Time-frequency Distributions of Click-evoked Otoacoustic Emissions

Emissions evoked by broad-band stimuli, such as clicks, show a 'frequency dispersion' reminiscent of the place-frequency distribution along the cochlea. Analysis of the time-frequency properties of transiently evoked otoacoustic emissions (TEOAEs) is therefore of considerable interest due to their close relation with cochlear mechanisms. In particular, since OAEs in response to click stimuli are expected to evoke a cumulative response from the whole cochlea, the analysis of click-evoked OAEs can yield a global view of cochlear function. Wavelet analysis is performed to obtain time-frequency distributions of click-evoked OAEs at various intensity levels from normal ears. By means of the inverse wavelet transform, the recorded responses are decomposed into elementary components representing the contribution within a narrow frequency band to the cumulative OAE. The relationship between the frequency of the elementary components, latency and level of stimulation is described.