Relationship of distortion product otoacoustic emission components to psychoacoustic measures of noise induced hearing loss

Abstract

Distortion product otoacoustic emissions (DPOAEs) have promise as a tool to detect and monitor cochlear hair cell damage in noise-induced hearing loss (NIHL). However, variability in OAE amplitudes and thresholds across individuals limits their potential for detecting the early impact of NIHL. The DPOAE has two components, one generated at the point of interaction between the primaries (generator), the second reflected from the characteristic place of the DPOAE frequency (reflected). This study investigated the components of the DPOAE and how they correlate with injury. A total of 109 men, including 54 with varying degrees of occupational noise exposure, were tested. We recorded DPOAEs using logarithmically swept pure-tones and extracted the components of the DPOAE using a least-squares fit approach. Audiometry was conducted at 1.5 and 4kHz with 1dB resolution. Compressive nonlinearity was evaluated psychoacoustically with 1.5 and 4kHz pure-tones using Schroeder-phase maskers. Overall there were associations between the generator component and the psychoacoustic measures: stronger DPOAE amplitudes were associated with better thresholds and greater difference in Schroeder-phase masking threshold. Associations were stronger at 4kHz than 1.5kHz. Similar, but weaker effects were observed for the reflected component. Findings suggest that separation of DPOAE components enhances the assessment of cochlear noise-induced injury.