Transient-evoked otoacoustic emission generators in a nonlinear cochlea

This study focuses on the theoretical prediction and experimental evaluation of the latency of transient-evoked otoacoustic emissions. Response components with different delay have been identified in several studies. The main generator of the transient response is assumed to be coherent reflection from cochlear roughness near the resonant place. Additional components of different latency can be generated either by reflection from cochlear regions between the base and the resonant place, or by intermodulation distortion of higher-frequency tones, or by multiple intra-cochlear reflections. Experimental data are re-analyzed in this study to evaluate the dependence of the latency on stimulus level, for each component of the response. This analysis shows that previous estimates of the otoacoustic emission latency and of its dependence on stimulus level were affected by systematic errors. The latency of the emission from each generator changes very little with stimulus level, whereas their different growth rate causes sharp changes of the single-valued latency, estimated as the time of the absolute maximum of the band-pass filtered transient-evoked response. A passive linear model and an active linear model including delayed stiffness terms are used to predict the latency of the different components, and these predictions are compared with the experimental data.