If a sound level of 85 decibels is endured for eight hours, permanent damage can result. At 100 decibels, permanent damage can result after as little as 15 minutes. Above 120 decibels, the damage can be both permanent and immediate.
Noise-induced hearing loss afflicts roughly 10 million Americans. Hearing loss occurs when the microscopic hair cells found in the cochlea are broken or damaged. The loss may be sudden or cumulative. An idling bulldozer can generate 85 decibels, and a personal music system using headphones can generate more than 100 decibels when played at full volume. Depending on the proximity to the stage, a listener at a very loud rock concert can be exposed to levels exceeding 115 decibels.