Oct. 6, 2009 -- Convertible lovers who take to the open road with the top down may be risking hearing damage, according to a new study out of the U.K.
"If you are exposed for long periods above 85 decibels [of sound], you have the potential for hearing loss," says Philip Michael, MD, an ear-nose-throat surgeon at Worcestershire Royal Hospital in Worcestershire, U.K., and the study's lead author. In his study, he found that the noise level with the top down was higher than 85 decibels. "The maximum noise was at 70 miles per hour and that was 89 decibels. It has the potential for causing long-term hearing loss.''
To put those decibel levels in context, a normal conversation is about 60 decibels; a rock concert is about 115 decibels.
Michael is slated to present the study -- which was funded by the Worcestershire Royal Hospital -- at the American Academy of Otolaryngology-Head and Neck Surgery annual meeting in San Diego.
Testing Noise Exposure
Previous research done by others about motorcyclists' noise exposure, coupled with his own love of convertibles, prompted the study, Michael tells WebMD. Motorcycle riders tend to wear earplugs, he finds.
But the topic of noise exposure to convertible drivers has not been studied much, he says. So Michael solicited convertible-driving friends who donated six cars. Another car -- a Morgan plus 4 Roadster -- was borrowed from the car company. Then Michael and his co-researchers measured the noise exposure to a single driver driving seven different convertibles at 50, 60, and 70 miles per hour.
The cars tested were:
- Toyota MR2
- Mazda Miata MX5
- Audi A4 Cabriolet
- Morgan plus 4 Roadster
- Porsche 997 Carrera
- Aston Martin V-8 Vantage
- Bentley convertible
"We measured the nose by the driver's ear,'' Michael says. Noise by the driver's right ear -- the roadside ear, in the U.K. -- was measured for one minute with a sound level meter as the cars were driven at 50, 60, and 70 mph with the windows lowered and the top down. They also measured the noise exposure with the windows raised but the top still down when the cars were driven at 70 miles per hour.
When driven at 70 mph, the noise averaged 89 decibels, Michael found, with not much difference among the cars, which ranged from moderately priced to extravagantly priced. ''The car price didn't matter," he says.
The size of the sample was too small to perform statistical analysis, Michael notes, but he did find a general trend toward increased, although minimal, noise exposure with speed.
Noise Reduction Remedies
Putting up the windows -- never mind how geeky some feel that looks -- can cut noise exposure, Michael says. "If you have the top down and put the windows up, it drops the average to 84 decibels'' for five of the seven cars, he says.
Putting up the wind guard on the car may reduce noise, too, Michael says. Earplugs would help, too, he says.
Another idea is to carefully choose your top-down driving location. ''Mainly the problem is with highway driving," he says, as that is a higher-speed environment but also often has heavier traffic than city streets or rural roads, which adds to the noise of the wind and the car noise.
Two audiologists who reviewed the study results for WebMD call the research interesting and say it couldn't hurt for convertible drivers to exercise some caution for their hearing health.
So do the study results suggest there is reason for concern? Yes, says Alison Grimes, the head of the audiology clinic at the University of California Los Angeles Medical Center and assistant clinical professor of head and neck surgery at the David Geffen School of Medicine at UCLA. "I would qualify that by saying if you drive eight hours a day, seven days a week you have a much greater concern than if you drive two hours on a Sunday afternoon."
Rolling up the windows, as Michael suggested, is an option, Grimes says. "Anything you can do to put up a barrier between you and the sound."
The research, she says, "is sort of a reminder that noise comes from sources we don't even think about."
Driving your convertible with the top down, she says, "is a little bit like eating unhealthy food. You can do it occasionally, but don't go overboard. There are unintended consequences you don't want to deal with.''
"I think people should be cautious," says Debbie Abel, an audiologist in Poway, Calif., and director of reimbursement for the American Academy of Audiology. She says she has noticed more drivers putting the convertible top down and the windows up.
If drivers are considering earplugs, Abel suggests they first check with their state's motor vehicle department to find out whether they are permitted by law.