GAINESVILLE---For the typical teen-ager, graced by the taken-for-granted health of youth, hearing loss might seem as remote as Alzheimer's disease--a problem to be faced decades from now, if ever.
But University of Florida research shows that 17 percent of middle- and high-school students already have lost some ability to hear. And the problem will keep getting worse if they don't protect themselves from the piercing decibels of loud music, motorcycles, target-shooting and other assaults on their ears.
"They probably haven't noticed that they have lost the ability to hear very high pitches, such as that of a dog whistle," said Alice Holmes, associate professor of communicative disorders in UF's College of Health Professions. "It isn't affecting their day-to-day life yet. But the more they are exposed to loud noises, the more damage will be done. As time goes by, they will have increasing difficulty understanding conversation. They may wind up being candidates for hearing aids."
Can't trust such dire talk from an ivory tower researcher--or a parent with a headache? Plenty of rockers, including The Who's Peter Townshend and most of the heavy metal group Metallica, will testify that they don't hear so well anymore. Excessive noise has permanently damaged the cochlea, tiny hair-like receptors in the inner ear that are instrumental in transmitting sounds to the brain.
Holmes' team screened 342 middle and high school students in Gainesville. Schools typically test younger children to check for hearing problems that escaped attention during toddler years. But it's long been assumed that there were no worries for middle- and high-schoolers. "There has been very little research on this age group," Holmes said.
The students, ages 10 to 20, underwent pure-tone screening in both ears. Test administrators asked them to indicate when they heard a beep. The beeps were 20 decibels loud at pitches ranging from 1,000 to 6,000 hertz (cycles per second). "One thousand hertz is equivalent to about a middle C on the piano, and the tests went up in pitch from there," Holmes said.
Seventeen percent of the students did not hear one or more of the sounds in at least one ear. They were most likely to fail at the highest pitch tested. Two students did not hear any of the tones in either ear, and five students failed all frequencies in one ear but passed in the opposite ear.
"These results should serve as a warning that today's young people, who often have their headphones or car stereos cranked up high, are at great risk for losing some of their hearing in the coming years," said Holmes, who published her research earlier this year in Language, Speech, and Hearing Services in Schools, a journal of the American Speech-Language-Hearing Association.
"But the good news is that noise-induced hearing loss is preventable. We can educate children about how to protect their ears. And if we screen more people, we can detect problems when they are mild, and urge stronger precautions for those who appear particularly susceptible to losing their hearing."
Without screening, most people suffering early hearing loss do not realize it. "It's very common for someone who has a high-frequency hearing loss to comment that 'I hear fine, people are just mumbling,'" Holmes said.
Susceptibility to noise-induced damage varies considerably. "You can go into a factory and find two people who have worked side by side with the same noise exposure and one of them will develop a severe hearing loss and the other one won't," Holmes said. "It might be genetics, but we don't really know. This area is wide open for more research."
Holmes recommends wearing earplugs or other sound protection when mowing the lawn, working with noisy equipment, riding a motorcycle or attending a rock concert. "Today there are earplugs available that are like comfortable little sponges," Holmes said. "You won't even know they're there."
People who like to hunt or shoot target practice also need to take precautions. Holmes' research showed that students who use firearms were more likely than others to have lost some hearing ability.
"A good rule of thumb is, if you're in a noisy environment and you have to significantly raise the level of your voice to be heard, that noise is loud enough that it risks hurting your ability to hear," Holmes said.