Cochlear wave propagation and micromechanics

Richard Chadwick
National Institute of Health

I will describe our current status of cochlear mechanics modeling using a hybrid analytical/computational approach that incorporates slowly varying asymptotics used in conjunction with finite-elements. The method uses an iterative algorithm to solve a complex fluid-solid interaction problem in a realistic cross section of the cochlea, for the axial wavenumber and fluid-solid modes at a specified frequency and axial location. The computations are carried out using the MATLAB p.d.e. Toolbox. The model treats the basilar membrane as an anisotropic plate, and the Organ of Corti and tectorial membrane as inhomogeneous elastic domains. Elastic coupling of the tectorial membrane to the reticular lamina is included via outer hair cell stereocilia. We have obtained some interesting results that elucidate the role of tectorial membrane radial motion and cochlear curvature in improving the shear gain at the hair bundles. Also, we have obtained more complete analytic results on a simplified model that cochlear curvature could amplify low-frequency waves reaching the apex of some cochleae by as much as 20 dB.

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