Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Department of Nuclear Chemistry, Břehová 7, 115 19 Prague 1, Czech Republic.
J Acoust Soc Am. 2012 May;131(5):3914-34. doi: 10.1121/1.3699207.
There is a long-lasting question of how distortion products (DPs) arising from nonlinear amplification processes in the cochlea are transmitted from their generation sites to the stapes. Two hypotheses have been proposed: (1) the slow-wave hypothesis whereby transmission is via the transverse pressure difference across the cochlear partition and (2) the fast-wave hypothesis proposing transmission via longitudinal compression waves. Ren with co-workers have addressed this topic experimentally by measuring the spatial vibration pattern of the basilar membrane (BM) in response to two tones of frequency f(1) and f(2). They interpreted the observed negative phase slopes of the stationary BM vibrations at the cubic distortion frequency f(DP) = 2f(1) - f(2) as evidence for the fast-wave hypothesis. Here, using a physically based model, it is shown that their phase data is actually in accordance with the slow-wave hypothesis. The analysis is based on a frequency-domain formulation of the two-dimensional motion equation of a nonlinear hydrodynamic cochlea model. Application of the analysis to their experimental data suggests that the measurement sites of negative phase slope were located at or apical to the DP generation sites. Therefore, current experimental and theoretical evidence supports the slow-wave hypothesis. Nevertheless, the analysis does not allow rejection of the fast-wave hypothesis.
关于耳蜗中非线性放大过程产生的失真产物 (DP) 如何从其产生部位传递到镫骨，存在一个长期存在的问题。提出了两种假设：(1) 慢波假说，即通过耳蜗隔板的横向压力差进行传输，以及 (2) 快波假说，提出通过纵向压缩波进行传输。Ren 及其同事通过测量基底膜 (BM) 对两个频率为 f(1) 和 f(2) 的音调的响应来实验性地解决了这个问题。他们将观察到的在立方失真频率 f(DP) = 2f(1) - f(2) 处的静止 BM 振动的负相斜率解释为支持快波假说的证据。在这里，使用基于物理的模型，表明他们的相位数据实际上与慢波假说一致。该分析基于非线性流体力学耳蜗模型的二维运动方程的频域公式。将分析应用于他们的实验数据表明，负相斜率的测量部位位于 DP 产生部位或其上方。因此，目前的实验和理论证据支持慢波假说。然而，该分析并不能排除快波假说。
