Wavelet-type analysis of transient-evoked otoacoustic emissions

A transient-evoked otoacoustic emission (TEOAE) is a sound originating in the cochlea in response to a brief acoustic stimulus, such as a click. The response is typically a weak (25 dB SPL maximum) signal that lasts 20-40 ms. Analysis of TEOAEs is promising as a noninvasive technique for understanding cochlear function and as a diagnostic tool in identifying hearing loss. A TEOAE database was collected on many subjects, some of which were administered quinine to study the effect of the drug on TEOAE. Historically, FFT techniques have not worked well on TEOAE data because of the nonstationary nature of the signals. We have used a wavelet-like approach in analyzing the data by employing a set of equal-bandwidth filters, which have revealed the emission energy to be concentrated in the 800-2000 Hz range. This type of analysis is shown to be useful in examining the time progression of different frequency bands of the click-evoked emissions in subjects who took quinine.