An analog electronic cochlea

Absfracf-An engineered system that hears, such as a speech recognizer, can be designed by modeling the cochlea, or inner ear, and higher levels of the auditory nervous system. To he useful in such a system, a model of the cochlea should incorporate a variety of known effects, such as an asymmetric low-passibandpass response at each output channel, a short ringing time, and active adaptation to a wide range of input signal levels. An analog electronic cochlea has been built in CXIOS VLSI technology using micropower techniques to achieie this goal of usefulness via realism. The key point of the model and circuit is that a cascade of simple, near13 linear, second-order filter stages with controllable Q parameters suffices to capture the physics of the fluid-d>namic traveling-wave sjstem in the cochlea. including the effects of adaptation and active gain involving the outer hair cells. hleasurements on the test chip suggest that the circuit matches hoth the theory and observations from real cochleas.