳蜗延时(脉冲)。此外，引起增强的耳蜗延时的刺激比抵消耳蜗延时的刺激的准确率更高。生理实验结果表明，人的听觉系统存在时间加工的非对称性；心理声学实验结果表明，对于引起固有的耳蜗延时(脉冲)的刺激，同步判断准确率最高。此外，引起增强的耳蜗延时的刺激比抵消耳蜗延时的刺激的准确率更高。生理实验的结果表明，人类听觉系统中存在时间加工的不对称方面。

Onset synchrony is an important cue for perceptual grouping of sounds as a single tone. However, even if all of the components of a single complex tone physically begin exactly simultaneously, their temporal relation might not be preserved at the cochlear level. The stiffness of the cochlear Basilar Membrane(BM) gradually decreases from the basal side(closer to the oval window) to the apical side. Therefore, the vibration caused by low-frequency components reaches its associated location later than that caused by high-frequency components. This phenomenon is referred to as "cochlear delay." We have performed a series of phychoacoustic and physiological experiments to investigate if the cochlear delay significantly affects the perceptual judgment of synchronization, and also if Auditory Brainstem Response(ABR) would change accordingly. Two types of chirps which were controlled the amount of cochlear delay and a pulse were used as experimental stimuli to investigate whether or not cochlear delay imposes a systematic bias on the judgment of perceptual synchrony of two sounds. The results of the psychoacoustic experiments showed that the synchrony judgment accuracy was highest for stimuli that evoke an intrinsic cochlear delay(pulse). Furthermore, accuracy was higher for stimuli that evoke enhanced cochlear delay than for stimuli that cancelled out cochlear delay. The results of the physiological experiments showed that there is an asymmetric aspect of temporal processing in the human auditory system.The results of the psychoacoustic experiments showed that the synchrony judgment accuracy was highest for stimuli that evoke an intrinsic cochlear delay(pulse). Furthermore, accuracy was higher for stimuli that evoke enhanced cochlear delay than for stimuli that cancelled out cochlear delay. The results of the physiological experiments showed that there is an asymmetric aspect of temporal processing in the human auditory system.