Modeling otoacoustic emissions by active nonlinear oscillators

The phenomenology of Spontaneous otoacoustic emissions (OAEs) is compared t o theoretical predictions given by models in which they are produced by act ive nonlinear oscillators. Along with the well-known Van der Pol oscillator , a new active oscillator model is proposed and analyzed here. Numerical si mulations and multi-scale analytical computation results are compared to ex perimental data of neonatal spontaneous and evoked OAEs. A simple analysis technique is proposed, in which the time evolution after a click stimulus o f the amplitude of each spectral line corresponding to a spontaneous OAE is studied. Apart from a few stationary lines, an approximately exponential d ecay law, with characteristic damping coefficients in the 20-200 Hz range, was found to fit the data. These results are not compatible with a Van der Pol oscillator model, and show that some important aspects of the OAE pheno menology can be better explained by the proposed oscillator. Other interest ing features of the spontaneous end evoked OAE phenomenology, such as spont aneous OAE suppression by external tones and the following recovery, as wel l as stimulus/response curves in the linear and nonlinear mode of acquisiti on, are also well reproduced by the proposed model. (C) 1999 Acoustical Soc iety of America. [S0001-4966(99)01310-7].