iPods can be a hazard to your hearing, but noise canceling headphones may help

If you or a family member get an iPod this holiday season, make sure you and your loved ones know how to enjoy MP3 players and other personal music devices without permanently damaging hearing.

A new study on hearing loss from personal music players comes from the European Union, which found that 5 to 10 percent of EU's MP3 listeners—as many as 10 million people—are at high risk of developing noise-induced hearing loss after 5 years of exposure. Previous studies have found risks for U.S. listeners as well.

Noise-induced hearing loss is caused by a combination of the loudness and duration of your exposure to loud noise, primarily through damaging the hair cells inside the ear that convey sound into the nervous system. The louder the noise, and longer the exposure, the greater the risk to those hair cells, and the faster hearing loss can occur.

Furthermore, you become desensitized to noise the longer you listen to loud sounds.  So unless the noise is so loud that you immediately notice discomfort, pain, or ringing your ears, you might not even notice damaging noise until long after it stops and your ears readjust to normal.

So how loud is too loud? Experts don't agree. For example, the National Institute for Occupational Safety and Health says employers should provide hearing protection when the volume reaches 85. Authors of the EU report conclude that exposure of more than five hours a week at levels exceeding 89 decibels over five years could put you at risk of permanent hearing loss. The U.S. Environmental Protection Agency recommends no more than 70 decibels over 24 hours of exposure for the general population.

Anyone can suffer from the effects of even slight hearing loss, but young people and children may be at a special risk for added complications. Hearing loss is cumulative, so early damage may increase the ultimate severity of hearing loss later in life. If you or anyone in your family logs a lot of iPod hours a day, make sure to understand the risks, and follow these steps to help reduce them.

Be wary of noise-on-noise. Some environments, such as the subway, a gym, or even a busy street, may approach or exceed risky noise levels, so turning up your music player to drown out ambient noise may put your hearing at further risk. Try to avoid listening to your player in these conditions regularly or for long periods.

Eliminate surrounding noise. Noise canceling headphones use electronic circuitry to eliminate or reduce unwanted noise. By blocking out the surrounding noise, you may be able to keep your music below risky levels, even in noisy surroundings. In our tests, we found that other headphones that fit snugly around the ear or inside the ear canal were also able to block out some outside noise, which may be helpful.

Be particularly cautious if you use ear bud-type headphones, such as those that come with the iPod, or loosely fitting on-ear models. One study found that 80 percent of listeners using headphones with virtually no sound isolation exceeded 85 decibels in a lab that simulated airplane cabin noise. And the EU report found that in the worst-case scenario, an ear bud-type headphone hooked up to an MP3 player could deliver up to 120 decibels, the equivalent of an ambulance siren at close range.

Limit maximum volume. You may also be able to set a maximum volume level for your or your child's MP3 player. Recent iPod models allow you to set and lock the volume control, as do many other brands. Some university researchers have recommended limiting the iPod with ear bud earphones to 70 percent of maximum volume for use up to 6 hours a day, or 80 percent for up to one-and-a-half hours. The manufacturer of the Zen MP3 player provides recommended maximum levels. See our Ratings (available to subscribers) to find out which MP3 players have volume limiters, or check the instruction manual or the manufacturer's Web site.

Consider your overall exposure to noise. Noise-induced hearing loss is cumulative. Loud concerts, dance clubs, sporting events, and loud yard equipment, such as power blowers or lawn mowers, are just few exposures to watch out for. Protect your hearing in these environments, and you may be able to enjoy more listening time from your MP3 player now and reduce the need for a hearing aid later on.

—Kevin McCarthy, associate editor

If you or a loved one has a pacemaker or implantable cardioverter defibrillators (ICD), you'll want to take a look at our note on headphone safety.