FEM Simulation Of Sound Transmission In Human Ear With Active Cochlear Model

Because of the complexity in human peripheral hearing system,varyinggeometry,varying material properties,the coupling between fluid and structure, it was verydifficult to capture the dynamic characteristic parameters of the middle ear and cochleaaccurately using the common numerical simulation method or combinedanalytical-numerical method. Finite element model including ear canal, middle ear with theligament and ossicular chain and simplified straight cochlea with an orthotropic basilarmembrane and dimensional material property variation along its length was established inthis thesis. Ansys harmonic analysis was done to analyze the cochlear responsecharacteristics under the sound stimuli from the ear canal. In the simulation many resultswere obtained, including the stapes footplate displacement on different conditions, basilarmembrane displacement along the length, the pressure of scala vestibuli, the curve offrequency selectivity characteristics. The results simulated were in consistent with theexperimental data, proving the validity of the integrated finite element model and could beexploited to simulate the sound transmission in human hearing system.The active cochlea included the amplification function of the Corti to the basilarmembrane vibration compared to the passive cochlea. The Corti was closely related with thehearing function. In the thesis the active cochlea was based on feed-forward mechanism andthe active force whose intensity was quantitated by the active amplification coefficient wasintroduced to the finite element model. The responses of the basilar membrane in activecochlea was analyzed under different sound stimulus levels. The nonlinear compression,frequency selectivity characteristics were obtained through the simulation and compared tothe passive cochlea. The simulation results in active cochlea showed that under lowstimulus level the active amplification was weak and vice versa and the amplification at theresonance point on the basilar membrane was predominant. The success in simulating theactive cochlea had fundamental significance in hearing diagnostics and study of otoacousticemission.