Between iPods, Concerts and Sirens, the volume is turned way up for kids today, but they're hearing less, reports CBS News chief medical correspondent, Dr. Jon LaPook
"There's been a pretty significant increase in hearing loss over this time period in American adolescents," said Dr. Josef Shargorodsky, an otolaryngologist at the Harvard-affiliated Massachusetts Eye and Ear Infirmary, who discovered the findings and co-authored the report in the Journal of the American Medical Association.
The study of almost 5,000 adolescents found one in five suffers some hearing loss, mostly slight and more common in boys.
While the study did not conclude what's behind the increase, here's how loud noise can cause harm:
Sound waves travel through the ear canal to the inner ear. There, tiny hair cells convert the sound into nerve impulses that travel to hearing centers in the brain. Excessive noise can damage those cells and cause permanent hearing loss.
So how loud is too loud? Prolonged exposure to 85 and above can cause gradual hearing loss. A few miles north of Times Square is 80. With sirens, it's 88. Music players like iPods can top 100 decibels when turned all the way up.
Audiologist Brian Fligore used a mannequin equipped with sensors to measure just how loud kids are playing their music. Most (58.2 percent) were listening at unsafe levels.
"If you were to listen all the way up, maximum, you can really only listen for about five minutes a day before you're starting to increase your risk for hearing loss," said Fligore.
16-year-old Lindsey Claus was diagnosed with hearing loss from playing the French horn in an orchestra.
"My hearing sounded strange," said Claus. "It sounded muffled, it didn't sound like what I would normally hear."
"It is possible that teenagers' ears are a little more susceptible and if nothing else, they're certainly going to have a longer life in order to deal with hearing loss if it sets in early," said Fligore.
Parents should consider the possibility their teen has hearing loss if he or she is doing poorly in school or constantly asking "what??" -- even more than the average teenager.