Cochlear reflectivity in transmission-line models and otoacoustic emission characteristic time delays.

In transmission-line models of cochlear mechanics, predictions about otoacoustic-emission delays depend on the place- or wave-fixed nature of the emission generation mechanism. In this work, transient evoked otoacoustic emissions (TEOAEs), recorded at different stimulus levels in 10 young subjects, were analyzed using wavelet-based time-frequency analysis to determine the latency of each frequency component of the response. The same wave forms were Fourier analyzed to evaluate the phase-gradient delay as a function of frequency. Interpreting the relation between these two characteristic delays using cochlear models shows that most of the TEOAE response can be attributed to place-fixed reflection mechanisms. The causality principle explains observed correlations between fluctuations of the TEOAE amplitude and phase-gradient delay.