Sensitivity of distortion product otoacoustic emissions in noise-exposed chinchillas.

The present study investigates the effect of small amounts of outer hair cell (OHC) loss on distortion product otoacoustic emission (DPOAE) levels and evoked potential permanent threshold shifts (PTS) in a population of 12 noise-exposed chinchillas. The group mean DPOAE level, which decreased by up to approximately 15 dB in the presence of less than 8 dB PTS and 15% OHC loss, indicates that DPOAEs can detect an underlying cochlear pathology (i,e., OHC damage/loss) despite the presence of normal to near normal thresholds. The sensitivity of DPOAEs in detecting OHC loss makes this test measure suited for diagnosing sensorineural hearing impairment, particularly when abnormal auditory symptoms (i.e., speech discrimination problems) are associated with a normal audiogram in the clinical setting and as part of a hearing conservation program.