Parents: You can breathe a small sigh of relief — and probably give your children back their iPods.
Last month’s headline-grabbing study that estimated that as many as 19.5 percent of children have a noise-induced hearing loss (a jump from the 14.9 percent of a decade earlier) may have exaggerated the problem — by as much as two-thirds, according to University of Minnesota researchers.
That means it’s likely that fewer than 7 percent of children and teenagers have a hearing loss caused by exposure to loud sounds. That’s still a number that should concern us, for hearing difficulties are associated with learning problems, poorer performance in school and lower self-esteem. But it’s not a number that should make us overly fret about our kids’ iPods and other portable listening devices.
Why do the U of M researchers think estimates of noise-induced hearing loss are off by so much?
“It’s just some complications in the measurements,” said Bert Schlauch, a professor in the Department of Speech-Language-Hearing Sciences, in a phone interview Monday. Schlauch and his study co-author, Edward Carney, used computer simulation modeling to determine the statistical properties of hearing tests. They found that measurement errors in the tests likely produced false-positive results in up to 10 percent of all children tested.
The findings were published online last week in the Journal of Speech, Language, and Hearing Research.
Measurement errors are common in hearing tests, Schlauch said, and can be caused by something as simple as the way the headphones are put on.
“The earphone goes over the ear, and if it doesn’t line up with the ear canal, those higher frequencies show a loss,” he said. (An inability to hear high-frequency, or high-pitch, sounds is the tell-tale sign of a noise-induced hearing loss.)
Sometimes, the hearing test equipment can partially collapse the ear canal, causing temporary hearing difficulties — a situation that occurs frequently when testing children, Schlauch added.
The inconsistency of hearing test results have been a major finding in other ongoing research by Schlauch and Carney involving students in the U of M’s marching band. Using standard methods of measuring hearing, the researchers found that about 15 percent of the band students demonstrated a noise-induced hearing loss. But the results for individual students changed as they as were re-tested over a period of a year. When all the results were averaged for each student, more than half of the observed noise-induced hearing loss disappeared — strongly suggesting measurement error.
Schlauch says we should still be concerned about exposing our children (and ourselves) to unnecessary and potentially damaging noise — including that produced by revved-up iPods and other portable listening devices.
“What we don’t know is who is really more susceptible to these intense sounds,” he said. “Some people’s hearing is damaged much easier than others, and we currently don’t have a way of predicting that.”
Parents need to educate their kids about the danger of turning up the volume too loud. “If someone is listening [to music through a portable device], and it’s at a comfortable level, it won’t cause a hearing loss,” he said. “But some people like their music really loud, and for those people, they may be placing their hearing at risk.”
“If you hear sound coming out of the earphone when you’re on the other side of the room, that’s too loud,” he added.
Parents, take note.