Evaluation of Transient and Distortion Product Otoacoustic Emissions before and after shooting practice

Firearms are a common source of impulse noise that may potentially damage a hearing organ. It is not easy to predict soldiers' personal susceptibility to noise exposure. The purpose of this study was to evaluate of the transient evoked otoacoustic emission (TEOAE) and distortion-product otoacoustic emission (DPOAE) before and after shooting and compare it with conventional pure tone audiometry. Standard pure tone audiometry, tympanometry, TEOAE and DPOAE measurements were recorded before and 10-15 minutes after shooting. Ten male soldiers (20 ears) were exposed to impulse noise from automatic gunfire (15 single rounds of live ammunition). They did not use any earplugs. The reduction in amplitude of the TEOAE after shooting was 3.1 and 5.1 as SPL for 3 and 4 kHz respectively for the right ear and 4.3 dB SPL for 1 kHz and 0.6 dB SPL at 2 kHz for the left ear. The greatest reduction in DPOAE occurred at frequencies of 1.0 kHz (3.8dB SPL) and 3.0 kHz (2.9 dB SPL) for the left ear. There were no differences in the audiometric thresholds before and after shooting. Emissions appear to be more sensitive for monitoring early cochlear changes after shooting, than pure tone audiometry.