Evaluation of supra-threshold hearing following an event of recreational acoustic exposure

Studies with small rodents have exhibited physiological evidence of noise-induced cochlear synaptopathy prior to outer-hair-cell loss following noise-induced large temporary threshold shifts (TTS). The auditory system may thus not fully recover after a TTS. If this noise-induced damage also occurs in humans, this may have consequences for sound processing at supra-threshold levels, especially speech in background noise, and may also challenge current noise regulations.

The aim of this study was to investigate if human listeners with normal hearing sensitivity show signs of cochlear synaptopathy after participating in a concert. Young adult listeners with hearing thresholds ≤ 20 dB HL between 0.25-8 kHz were recruited and divided into two groups: listeners voluntarily participating in concerts and control listeners with no concert participation during the study.

Exposure was assessed with dosimeters in both groups for one event duration. Concert participants were advised to use hearing protectors and exposure levels were determined from actual use. Listeners performed three sessions of audiometry, auditory brainstem response (ABR), and speech in noise measurements.

Session 1 was performed within a week up to the concert, session 2 within 24 hours after the concert, and session 3 approximately 4 weeks after the concert. We hypothesized that concert participants would show reduced level-growth of ABR wave I and that wave-I level-growth would be a predictor of speech discrimination score.

The data indicate that postexposure wave-I level-growth was not reduced compared to pre-exposure values, and that neither were speech scores. Therefore, the results might suggest that: a) concert goers do not develop cochlear synaptopathy in response to typical exposure from one event, or b) synaptopathy occurs only for more severe exposure in humans, or c) the utilized measures are not sensitive enough to detect the damage.