Chris Clark, a Kansas University student from St. Louis, flips through his MP3 player Friday while walking through downtown Lawrence. Clark, who masters music, says he tries to keep music at a reasonable level because his hearing is key to what he does.

Hugh Murphy, of Lawrence, works on his laptop Friday while listening to jazz at Henry's, 11 E. Eighth St. Murphy said he wears headphones because he listens to music at a lower volume through them, as opposed to music through speakers.

Music can be a double-edged sword.

Some people love to listen to it with large headphones as they exercise or take a stroll down Massachusetts Street. And they like it loud.

But one of their favorite, seemingly harmless, everyday hobbies can pose a danger: it can contribute to hearing loss.

A recent study by researchers at Johns Hopkins Hospital in Baltimore found hearing loss among American adults is more common than previously thought. The study said that one-third of adults already suffer some hearing loss, even some people in their 20s or 30s.

A main cause that experts point to is repeated listening to loud music with headphones. They expect the popularity of personal listening devices to cause hearing loss to rise significantly in the future.

Medical experts say that means protecting the eardrums is as critical as ever, especially for young people because exposure to loud noises can have a cumulative and gradual effect.

“The biggest thing is just awareness because hearing loss sneaks up on you,” said Dr. Robert Dinsdale, of Lawrence Otolaryngology Associates. “It’s not typically a painful thing or something that people can see on you.”

This can be difficult, especially for younger people in Lawrence, because around here at times it can be, well, noisy. Downtown Lawrence offers several concert venues where musical groups like to rock the house.

Dinsdale says he doesn’t want to crash the party. He’s been in plenty of downtown venues for concerts, but the key usually is to wear ear plugs or to give himself a break from the loud noises.

“I look geeky, but I want to listen to music my whole life, not just early in my life,” he said.

Doctors today are also seeing plenty of risk in patients who have too much exposure to loud music while listening to iPods or other MP3 players. Give your ears a rest often, like every hour, and turn it down a notch.

If someone else can hear the music, it’s too loud, Dinsdale said.

The risks are there because when an eardrum is damaged, it’s impossible to return it to normal, Dinsdale said.

Often, exposure to a loud noise will cause a ringing in the ear for a few hours or so and then go away. But it’s a sign that repeated exposure to loud noises can cause permanent hearing damage, he said.

“Consider that a warning shot, so to speak,” Dinsdale said.