Distortion product otoacoustic emission fine structure as an early hearing loss predictor

Otoacoustic emissions (OAEs) are a promising method to monitor early noise-induced hearing losses. When distortion product otoacoustic emissions (DPOAEs) are obtained with a high-frequency resolution, a ripple structure across frequency can be seen, called DPOAE fine structure. In this study DPOAE fine structures are obtained from 74 normal-hearing humans using primary levels of L1/L2=65/45 dB. The subjects belong to groups with different ages and exposure histories. A classification algorithm is developed, which quantifies the fine structure by the parameter's ripple place, ripple width, ripple height, and ripple prevalence. Temporary changes of the DPOAE fine structure are analyzed by measuring DPOAE both before and after exposing some of the subjects to an intense sound. The characteristic patterns of fine structure can be found in the DPOAE of all subjects, though they are individual and vary from subject to subject within groups. The results do not indicate that the DPOAE fine structure alters with the state of hearing, as it is suggested in the literature. The data analysis is still in process at this stage.