Department of Neuroscience, Erasmus MC, P.O. Box 2040, 3000 CA, Rotterdam, The Netherlands.
J Assoc Res Otolaryngol. 2012 Dec;13(6):785-98. doi: 10.1007/s10162-012-0345-0. Epub 2012 Aug 31.
The mammalian inner ear combines spectral analysis of sound with multiband dynamic compression. Cochlear mechanics has mainly been studied using single-tone and tone-pair stimulation. Most natural sounds, however, have wideband spectra. Because the cochlea is strongly nonlinear, wideband responses cannot be predicted by simply adding single-tone responses. We measured responses of the gerbil basilar membrane to single-tone and wideband stimuli and compared them, while focusing on nonlinear aspects of the response. In agreement with previous work, we found that frequency selectivity and its dependence on stimulus intensity were very similar between single-tone and wideband responses. The main difference was a constant shift in effective sound intensity, which was well predicted by a simple gain control scheme. We found expansive nonlinearities in low-frequency responses, which, with increasing frequency, gradually turned into the more familiar compressive nonlinearities. The overall power of distortion products was at least 13 dB below the overall power of the linear response, but in a limited band above the characteristic frequency, the power of distortion products often exceeded the linear response. Our results explain the partial success of a "quasilinear" description of wideband basilar membrane responses, but also indicate its limitations.
哺乳动物的内耳将声音的频谱分析与多频带动态压缩相结合。耳蜗力学主要通过单音和双音刺激来研究。然而，大多数自然声音都具有宽带频谱。由于耳蜗具有很强的非线性，因此不能通过简单地叠加单音响应来预测宽带响应。我们测量了沙鼠的基底膜对单音和宽带刺激的反应，并进行了比较，同时重点关注了反应的非线性方面。与以前的工作一致，我们发现单音和宽带响应之间的频率选择性及其对刺激强度的依赖性非常相似。主要的区别是有效声音强度的恒定偏移，这可以通过一个简单的增益控制方案很好地预测。我们发现低频响应中存在扩张性的非线性，随着频率的增加，这种非线性逐渐转变为更为熟悉的压缩性非线性。失真产物的总功率至少比线性响应低 13 分贝，但在特征频率以上的一个有限带宽内，失真产物的功率常常超过线性响应。我们的结果解释了宽带基底膜响应的“准线性”描述的部分成功，但也表明了其局限性。
