If you’ve ever ridden a subway, particularly New York’s aged system, you’ve probably experienced the ear-splitting shrieks as the train takes a fast turn or screeches to a halt. Those sounds are more than just annoying; they can actually contribute to hearing loss, according to a new study published in the August edition of the American Journal of Public Health.
Researchers took sound level readings while waiting for and riding buses, trains, subways and ferries in the New York metro area, and found that subways were the loudest. But they also found that all commuter systems were loud enough to cause noise-induced hearing loss in some riders, given sufficient length of exposure.
How long? The actual risk varies from person to person. But according to the researchers the highest maximum sound level of 102 decibels, recorded at a subway platform, could cause hearing loss over time for some people within just two minutes a day—based on guidelines from the Environmental Protection Agency. The average sound level for the entire New York subway system of 80.4 decibels could cause hearing loss if regular exposure exceeds about an hour and 40 minutes a day, or just 18 minutes per day on some of the noisiest platforms averaging 90.2 decibels.
And with iPods and cell phones now ubiquitous, subways themselves may not be the only in-transit exposure. "Imagine someone on a subway who is getting 80 decibels of exposure in the car," explains Rick Neitzel, a research scientist at the University of Washington in Seattle and one of the study’s lead investigators. "Most people would turn their MP3 player up at least a few decibels above the background noise, if not five or six. So now their exposure isn’t 80, it’s 86. And when we start getting up to sustained levels in the mid-80s that’s a concern because your recommended daily exposure duration is pretty short at those levels—less than an hour based on recommendations from the EPA."
That can be a problem considering how much time some Americans log on their iPods. We recently reported that most people listen at safe volumes in quiet settings. But once you put an MP3 user into a noisier setting, such as an airplane cabin, a coffee shop, or a city street, a large majority crank it up to risky levels. And a Consumer Reports online survey from 2006 found that 18 percent of users listened to MP3 players while riding mass transit.
Neitzel has also studied recreational exposures of young construction workers* and found that up to 20 percent had off-the-job noise exposures at levels that could pose a risk to hearing even in the absence of noise at work. The highest off-the-job exposures occurred during yard work, and while commuting in a car or bus.
Neitzel’s quick to note that the population he studied was entirely of young men who also had noise exposure at work, but nonetheless it’s not hard to see how similar exposures can effect other Americans. A nationally representative Consumer Reports survey from 2008 found that 70 percent of Americans who use a gas mower or leaf blower, never use hearing protection. Lawn and yard equipment typically ranges from about 86 to 99 decibels.
To get an idea of my own recreational risk I took a noise dosimeter, which measures the average decibel level of noise at the ear, to test my exposure. Here’s what I found:
My approximately 90 minute car commute from Brooklyn to Yonkers and back ranged from a low of about 70 decibels up to 82—and I don’t blast the radio to booming levels.
A trendy Thai restaurant in the Williamsburg neighborhood in Brooklyn ranged from about 81 decibels to 88, and lingered in the mid-80s for most of the hour.
Mid-day bowling at an eight lane, half-filled local alley hovered around 90 decibels. All of these sound levels are enough to contribute to noise induced hearing loss. And some of my colleagues found similar exposures during other recreational activities.
CR’s Take: Our health and safety experts, after studying existing guidelines and scientific research on hearing loss, have concluded that almost everyone can safely be exposed to 70 decibels without harm. But you should do everything you can to avoid or minimize exposure to noise above 100 decibels. As for the decibels in between, it all depends. If your hearing is already deteriorating or you are exposed to significant noise on the job or recreationally, try to avoid other prolonged exposure to noise between 75 and 85 decibels.
Above that, everyone should limit prolonged exposure or use hearing protection. For instance, if you're going to spend time operating a 90-decibel lawn mower, wear earplugs or earmuffs—not your iPod. Finally, when you are using your MP3 player, noise-canceling and in-ear headphones can help reduce background noise—and that can help commute a sentence of hearing loss from subway exposure.
—Kevin McCarthy, associate editor
For more on how to protect your hearing, see our report, Protect your ears from noise. And if you’re in the market for a hearing aid, don’t miss our hearing aids guide and lab tests of hearing aid features (subscribers only).
Image: dilworthdesigns; *links to PDF