Passive and active structural acoustic filtering in cochlear mechanics: Analysis and applications

A linear physiologically-based finite element model is developed for analyzing the global mechanical-electrical-acoustic (active) filtering in the mammalian cochlea. The model consists of a two-duct fluid-filled rectangular geometry, the micro-mechanical structural network interacting with the fluid, electrical circuit equivalent of cells and fluid in every cross-section connected by longitudinal cables representing the conductivity of the cochlear fluids and includes the mechano-electrical and electro-mechanical transduction at the outer hair cells. The acoustic pressures, structural displacements, and electrical potentials are determined numerically and compared with experiments. For the first time, the response of the cochlea to both acoustic and electrical excitation are predicted using the same physiological model and compared with experiments.; Reducing the amount of activity present in the model reduces the gain and lowers the frequency of peak BM velocity response compared to a fully active model, in accordance with experimental data. This model also possesses near invariance to click induced noise at different gain levels. Using the same model parameters, the predictions of the local BM velocity response to electrical stimulation match available experimental data, providing an independent test of the model capability. Predictions of electrically evoked otoacoustic emissions are found to match experimental results as well. Roughness introduced into BM stiffness is found to result in fine structures in a fully-active model and have little effect on a model with reduced activity.; A new kind of passive hydraulic and pneumatic silencer called the structural acoustic silencer for broadband passive noise control is designed based on analogy with passive mechanics of the cochlea and compared with physical tests from experiments. The design of the silencer is done numerically using three dimensional finite element method. The structural acoustic silencers indeed result in broadband transmission loss. The relation between transmission loss and plate dispersion in the silencer is shown for the first time.