Robles L, Ruggero M A, Rich N C
Department of Otolaryngology, University of Minnesota, Minneapolis 55414.
Nature. 1991 Jan 31;349(6308):413-4. doi: 10.1038/349413a0.
When humans listen to pairs of thnes they hear additional tones, or distortion products, that are not present in the stimulus. Two-tone distortion products are also known as combination tones, because their pitches match combinations of the primary frequencies (f1 and f2, f2 greater than f1), such as f2-f1, (n + 1)f1-nf2 and (n + 1)f2-nf1 (n = 1, 2, 3...). Physiological correlates of the perceived distortion products exist in responses of auditory-nerve fibres and inner hair cells and in otoacoustic emissions (sounds generated by the cochlea, recordable at the ear canal). Because the middle ear responds linearly to sound and neural responses to distortion products can be abolished by damage to hair cells at cochlear sites preferentially tuned to the frequencies of the primary tones, it was hypothesized that distortion products are generated at these sites and propagate mechanically along the basilar membrane to the location tuned to the distortion-product frequency. But until now, efforts to confirm this hypothesis have failed. Here we report the use of a new laser-velocimetry technique to demonstrate two-tone distortion in basilar-membrane motion at low and moderate stimulus intensities.
当人类聆听成对的纯音时，他们会听到刺激中不存在的额外音调或失真产物。双音失真产物也被称为组合音调，因为它们的音高与基频（f1和f2，f2大于f1）的组合相匹配，例如f2 - f1、（n + 1）f1 - nf2和（n + 1）f2 - nf1（n = 1, 2, 3...）。感知到的失真产物的生理相关物存在于听神经纤维和内毛细胞的反应以及耳声发射（由耳蜗产生、可在耳道记录的声音）中。由于中耳对声音呈线性反应，并且对失真产物的神经反应可因优先调谐到基频的耳蜗部位的毛细胞受损而消除，因此有人推测失真产物在这些部位产生，并沿基底膜机械地传播到调谐到失真产物频率的位置。但直到现在，证实这一假设的努力都失败了。在此我们报告使用一种新的激光测速技术来证明在低和中等刺激强度下基底膜运动中的双音失真。
