SUMMARY

The mammalian ear is a complex biological system that can detect sound signals and amplify the response to low-level sounds, driven by electromotility of outer hair cells (OHCs). This research focus on two distinct aspects of cochlear mechanics. The first contribution of this research is related to distortion product otoacoustic emissions (DPOAEs), a sound signal that can be detected in the ear canal in response to two-tone stimulus. DPOAE measurement often serves as a noninvasive approach to probe cochlear function in clinical applications. This research aims to clarify the generation and propagation mechanism of intracochlear DP. In the preliminary research, a physiologically-motivated gerbil cochlear model with electrical longitudinal coupling was calibrated to capture the nonlinear measurement in extracellular OHC voltage. The model was then used to interpret DP results to clarify the mechanisms of distortion product generation by OHCs. The second aspect of the research focus on the influence of genetic mutations on material properties of mouse tectorial membrane (TM), which is an extracellular matrix located above OHCs. This research aims to study the relationship between genetic mutations and loss of normal cochlear function by examining the material properties of TM in wild-type and transgenic mice. During the preliminary research, a computational TM model with viscous boundary layer was employed to determine the effect of genetic mutation on material properties of the mouse TM by using an inverse fitting methodology. The proposed research will focus on three aspects: 1. Implement a nonlinear frequency domain model to significantly improve the speed of simulation. 2. Examine how the primary frequency ratio on the generation and propagation of DP. 3. Analyze the effect of genetic mutation on TM material properties by using wave propagation measurement.