The advent of the iPod has given music lovers more opportunities to immerse themselves in their favorite sounds.

But ear buds on these and other portable music players are a cause of concern for some hearing experts. Others are quick to point out that anything loud can harm hearing, and iPods shouldn't be singled out.

"We probably haven't seen the effects yet of these portable music devices," says Dr. William Avery of Sioux Valley Clinic - Ear, Nose, and Throat.

He expects to see patients in the next 10 years have some hearing loss as a result of portable music players.

The most popular version is the iPod. More than 15 million have been sold since its 2001 introduction.

The iPod's buds - which fit into the ear - increase the amount of sound pressure directed into the ear canal, says Tom Powers, chief research officer with Siemens Hearing Instruments in New Jersey. Because they seal into the ear, there is less sound escaping than in traditional headphones, he says.

Loud sounds can permanently damage irreplaceable hair cells over time. These tiny cells in the ear send information to the brain. The longer one listens to high volumes, the more likely one will develop problems.

Of the 28 million Americans who experience some degree of hearing loss, one-third can attribute it at least partly to noise, according to the National Institute on Deafness and Other Communication Disorders.

Besides hearing loss, ringing in the ears, called tinnitus, can result. Veteran rockers Pete Townshend of The Who and Ted Nugent suffer from this condition.

"We have already noticed that the baby boom generation has lost its hearing earlier than the previous generation, and we think that's because of much earlier and much more intense sound exposure," Avery said.

Young music fans should turn down the volume, experts say. But it might be difficult for them to hear an incentive to do so.

"Young people have such healthy ears that they are able to expose themselves to very loud sound, and they don't have the pain or discomfort that goes with it," Avery says. Only as they grow older will the negative effects of loud music likely become noticeable.

Krolikowski says she never listens to music at full volume on her iPod because the sound gets distorted. But when it comes to long-term prevention of hearing loss, "I don't really think about it," she says.

Dr. Colin Driscoll at Mayo Clinic in Rochester, Minn., advises music fans to turn up only the good songs and turn down the others. That gives ears a break.

Experts say if headphones can be heard by people other than the wearer, the music is probably too loud. It shouldn't be much louder than conversational speech, Avery says.

Loud music, of course, isn't the only sound to be wary of. Lawn mowers, subway stations and car horns also tend to have high decibel levels of 70 decibels or more. In comparison, a busy, noisy office is about 60 decibels.

"I guarantee you, people aren't going to lose their hearing so much from the iPod," Driscoll says. "It's because they shoot or hunt or work with power tools or heavy equipment and didn't wear ear protection."

By Monica Labelle, Argus Leader