The mammalian cochlea is a sensory system with high sensitivity, sharp frequency selectivity and a broad dynamic range. These characteristics are due to the active nonlinear feedback by outer hair cells. Because it is an active nonlinear system, the cochlea sometimes emits spontaneous otoacoustic emissions (SOAEs) that are generated in the absence of any external stimulus due to the emergence of limit cycle oscillations. In this work, we use a computational physics-based model of the mammalian cochlea to investigate the generation of SOAEs. This model includes a three-dimensional model of the fluid mechanics in the cochlear ducts, a micromechanical model for the vibrations of the cochlear structures, and a realistic model of outer hair cell biophysics. Direct simulations of SOAEs in the time-domain demonstrate that the model is able to capture key experimental observations regarding SOAEs. Parametric studies and analysis of model simulations are used to demonstrate that SOAEs are a global phenomenon that arises due to the collective action of a distributed region of the cochlea rather than from spontaneous oscillations from individual outer hair cells.

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