Listening to your iPod at full blast before an 8 a.m. class may wake you up, but new studies show long-term problems can arise from overuse of MP3 players.

A recent study of 100 doctoral students concluded that people who listen to music at about 80 percent of volume capacity should not exceed 90 minutes per day. Permanent hearing loss may be sustained if this guideline is not followed, according to the study.

Loud noises can permanently damage hair cells that sit in the cochlea, which is the snail-shaped part of the ear, said Elise Uhring, Penn State audiologist and instructor.

"If the noises are loud enough for a long enough period of time, the hair cells can be damaged permanently," Uhring said. "It really only takes one time."

But how loud is too loud? Any noise above 85 decibels can potentially cause hearing loss, said Tom Frank, professor of communication sciences and disorders. Eighty-five decibels is equal to 60 to 80 percent of an MP3 player's maximum level.

To put that in perspective, normal conversation falls between 50 and 60 decibels. Many older iPods can reach 120 decibels -- far beyond what is considered safe.

Most students did not seem concerned about potentially damaging their hearing. Emily Winchatz (freshman-division of undergraduate studies) said she listens to her iPod at about 75 percent of the maximum level at the gym or walking to class.

"I never really thought about it [the potential for hearing loss] before," she said. "I think my hearing's pretty good."

Likewise, Brendan Duffy (junior-crime, law and justice) said he listens to his iPod every day for about three hours.

"It never really crossed my mind," he said.

This attitude may perpetuate the problem, Uhring said.

"Just because you're not noticing [hearing loss] now, doesn't mean it's not happening," Uhring said. "If you have your iPod on, it should be turned to a volume that no one else can hear and quiet enough that you can still hear others conversing."

MP3 players are not the only source of potential hearing loss. Frank cautions that any noise above 85 decibels, if sustained for a sufficient period of time, can cause permanent hearing loss. A loud rock concert can reach 115 decibels, and many bars and nightclubs are just as noisy. Even football cheers at Beaver Stadium can climb to more than 105 decibels.

Ironically, many gyms and aerobics studies play music between 100 and 110 decibels.

"You go to the gym to get healthier, but at the same time you're damaging your hearing," Frank said.

To prevent hearing loss, students should wear earplugs or other forms of ear protection when exposed to noises greater than 85 decibels and listen to iPods and other MP3 players at low volumes, Uhring said.

"Remember, you only have two ears. You'll never get another pair," Uhring said.