They're called the iPod Generation - all those kids wired to earbuds and MP3 players this holiday season as they hunker down to endure long road trips or relatives that visit even longer. But they're at risk of becoming the "Huh? What?" Generation.
With the increasing popularity of MP3 players - and the loud, long listening habits of today's youth - millions of children and teens are at a newfound risk of noise-induced hearing loss. Doctors around the country say they are seeing younger and younger patients with hearing loss symptoms that typically don't occur before middle age. Many of them blame constant use of iPods and other players that blare music directly into ears.
Similar concerns were raised with Sony's Walkman in the 1980s, but the difference is that the latest portable stereos hold thousands of songs and have longer-lasting batteries. Because hearing damage is directly related to the duration of exposure - not just volume - one fear is that steady, long-term exposure to even moderately loud music could result in premature hearing loss.
"Once these things became portable and full-time usable, we really started noticing more noise-induced hearing loss problems in younger children," said Dr. Robert Fifer, director of Audiology and Speech Pathology at the University of Miami's Mailman Center for Child Development.
Hearing specialists say the cases they're seeing may be only the beginning for this generation because accumulated noise damage can take years before it causes noticeable problems. The research isn't conclusive, but the warning signs are there:
The number of Americans age 3 and older with some form of auditory disorder has more than doubled since 1971, from 13.2 million to about 30 million today, according to the American Speech-Language-Hearing Association. Of those, one-third are said to have noise-induced hearing loss.
The Centers for Disease Control and Prevention reports that 13 percent of U.S. children between 6 and 19 - more than 5 million young people - have some form of noise-induced hearing loss.
More than half of U.S. high school students have at least one symptom of hearing loss, according to a 2006 poll by the association. Hispanic teens, in particular, are at risk because a greater proportion of them play their iPods at loud levels and listen longer (one hour to four hours), compared with other teens.
In October, the European Union's Scientific Committee on Emerging and Newly Identified Health Risks reported that 5 percent to 10 percent of personal music player listeners risk permanent hearing loss if they listen for more than one hour per day each week at high volume settings for at least five years.
What's too loud?
At peak volume, iPods can hit close to 120 decibels - a level between a jackhammer and a jet engine. Hearing experts say 85 decibels - the sound of city traffic - is safe. An MP3 player's range is usually 60 decibels to 110 decibels. But too many people are going beyond the recommended limits, especially when they're on the street or in crowded places and they crank the volume up.
Another alarming trend: Toy manufacturers are marketing MP3 players to children as young as 3. These devices - Bratz Liptunes, the Disney Mix Stick - produce sound well above 85 decibels, according to an analysis by the association, which says this is like "plugging virtual rock concerts" into toddlers' ears.
Hearing specialists say the cases they're seeing now may be only the start of trouble for this generation because accumulated noise damage develops slowly and insidiously. A 15-year-old who regularly cranks the volume on his player for hours at a time may not experience any noticeable problems until he or she is in their mid- to late-20s.
As part of a "Turn It to the Left" campaign, the American Academy of Audiology has produced a rap song that warns kids to turn the volume down on their MP3 players: Ahh, It ain't no funny, man, it ain't no fun, when you're 20 years old, but your ears are 81.
Fifer says he's seen early signs of noise-induced hearing loss in his patients between 8 and 16.
"The common denominator is the iPod or other similar device," he said. "They like to listen to it loud, usually so loud that Mom can hear it across the room. The general rule of thumb I give them is that they should be able to hear the conversation around them. If not, it's too loud."
A muffled world
Noise-induced hearing loss makes it difficult to understand what is being said in restaurants and other places with background noise. Conversations sound muffled, as if coming through a hotel room wall. It also becomes difficult to hear high-frequency, soft consonants, such as "s," "t," "f," "h" and the "sh" sound.
"In English, those sounds comprise more than one-third of what we speak, so you're talking about misunderstanding key words," Fifer said.
Dennis Burrows, a vice president with the American Speech-Language-Hearing Association, calls noise-induced hearing loss a "quality of life issue."
Sufferers tend to withdraw, their health often deteriorates and they can encounter problems communicating at work.
Noise-induced hearing loss happens when loud sounds stress and damage the delicate hair cells in the inner ear that convert mechanical vibrations in the air into electrical signals the brain interprets as sound. If exposed to loud noises for a long time, the hair cells can die, producing hearing loss.
Views differ slightly on what are acceptable levels and durations for listening to a player. One 2006 study by the University of Colorado at Boulder and Children's Hospital in Boston determined that a typical person can safely listen to an iPod for 4.6 hours per day at 70 percent volume. The report found no significant difference in sound levels between genres of music.
Complicating the issue is that not everyone shares the same risk of hearing loss. Some people have tougher ears, while others are more tender and prone to damage. Also, unlike speedometers on cars, most MP3 players don't warn you when danger levels are reached.
Audiologists tell listeners to subscribe to two basic rules of thumb: Keep the volume down (a good guide is to set the volume level at half) and limit listening time (to give your hearing a break).
"If you can't hear someone speaking to you and that person is just an arm's length away, then your iPod is too loud," Burrows said. "You don't have to understand every word being said, but you have to know someone is talking."