Nonlinear dynamics of spontaneous otoacoustic emissions in the presence of internal noise in models of the inner ear

Abstract

Spontaneous otoacoustic emissions (SOAEs) are sounds generated by the inner ear in the absence of an external stimulus and are a direct consequence of the inner ear nonlinearity that arises from hair cell electromechanics. SOAEs with similar spectral characteristics have been observed in both mammals and non-mammalian species such as lizards, suggesting a common mechanism in their generation, despite striking differences in inner ear physiology between mammals and non-mammals. In this work, a model based on coupled limit-cycle oscillators (Vilfan and Duke, Biophys. J, vol. 95, pp. 4622–4630, 2008) and a model based on standing waves (Bowling etal., Sci. Rep., vol. 11, pp. 1–14, 2021) are implemented to analyze their ability to predict key SOAE characteristics. As in experiments, the models predict discrete peaks in the SOAEs with quasi-periodic spacing. However, if noise is neglected, the SOAE peaks are unrealistically sharp. In this work, the effect of noise on SOAE spectral properties (e.g., bandwidth of SOAE peaks) and statistical properties (e.g., interpeak cross-correlations) is evaluated to assess whether either model is a better representation of SOAE generation. This is a key step in understanding the theoretical underpinnings of SOAE generation. [Research funded by NIH grant R01 DC016114.]