WAVELET ANALYSIS OF CLICK-EVOKED OTOACOUSTIC EMISSIONS

Time-frequency distribution methods are being widely used for the anal ysis of a variety of biomedical signals. Recently, they have been appl ied also to study otoacoustic emissions (OAE's), the active acoustic r esponse of the hearing end organ. Click-evoked otoacoustic emissions ( CEOAE's) are time-varying signals with a clear frequency dispersion al ong with the time axis. Analysis of CEOAE's is of considerable interes t due to their close relation with cochlear mechanisms. In this paper, several basic time-frequency distribution methods are considered and compared on the basis of both simulated signals and real CEOAE's. The particular structure of CEOAE's requires a method with both a satisfac tory time and frequency resolution. Results from simulations and real CEOAE's revealed that the wavelet approach is highly suitable for the analysis of such signals. Some examples of the application of the wave let transform to CEOAE's are provided here, Applications range from th e extraction of normative data from adult and neonatal OAE's to the ex traction of quantitative parameters for clinical purposes.