The Psychophysics Psyber Lab

 

 

 

Changes in evoked otoacoustic emissions and hearing thresholds after a six-month deployment on an aircraft carrier.

Lynne Marshall, Judi Lapsley Miller, Laurie Heller, Linda Hughes, & Linda Westhusin

January 2002
Poster presentation at the 2002 ARO conference
Assoc. Res. Otolaryngol Abs. 25.

Abstract

Evoked otoacoustic emissions and hearing thresholds were measured in 339 sailors from the USS Dwight D. Eisenhower aircraft carrier before and after a six-month deployment to the Mediterranean. Sailors from the Air, Reactor, and Engineering departments were targeted because they were considered most at risk for noise-induced hearing loss. At pre-deployment and post-deployment testing, hearing thresholds (0.5 to 6 kHz) were measured using a modified Hughson-Westlake procedure and normal middle-ear pressure was established. Transient-evoked otoacoustic emissions (non-linear click stimulus at 74 dB pSPL) and distortion-product otoacoustic emissions (f2/f1=1.22, at four stimulus levels) were then measured using the Otodynamics ILO292 Echoport. There was no consistent change in average hearing thresholds for the group; however, some individuals showed significant threshold shifts. Temporary threshold shifts were confirmed for two sailors (two ears) and permanent threshold shifts were confirmed for fifteen sailors (eighteen ears), based on their noise history and a confirmatory audiogram. Some additional significant threshold shifts were unable to be confirmed. Preliminary group results indicated that after deployment there was a decrease in average distortion-product and transient-evoked otoacoustic-emission amplitudes. Changes in otoacoustic-emission amplitudes might be a more sensitive indicator of noise-induced damage to the inner ear than changes in hearing thresholds.

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