Woodruff School of Mechanical Engineering
Faculty Candidate Seminar
Simulating the active nonlinear dynamics of the cochlea using a computational multi-physics model
Dr. Julien Meaud
University of Michigan, Ann Arbor
Wednesday, March 27, 2013 at 11:00:00 AM
MRDC Building, Room 4211
The mammalian ear is able to sense faint sounds (down to 0 dB SPL), distinguish between close frequencies (0.1% apart) and operate over a broad range of sound intensities (6 orders of magnitude). This striking performance is due to the presence of an active feedback mechanism linked to outer hair cell activity in the sensory organ of the inner ear, the cochlea. Thanks to this feedback mechanism, called cochlear amplifier, the cochlea is a nonlinear system that exhibits high sensitivity and sharp tuning in response to low level sounds and a broad dynamic range. Failure of the cochlear amplifier due to diseases, ototoxic drugs, sound overexposure or aging causes deafness or hearing loss. Better understanding of how the cochlea processes sounds is needed to better protect hearing, diagnose hearing pathologies and treat hearing loss. Development of computational models of the cochlea allows testing theories of active cochlear mechanics and could have both scientific and clinical applications. In this talk I will present a nonlinear multi-physics model of the cochlea. This computational model, formulated in the frequency domain using an alternating frequency/time method, couples the mechanical, electrical and acoustical domains of the cochlea using finite element methods and includes detailed models for the biophysics of outer hair cells. I will demonstrate that this physically-motivated model is able to simulate the main aspects of the nonlinear response of the cochlea to single-tone and two-tone stimuli. Finally, I will show that the model can be used as a virtual laboratory that can test for example the effect of genetic mutations on cochlear tuning.
Julien Meaud is currently a Research Fellow in the Vibrations and Acoustics Laboratory in the Department of Mechanical Engineering at the University of Michigan, Ann Arbor, where he works on computational cochlear mechanics under the supervision of Prof. Karl Grosh. He studied engineering as an undergraduate at the Ecole Centrale de Lyon in France. He received a Master of Science in 2006 and a Ph. D. in Mechanical Engineering in 2010, both from the University of Michigan. His work on cochlear mechanics has been published in the major journals of acoustical and biophysical research. He was awarded a best student paper award at the 2009 Acoustical Society Meeting for a presentation of his computational model of the cochlea. Prior to his current postdoctoral appointment, he worked with Prof. Gregory Hulbert as a Research Fellow in the Computational Mechanics Laboratory at the University of Michigan and investigated the mechanics and design of composite materials with high stiffness and high damping in response to dynamic loads.
Refreshments will be served.