Parents, if your teenager is listening to her iPod nearby and she's not the only one who can hear all the lyrics to the latest Katy Perry song, chances are that the volume is turned up too high.

A recent study published in the Journal of the American Medical Association revealed that, according to a 2005-06 survey of 1,771 people ages 12 to 19, one in five teens suffer from at least a slight level of hearing loss. A similar national survey taken in 1988-94 indicated that one in seven teens suffered mild hearing loss, which could make it difficult to hear someone whispering into an ear. Since the first sampling, the percentage of teens affected has risen from 14.9 percent to 19.5 percent.

Dr. Blake Strand, head of audiology at Midwest Hearing Aid Systems in Woodbury, a division of Midwest Ear Nose and Throat Specialists, said he's not surprised that parents might be quick to blame iPods or other MP3 players for the study results, given the fact that today's teens seem to spend a lot of time plugged in.

"Twenty years ago, parents thought that Walkmans would ruin their kids' hearing. The difference with the current music technology is that kids can listen for longer periods -- sometimes for up to eight hours at a time -- without having to take a break or recharge the device," said Strand. "Today's headphones also produce higher sound levels directly into the ear canal."

A very loud noise

An iPod cranked to its highest volume -- 105 to 110 decibels -- would exceed Occupational Safety and Health Administration limits for hearing damage if that level was maintained for more than an hour. Strand suggests setting the volume limit on an iPod to no more than 70 percent, especially for younger children.

"The brain adapts to a higher volume level, so by setting limits when kids are younger, it will help them not to habituate to those louder levels," he said.

Teens tend to crank up the volume if they are listening to their iPods in places with ambient noise, such as school hallways, coffee shops or gymnasiums. Consider purchasing a pair of noise-canceling headphones, which can help reduce the ambient noise, so the volume can then be kept at a lower level.

More to it than iPods

Strand called the results of the recent hearing study "fairly alarming but not unexpected." He maintains, however, there may be additional causes for teen hearing loss besides frequent use of iPods and MP3 players. Environmental factors such as excessive traffic noise or loud sports/concert stadiums can affect hearing. "Our world has certainly gotten noisier," he said.

Because young people frequently believe they are invincible, teens might not fully appreciate the fact that once any hearing is gone, it's gone. Hearing loss adds up over time; excessive noise exposure can eventually limit one's ability to hear higher frequencies and make it harder to distinguish "f, s and th" sounds.

"You might not notice it at first, but eventually, it can become more difficult to hear in situations where there is background noise, like a classroom," said Strand. "It can have an impact on young people both educationally and socially."

While Strand said he hasn't experienced an increase in teen patients coming in and complaining of hearing loss, he expects that may change over the next few years.

Despite the advancements in hearing aid technology, as many devices are now equipped with wireless networking or Bluetooth capabilities, Strand isn't exactly hopeful that the "cool factor" of today's hearing aids will appeal to young people.

"We don't want to see them having to get hearing aids when they are in their 40s and 50s instead of in their 60s and 70s," he said.

Julie Pfitzinger is a West St. Paul freelance writer. Have an idea for the Your Family page? E-mail us at tellus@startribune.com with "Your Family" in the subject line.