Effects of discotheque music on audiometric results and central acoustic evoked neuromagnetic responses

Audiograms and auditory evoked magnetic fields (AEFs) were observed in young male and female adults at different ages before and after being exposed to discotheque music for 4 hours. Sound pressure levels (SPLs) ranged from 95 dB (SPL) up to 130 dB (SPL). After exposure, subjects had temporary threshold shifts up to 20-25 dB, which almost disappeared after 2 hours. The majority of the subjects suffered from tinnitus that lasted approximately as long as the temporary threshold shift. Correspondingly, a transient delay and prolongation of the main component of the acoustically evoked magnetic field (AEF) negative wave, occurring 100 msec after stimulus (N100 m), was seen after this exposure; other components of the AEF (positive wave, occurring 50, 160, and 200 msec after stimulus [P50 m, P160 m, and P200 m, respectively]) occurred less often as compared to nonexposed controls. Because effects of vigilance on the AEF could be excluded, these changes can be related to the loud music, indicating an influence of noise on central auditory processing. The transient tinnitus could be caused by acoustic microinjuries (hidden acoustic predamage) of outer hair cells, leading to the persistent hearing threshold shifts from which many young adults aged 20-24 years are suffering. Occurrence of tinnitus closely coincides with the changes in hearing threshold and AEF, thus, a limitation of loudness in discotheques is needed to prevent this kind of hearing hazard.