EVOKED OTOACOUSTIC EMISSIONS - NONLINEARITIES AND RESPONSE INTERPRETATION

Evoked otoacoustic emissions (EOAE's) are acoustic signals produced by the inner ear in response to transient acoustic stimuli and can be re corded in the external auditory canal. Since emissions can be reduced or even abolished by hearing losses of peripheral origin due to trauma and pathology, EOAE's are presently considered as the most sensitive clinical test for assessing the integrity of peripheral hearing. Recor dings of emissions evoked in response to transient stimuli are contami nated by an initial artifact which in most clinical environments can b e a very serious limitation. For this reason, a nonlinear estimation m ethod is widely used (derived nonlinear response, DNLR), instead of cl assical synchronous averaging. Aims of this paper are: i) to justify t heoretically the use of the DNLR technique by means of a simple model; ii) to compare the results obtained from the classical averaging (a l inear estimation technique) with those obtained from the nonlinear DNL R technique. Some suggestions of practical interest are finally inferr ed from present analysis.