Possibilities for a Silicon Model of the Cochlea

Abstract

The purpose of this study is to resolve questions regarding the fundamental physical behavior of the cochlea of the inner ear. We seek a convergence of measurement and computation on physical models that capture essential features. Since there are unique features in the performance of the cochlea, the physical models could lead to device development. A much longer-term goal is a device for the assistance of hearing impaired individuals. The cochlea can be modeled as a tube of fluid divided by a partition, a portion of which is elastic and called the basilar membrane (BM). In preliminary work, the cochlear partition is constructed on a silicon wafer using current capabilities for micro-machining. The silicon nitride partition is inserted into a chamber of Plexiglas which is filled with solute and has a “stapes” for acoustic input and a “round window”. The silicon BM has the correct length, but is wider and isotropic. The measurements, supported by calculations, show that the deviation from the actual structure has a detrimental effect on the sharpness of the spatial distribution of the response for a fixed input frequency. Possibilities for improved models and for an active non-linear model with distributed sensors and actuators are discussed.