ELECTROPHYSIOLOGICAL MEASURES OF AUDITORY IMPAIRMENT IN NOISE-EXPOSED, NORMAL-HEARING SOLDIERS

Abstract

IntroductionSome electrophysiological changes can occur in the auditory system in response to noise exposure with or without any permanent auditory threshold shift. The purpose of this study was to identify and measure cochlear function after noise exposure in individuals with normal hearing according to standard audiometric thresholds.Material and methodsPure tone audiometry (PTA) over the standard 0.250–8 kHz range and at 12 kHz, as well as distortion product otoacoustic emission (DPOAE) and auditory brainstem response (ABR) testing, were performed on 42 soldiers who had participated in combat. A control group of 40 participants underwent the same tests.ResultsIn the noise-exposed group, significantly poorer PTA thresholds were recorded at 12 kHz. DPOAE levels were significantly low only at 4 kHz. On ABR testing, both wave I and wave V demonstrated a significant decrease in amplitude and a significant increase in latency for the noise-exposed group.ConclusionsOur findings reveal that high levels of noise can not only damage outer hair cells but also cause changes at the level of the synapses (synaptopathy) which are not evident using standard PTA tests. However, electrophysiological methods can detect some changes in cochlear function.