Studies, for instance, have detailed exposures at events such as rock concerts and nightclub shows, including one meta-analysis that measured an average of 103 decibels and frequent higher peaks. At levels experienced by rock concert-goers and football fans alike, the effects are not necessarily obvious right away. Hearing loss develops slowly over years, but is no less serious for it. At 100 decibels, the safety zone ends within two hours. At such levels and durations, researchers say cells in the inner ear are killed, never to be replaced.
Scar tissue takes over.
But because low-level damage is subtle, hearing loss may not be detected for weeks or years. If in doubt, have your hearing tested by an audiologist. While there is little public awareness of the risk from non-occupational noise, as a National Institutes of Health consensus panel concluded in 1990, the government has largely sidestepped the issue. Perhaps, he says, there shouldn't be. They're probably doing a good job at keeping the music down to an okay level.