Older recordings cause most hearing damage
Beware of trains, (old) sound tracks and automobiles with the top down.
Noises from some unusual sources may be hurting our ears more than we realize.
Last summer, researchers from the University of Washington and Columbia University measured the decibel levels around all the mass-transit systems of New York City and concluded that subways were the noisiest of the lot, with about half of the readings reaching levels of 90 decibels or more, greater than those emitted by lawnmowers and power tools.
They recommend earplugs for regular riders.
"Transit-related noise levels are high enough to potentially present a risk of noise-induced hearing loss to some frequent transit riders, and this risk could increase substantially when we account for riders' other noise exposures from work and recreational activities,'' said Richard Neitzel, a noise-exposure scientist from UW.
But they caution that while earplugs and other personal protection may be useful, music headphones or earbuds generally don't help shut out other noises, and are more likely to worsen hearing loss in noisy settings as users crank up the volume to try and drown out environmental noise.
Digital-music experts note, in fact, that older recordings may be particularly harmful to the ears when listening with headphones, because the tracks may contain short sound peaks that can suddenly blast eardrums.
While some tunes have added sound-check functions or other software to smooth such peaks, the technology is still spotty.
Apple and other makers of portable music-playing devices put warnings on packaging that playing music too loudly can damage hearing - but still have volume settings that can go as high as 115 decibels. A federal appeals court recently ruled that giving listeners such an option did not constitute the sale of a defective product.
In Europe, regulators last year forced manufacturers to install volume limiters that won't allow sound levels greater than 80 decibels on players used with earphones. Apple for several years has offered a software download that limits volume for anyone concerned about potential hearing damage.
Government health and environmental agencies report that more than 138 million Americans are regularly exposed to noise levels high enough to result in hearing damage. And the National Institute on Deafness and Other Communication Disorders says that of the 28 million Americans who have some degree of hearing loss, more than a third have sustained that loss due to high noise levels.
Noise, self-inflicted or otherwise, takes a toll on the body beyond the ears. Scientists have found that noise can increase blood pressure; have negative effects on the heart, including rhythm; increase breathing rates; disturb digestion; make it difficult to sleep; and may negatively impact a developing fetus, possibly contributing to premature birth.
Still another study, reported by British scientists last year at a meeting of head and neck specialists, found that riding in a convertible with the top down at highway speeds (60 to 70 mph) consistently exposed occupants to noise levels of 88 to 90 decibels - any exposure over 85 is expected to cause permanent hearing loss.
The researchers noted that just putting the windows up cut noise levels by a few decibels, and that drivers might consider adding ear protection to their hats and sunglasses for long convertible jaunts.
Noise intrudes even in presumed quiet zones. A recent British study of hospital wards found peak decibel levels of 96 during 24 hours of measurement, noting the din was produced by everything from telephones and public-address systems to the handling of trash cans and bedpans. A stainless-steel bowl dropped to the floor rang in at 108 decibels; opening a package of surgical gloves produced 86.
The U.S. Environmental Protection Agency recommends that hospital noise levels not exceed 45 decibels during the day and 35 at night.
In the British study, an intense effort to reduce the sources of noise by nurses and other staff - from turning down phones to wearing soft-soled shoes - reduced the volume in wards by 20 percent to about 77 decibels.