domingo, 13 de diciembre de 2009
All That Noise Is Damaging Children’s Hearing
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By JANE E. BRODY
Published: December 8, 2008
Michael became hooked on headphones in his early teens. He walked the streets of Brooklyn day after day with his favorite music blasting directly into his ears. By his early 20s, the sensory hair cells in his inner ears had been permanently damaged and Michael had lost much of his upper-range hearing.
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The Children’s Hearing Institute reports that hearing loss among children and young adults is rising in the United States, and that one-third of the damage is caused by noise.
According to the American Academy of Audiology, about one child in eight has noise-induced hearing loss. That means some five million children have an entirely preventable disability that will stay with them for life.
The academy has begun a “turn it to the left” (the volume dial, that is) awareness campaign in hopes of protecting current and future generations of youngsters from unwittingly damaging their hearing. Often, the problem is not detected until children develop persistent ringing in the ears or begin to have learning or behavior problems in school because of trouble understanding speech.
Although newborns are now routinely screened for hearing loss, there is no federal mandate for screening the hearing of school-age children. What testing is done often fails to check hearing at high enough pitches, a federal research team pointed out in the journal Pediatrics.
Surrounded by Noise
We live in a noisy world. Young and old alike are beset by sounds over which we may have little or no control: power mowers, leaf blowers, snow blowers, car and house alarms, sirens, motorcycles, Jet Skis, loudspeakers, even movie previews.
We attend rock concerts, weddings, parties and sports events at which the music is so loud you can hardly hear the person sitting next to you. At home, televisions, stereos and computer games are often turned up so loud that listeners cannot hear a doorbell or a telephone.
Many “modern” restaurants have opted for noise enhancement instead of abatement. And try having a conversation in a school cafeteria at lunchtime.
Any time you need to shout to be heard by someone near you, your hearing is most likely to be in a decibel danger zone.
As if environmental noise were not enough, now we besiege children with noisy toys and personal listening devices that can permanently damage their hearing. Toys that meet the safety standards of the American Society for Testing and Materials can produce sound up to 138 decibels, as loud as a jet taking off. Yet workplace rules require hearing protection for those exposed to noise above 85 decibels.
A series of studies conducted in 2002 among 116 infants by researchers at Johns Hopkins indicated that even moderate background noise can interfere with how they learn language. The effect on babies’ hearing in a noisy house is similar to what an older person with age-related hearing loss may encounter at a crowded cocktail party.
A landmark study in 1975 found that children in classrooms on the noisy side of a school had lower reading scores than those whose classes were on the quiet side.
Noise-induced hearing loss can come about in two ways: from a brief exposure to a very loud noise or from consistent exposure to moderate-level noise. Thus, there is much concern about the lasting effects of MP3 players that are turned up loud enough to block out surrounding sound, like street noise. An MP3 player at maximum volume produces about 105 decibels — 100 times as intense as 85 decibels, where hearing damage begins. (For every 10 decibels, sound intensity increases tenfold.)
The National Institute for Occupational Safety and Health says 110 decibels can produce hearing damage after just 1 minute, 29 seconds of exposure. The League for the Hard of Hearing cautions that “noise levels above 85 decibels will harm hearing over time” and that levels above 140 decibels — the pain threshold — can damage hearing after just one exposure.
New bone-conduction headphones that hook over the ears and pass sound through the skull to the inner ear may not solve the problem. While they allow listeners to hear an oncoming car or a person speaking, users may turn up the volume to overcome ambient noise, damaging the 15,000 tiny hair cells in the inner ear that transfer sound energy to the brain.
Once damaged, hair cells can neither be repaired nor replaced. The damage makes it difficult to hear high-pitched sounds, including certain speech sounds and the voices of women and children. Tinnitus, a continuous ringing, roaring or clicking in the ears, can also result.
Protecting Young Ears
Before buying noisemaking toys, parents would do well to listen to how loud they are. If the item comes with a volume control, monitor its use to make sure it is kept near the lowest level. Consider returning gifts that make loud noises, or disable the noise-making function. Or restrict the use of noisy toys to outside play areas.
Children who play computer games and stereo equipment should be warned to keep the volume down. Time spent in video arcades, where the noise level can exceed 110 decibels, should be strictly limited. Most iPods have a control that allows parents to set a maximum volume.
Avoid taking children to loud action movies. If you do go and the sound seems deafening, ask the management to turn down the volume or insist on your money back. Children who play in bands and teenagers who use power tools, gardening equipment or guns should be made to wear hearing protection, available at pharmacies and hardware and sporting goods stores.
The League for the Hard of Hearing urges parents to encourage participation in quiet activities, like reading, watching family-oriented films, doing puzzles, making things with construction toys, playing educational computer games, drawing and painting, and visiting libraries and museums.
A version of this article appeared in print on December 9, 2008, on page D7 of the New York edition.
Fuente: The New York Times, HEALTH,