A Longitudinal Study of Changes in Evoked Otoacoustic Emissions and Pure-tone Thresholds As Measured in a Hearing Conservation Program

Non-linear transient-evoked otoacoustic emissions (TEOAEs) at 74dB pSPL, distortion-product otoacoustic emissions (DPOAEs) at 65/45dB SPL and pure-tone audiometry were used to detect noise-induced, inner car changes in a longitudinal study. Repeated-measures ANOVAs were made on the Noise (n=69) and Quiet (n=42) groups. The Noise group's hearing thresholds increased by 1.2 dB and DPOAE amplitude decreased by -0.9 dB. For both groups, TEOAE amplitude decreased by approximately -0.6 dB. Eight of 12 ears with permanent threshold shift (PTS) and 10 of 13 ears with temporary threshold shift (TTS) showed TEOAE decrements or low baseline TEOAE amplitudes. Fewer TTS and PTS ears also showed DPOAE decrements, and there was never a DPOAE decrement without a corresponding TEOAE decrement or low TEOAE baseline. Some TTS ears showed permanent emission decrements. Although otoacoustic emissions show promise in detecting noise-induced inner ear changes, it is premature to use them in hearing conservation programs.