Modeling dynamic properties of spontaneous otoacoustic emissions: Low-frequency biasing and entrainment

Abstract

Spontaneous otoacoustic emissions (SOAE) are sounds generated inside the living cochlea and are regarded as by-products of the active mechanism present in the peripheral auditory system. There is still debate whether these emissions are the product of local oscillators located at various positions along the cochlea (local oscillator model) or if they result from standing waves due to a global collective phenomenon that involves different aspects of the cochlea (global standing wave model). This paper uses a global standing wave cochlear model to predict various features of SOAEs. This involves a state-space formulation with a spatially distributed set of nonlinear active micromechanical elements coupled via cochlear fluid coupling. Simulation results have been compared with available experimental data and demonstrate two interesting nonlinear features of the cochlea: first, nonlinear properties of SOAEs modulated by external low-frequency bias tones are easily predicted and can be used to investigate the plausibility of different nonlinear functions incorporated in the micromechanical elements. Second, entrainment patterns can be obtained when the model is stimulated by a swept-tone: results show distinct areas of beating and others of entrainment between the external stimulus and the SOAE, which depend on the level and instantaneous frequency of the sweep.

Clusters in a Chain of Coupled Oscillators Behave Like a Single Oscillator: Relevance to Spontaneous Otoacoustic Emissions From Human Ears

“…A second model [35] has used an array of spatially disordered active nonlinear oscillators which are coupled both hydromechanically and visco-elastically; this approach finds that the oscillators also tend to cluster into frequency plateaus, with statistics resembling the actual cochlea. Most recently, a third approach has been to use a state-space model with a spatially distributed set of nonlinear active micromechanical elements coupled via the cochlear fluid, and has been able to predict various features of SOAEs [36].…”