Investigating the Emission of Sounds by the Mammalian Ear Using a Computational Model

Georgia Tech Research Corporation, Atlanta GA

Investigators

Abstract

The function of the mammalian inner ear is to detect sounds. However, the inner ear is not just a sensory system; it can also emit sounds that can be measured by placing a microphone in the ear canal. These sounds, called otoacoustic emissions, are commonly used to obtain indirect information about inner ear function. Because of the noninvasive and low-cost nature of otoacoustic emission measurements, otoacoustic emissions have not only scientific applications but also clinical applications such as newborn hearing screening tests. Unfortunately, many aspects of otoacoustic emissions are still poorly understood, which limits how much information can be obtained from these measurements. This project aims to develop a clear understanding of mammalian otoacoustic emissions. The results from this fundamental research will help to improve hearing screening tests, auditory prostheses and cochlear implants. Hence this project could have a tremendous societal impact since about 50 million Americans suffer from some level of hearing loss. Additionally, the knowledge gained from this research about hearing biomechanics will help to design novel sensors that mimic the function of the inner ear. This award will support the interdisciplinary training of graduate students in biomechanics, biophysics, acoustics and computational modeling. This research will involve participation of women and students from underrepresented groups and will be disseminated to a broader audience. This research will focus on a specific type of otoacoustic emissions, called distortion product otoacoustic emissions. Distortion product otoacoustic emissions are emitted in response to a two-tone stimulus due to the nonlinearity of the inner ear. Current experiments and models are unable to conclusively establish the precise site of generation of distortion product otoacoustic emissions. Furthermore, several hypotheses exist regarding the primary path for the propagation of distortion product otoacoustic emission from their site of generation to the ear canal. To address these questions, this research will use physiologically-based computational models of the mammalian ear that include key features not included in other models of otoacoustic emissions. These models couple a lumped parameter model of the middle ear to three-dimensional finite element models of the inner ear. Numerical simulations will be used to determine where otoacoustic emissions are generated and how they propagate from their site of generation to the ear canal. These theoretical results will be validated and tested by comparison to experimental data provided by collaborators.