Ph.D. Proposal Presentation by Charlotte Kotas
Tuesday, November 29, 2005

(Dr. Minami Yoda, Chair)

"Acoustically Induced Fluid Flows in a Model Fish Ear"


Acoustically induced flows in the fluid (endolymph) of the inner ear create steady flow in the ear due to nonlinear effects.  This so-called steady or acoustic streaming is capable of generating complex flow patterns in the ear that contain information about the frequency, amplitude and direction of the incident sound.  The auditory retina hypothesis suggests that such flow patterns are sensed by an array of hair cells in the ear, much like how photoreceptors on the (visual) retina sense patterns of light.
The objective of this doctoral research is therefore to characterize the periodic and steady flow patterns associated with oscillating model otolith geometries, including spheres as well as oblate and prolate spheroids.  Flow visualization and particle-image velocimetry (PIV) will be used to study the flow around model otoliths immersed in various liquids oscillated at various frequencies and with various amplitudes to study how characteristics of the incident sound affect such flow patterns.  The oscillation direction will be varied to assess how the direction of incoming sound affects the flow patterns.  The results of this work should lead to new compact underwater acoustic sensor designs and an improved understanding of how fish detect and directionalize underwater sound.