The effect of impulse noise exposure on distortion product otoacoustic emissions in the awake guinea pig.

Distortion product otoacoustic emissions (DPOAE) are a sensitive detector of outer hair cell (OHC) function and were monitored in awake guinea pigs before and after impulse noise damaging the cochlea (peak intensity 153 dB SPL, rise time < 0.1 ms). Animals had stable DPOAE levels before noise exposure. In the first hours after noise exposure DPOAE levels were reduced significantly. Three different patterns of recovery of DPOAE were seen in the post-exposure period:restitution exceeding controls, partial recovery and no recovery. In general, DPOAE levels declined and types of recovery closely corresponded to changes in amplitudes of cochlear microphonics after noise exposure. These data suggest that the monitoring of DPOAE is a suitable method for diagnosing impaired OHC function.