Call it acoustic trauma or noise-induced hearing loss. By any name, it's the most important preventable cause of permanent hearing loss. Up to 28 million Americans have impaired hearing; for as many as a third, acoustic trauma is a significant contributor, reports the December 2007 issue of Harvard Men's Health Watch.
Acoustic trauma is a product of modern life. On-the-job noise exposure is the most common cause, but recreational noise — such as loud music — is catching up. If present trends continue, the condition may someday be known as "iPod ear."
A sound's potential to damage the ear depends on the duration as well as the intensity of the sound. How much sound is dangerous? The Occupational Safety and Health Administration offers guidelines: Sounds below 75 decibels (dB) are safe, but eight hours at 85 dB can be harmful. (The sound of a lawnmower or heavy traffic is approximately 90 dB.)
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