ACOUSTIC STREAMING IN THE EAR ITSELF
ACOUSTIC STREAMING IN THE EAR ITSELF
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DOI：
10.1017/s0022112092004531
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发表时间：
1992-06-01
影响因子：
3.7
通讯作者：
LIGHTHILL, J
中科院分区：
文献类型：
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作者：
LIGHTHILL, J
正如通常被描述为声流的平均运动可以由声波产生，入射声波在充满液体的哺乳动物内耳中转换成的那些耳蜗行波也能够产生平均运动。对于每个频率ω的声学分量，这些在每单位长度的波能量E在急剧下降到零之前相当陡峭地上升到最大值E（max）的特征位置附近占主导地位。（最重要的是）通过耳蜗液内振动的基底膜刚度急剧且持续下降的分布，与普通声波的情况非常不同（分别参见截面符号2、3和4，用于在耳蜗横截面上和在边界层内沿沿着长度的能量分布），然而，对耳蜗中的平均流动运动的综合分析表明，它们受非常相似的规律支配。表达式1/4V 2C-1-3/4V（dV/dx）omega-1如Rayleigh（1896）针对边界层外的平均声流速度由于其中的波耗散而获得的，适合于在x方向上以速度幅度V（x）行进的波的（方程（1））仍然是良好的近似（参见截面符号5和6 -分别在低或高波数下进行一些适度的校正，在截面符号7和8中进行分析），用于耳蜗中的行波;然而，在特征位置附近，它们的相速度c降低到低值，与V的增加合谋，以增强那里的流动。远离附着在基底膜上的边界层，平均流动是作为与边界处的“有效滑移速度”分布（1）相一致的低雷诺数运动导出的（截面符号9）。该速度在特征位置处急剧下降到零（截面符号9和10），以产生平均体积流出量q=0.15E（最大）/rho（Ω-nu）1/2L（等式（160））每单位长度的基底膜进入中阶：在这里，rho和nu是内淋巴的密度和运动粘度（基本上，水的那些）并且L是基底膜刚度的e-折叠距离。这里导出的自由传播波（因此不允许任何行波放大的增强-在第3节中定性讨论-由于外毛细胞振动的强迫）是本文的主要结论。生理学上的问题是，这种流量q是否可以通过顶盖膜和内毛细胞之间的空间，因此，其静纤毛可能受到平均偏转力的刺激，在这里被指出，但推迟到以后的论文中详细考虑。
Just as mean motions, usually described as acoustic streaming, can be generated by sound waves, so also those cochlear travelling waves into which incident sound waves are converted in the liquid-filled mammalian inner ear are capable of generating mean motions. These predominate, for acoustic components of each frequency-omega, near the characteristic place where the wave energy E per unit length rises rather steeply to a maximum E(max) before dropping precipitously to zero.Even though the nature of cochlear travelling waves, as determined (above all) by the sharply and continuously falling distribution of stiffness for the basilar membrane vibrating within the cochlear fluids, is very different from that of ordinary sound waves (see sectional sign 2, 3 and 4 respectively for energy distribution along the length of the cochlea, over a cochlear cross-section and within boundary layers), nevertheless a comprehensive analysis of mean streaming motions in the cochlea shows them to be governed by remarkably similar laws. The expression 1/4V2C-1-3/4V(dV/dx)omega-1 (equation (1)) appropriate to a wave travelling in the x-direction with velocity amplitude V(x), as obtained by Rayleigh (1896) for the mean acoustic-streaming velocity just outside a boundary layer due to wave dissipation therein, remains a good approximation (see sectional sign 5 and 6 - with some modest corrections, at low or at high wavenumbers respectively, analysed in sectional sign 7 and 8) for travelling waves in the cochlea; where, however, the decrease of their phase velocity c to low values near the characteristic place conspires with the increase of V to enhance streaming there.Farther from the boundary layer attached to the basilar membrane, the mean streaming is derived (sectional sign 9) as a low-Reynolds-number motion compatible with the distribution (1) of 'effective slip velocity' at the boundary. This velocity's precipitous fall to zero at the characteristic place is shown (sectional sign 9 and 10) to produce there a mean volume outflow q=0.15E(max)/rho(omega-nu)1/2L (equation (160)) per unit length of the basilar membrane into the scala media: here, rho and nu are the endolymph's density and kinematic viscosity (essentially, those of water) and L is the e-folding distance for basilar-membrane stiffness.Equation (160), derived here for a freely propagating wave (and so not allowing for enhancements from any travelling-wave amplification - discussed qualitatively in sectional sign 3 - due to forcing by vibrations of outer hair cells) is the main conclusion of this paper. Physiological questions of whether this flow q may be channelled through the space between the tectorial membrane and inner hair cells, whose stereocilia may therefore be stimulated by a mean deflecting force, are noted here but postponed for detailed consideration in a later paper.