Speaker
Description
Healthy hearing relies on the careful orchestration and strong coupling of the mechanical, electrical, and fluidic domains in the mammalian cochlea. There is a dearth of data and simulation results for a broad swath of the cochlea including the apex, a region responsible for processing speech frequencies. With the advent of vibrometry based on optical coherence tomography and signal processing techniques, it is now possible to measure the sound-evoked response of intracochlear structures at the apex without opening the cochlear capsule. The experimental data available to date suggest that the apex functions differently from the oft-studied cochlear base, but there is significant disagreement amongst different groups’ measurements. We analyze the cochlear response to sound using a combination of time-domain and frequency-domain algorithms for predicting the nonlinear electro-fluidic-structural response providing mechanistic insights not possible through experiments. We show how different optical axes of measurement can give rise to dramatically different results, explaining some variations in measured responses. We find that the transition to the broadly tuned low-frequency response region arises due to the combination of geometric changes, frequency regimes, and viscous fluid-structure interaction at the apex. Moreover, experiments and theory for transient responses at the lowest frequencies sensed in the cochlea show peak locations that do not correlate with the standard place-frequency mapping. These results have practical implications for the design of auditory prosthesis and algorithms for hearing restoration.