IPods and Hearing Loss

WSJ.com - Behind the Music: IPods and Hearing Loss :: Some Doctors Raise Concerns
That MP3 Players May Cause Damage With Heavy Use By JANE SPENCER : "Similar concerns were raised when the first generation of portable music players, including Sony Corp.'s Walkman, hit the market in the 1980s. But the latest portable stereos -- including Apple Computer Inc.'s iPod, and other players by iRiver, Sony and SanDisk -- can hold thousands of songs and have longer-lasting batteries than older players. As a result, people are listening to the devices for much longer periods of time. Because hearing damage is directly related to the duration of exposure -- not just the volume -- one concern is that the steady, long-term exposure to even moderately loud music could contribute to premature hearing loss.

Hearing specialists at centers such as the House Ear Institute in Los Angeles, Children's Hospital Boston and the American Academy of Audiology say the effect they are seeing now may be only the beginning, because accumulated noise damage can take years before it causes noticeable problems. "We're only seeing a few teenagers with hearing loss at this point," says Brian Fligor, director of diagnostic audiology at Children's Hospital Boston. But, he adds that many others may have subtle hearing loss that they have yet to recognize, "and by the time they do, they'll have done substantial damage."

The concerns are emerging as sales of MP3 players explode. Roughly 38 million MP3 players were shipped to U.S. retailers in 2005, according to forecasts by the research firm IDC, and an estimated 28% of the U.S. population owns a player. Apple controls about 70% of the MP3 player market, according to the research firm NPD Group. At peak levels iPods can hit volumes close to 115 decibels, research has found -- a level that falls somewhere between a chainsaw and jackhammer -- but all MP3 players pose an equal theoretical risk.

There are two ways that noise exposure leads to hearing damage. Brief exposures to extremely loud sounds, like gunfire, can cause permanent damage. But consistent exposure to even moderate-level loud sounds wears out the hair cells in the inner ear, which are responsible for acute hearing abilities. When these cells are damaged by noise exposure -- like a loud concert -- they typically recover after two days of rest. With repeated exposure to loud sounds, however, the hair cells' ability to recover weakens. Eventually the hair cells die, leading to permanent hearing loss."