Researchers fear that the growing popularity of portable music players and other items that attach directly to the ears will continue to increase hearing loss.

"It's a different level of use than we've seen in the past," says Robert Novak, director of clinical education in audiology at Purdue University in Indiana. "It's becoming more of a full-day listening experience, as opposed to just when you're jogging."

Novak says he's seeing too many young people with "older ears on younger bodies."

Novak is not the only physician reporting an increase in this trend.

"It may be that we're seeing the tip of the iceberg now," says Dr. John Oghalai, director of The Hearing Center at Texas Children's Hospital in Houston, who's treating more of this age group. "I would not be surprised if we start to see even more of this."

A survey published this summer by Australia's National Acoustic Laboratories found, for instance, that about 25 percent of people using portable stereos had daily noise exposures high enough to cause hearing damage.