Christopher A. Shera, PhD
|Title(s)||Professor of Otolaryngology-Head and Neck Surgery|
|Phone||+1 323 865 1685|
The peripheral auditory system transforms air-borne pressure waves into neural impulses that are interpreted by the brain as sound and speech. The cochlea of the inner ear is a snail-shaped electro-hydromechanical signal amplifier, frequency analyzer, and transducer with an astounding constellation of performance characteristics, including sensitivity to sub-atomic displacements with microsecond mechanical response times; wideband operation spanning three orders-of-magnitude in frequency; an input dynamic range of 120 dB, corresponding to a million-million-fold change in signal energy; useful operation even at signal powers 100 times smaller than the background noise; and ultra-low power consumption (15 µW). All of this is achieved not with the latest silicon technology or by exploiting the power of quantum computers — neither has yet approached the performance of the ear — but by self-maintaining biological tissue, most of which is salty water. How does the ear do it?
The Auditory Physics Group studies how the ear amplifies, analyzes, and creates sound. The goal is not only to understand how the cochlea achieves its astounding sensitivity and dynamic range but to use that knowledge to enhance the power of noninvasive probes of peripheral auditory function (e.g., otoacoustic emissions). Our approach involves a strong, quantitative interplay between theoretical modeling studies and physiological measurements. Ongoing work in the lab focuses on models of cochlear amplification, mechanisms of OAE generation, middle-ear transmission, and comparative studies of cochlear mechanics.