Application of Informations of DPOAE Phase

Abstract

Phase informations of distortion product otoacoustic emission (DPOAE) has been used for calculation of the latency of DPOAE generation, however this measurement is not clinically applied. We invented a novel clinical application of the DPOAE phase information, and propose an idea of utilizing the DPOAE phase for predicting the phase of basilar membrane vibration. The traveling wave is known to show a phase-nonlinearity that the phase lags to increasing stimulus when the stimulus frequency is below the best frequency, while the phase gains when the stimulus frequency is above the best frequency. We found out a similar nonlinear characteristic in the relation between the intensity of lower stimulus tone (L1) and 2f1-f2 DPOAE phase. In seven normal hearing volunteers, the phases lagged to L1 increase when f2/f1 ratio was above 1.22, whereas the phases gained to L1 increase when f2/f1 was below 1.22, and at this ratio of 1.22 DPOAE amplitudes were maximum. This result supported that DPOAE phase can be used as the indicator of the relative phase change of traveling wave of lower stimulus tone at the DPOAE generator of f2 characteristic place.