A Little Bit Louder, Please

The National Institutes of Health runs a campaign against noise-induced hearing loss, called "Wise Ears," that emphasizes basic steps like wearing earplugs when operating power tools and moderating the volume on personal listening devices. The ubiquitous music players, which send sound directly down the ear canal, are a potential problem for millions of Americans, young and old. In a recent informal study at the House Ear Institute, researchers found that the new generation of digital audio players, with their exceptional clarity, allow listeners to turn up the volume without the signal distortion that occurs with traditional analog audio. Without distortion, which serves as kind of natural volume governor, listeners may be exposed to unsafe sound levels without realizing it. In preliminary observations, the music at the eardrum topped 115 decibels. Exposure to noise that loud for more than 28 seconds per day, over time, can cause permanent damage.

Kathy Peck, who learned the hard way about the dangers of loud music, has dedicated herself to helping other musicians avoid her fate. Along with Dr. Flash Gordon, the physician from the Haight Ashbury Free Clinic who helped with her hearing loss 20 years ago, Peck cofounded Hearing Education and Awareness for Rockers (HEAR). Since its inception in 1988 (with seed money from the Who's Pete Townshend, whose hearing was also trashed by loud music), the group has helped thousands of young rockers, distributing free earplugs at clubs, concerts and music festivals, and providing free screenings by audiologists.

For more than 6 million Americans, hearing aids are the best available solution for everything from mild to profound hearing loss. Today's digital devices, like the analog instruments that preceded them, amplify sound and transmit it down the ear canal to the eardrum. But the similarities end there. Thanks to digital technologies, modern aids offer better sound quality (above). Top-of-the-line models feature "directional" or "high definition" hearing. These devices use two microphones and an algorithm to enhance sound coming from the front (the person you are talking to), while tuning down sound coming from behind (the rest of the noisy party).

Despite such encouraging technical advances, there are about 21 million people in the United States who could benefit from hearing aids, but don't use them. Many simply can't afford them. Their costs range from a few hundred dollars for a basic analog device to $3,500 for high-end instruments, and are rarely covered by insurance. Another reason some folks eschew aids is discomfort--they simply don't like the feeling of walking around with a plugged ear canal. And even with digital technology, people can still have difficulty separating speech they want to hear from the background noise, a common hearing-aid problem. Yet another obstacle to wider use is stigma--many people associate hearing aids with aging, Slattery says, and would just as soon cup a hand behind their ear. "They're afraid to look old, but they don't mind looking dumb."

A new generation of implantable and semi-implantable hearing aids, currently being developed and tested, could solve many of these problems. Unlike conventional aids, the new devices transmit sound vibrations directly to the bones in the middle ear, bypassing the eardrum and improving speech perception. "You can amplify the higher frequencies without feedback problems," says Slattery, "and that gives a richness to the sound. It's the high frequencies that help you localize sound and hear better in noisy situations." Other pluses: no clogged ear canal and no visible sign of infirmity. But until insurance companies start paying for hearing aids (they are under increasing pressure to do so), the $15,000-to-$20,000 devices--intended for those with moderate to severe hearing loss--will remain out of reach for most.

A more permanent solution to hearing loss--regenerating damaged cochlear hair cells--is the shared goal of a scattered band of researchers around the country. Unlike birds and other lower vertebrates, which can regenerate hair cells, humans and other mammals get one set, and that's it. If scientists can discover a way to grow new hair cells in humans, exciting new treatments could be devised. Already, researchers at the University of Michigan have used gene therapy to grow new hair cells in guinea pigs. At the House Ear Institute, Andrew Groves and Neil Segil are studying the embryonic development of hair cells in genetically engineered mice. If they can unravel the process, figure out how it starts and why it stops in mammals, they may eventually be able to reactivate the cells and have them make new hair cells. In a related experiment, they have managed to coax some embryonic cochlear cells in mice to restart and become hair cells. "This is new stuff," says Segil, with the calm that often masks excitement in scientific circles.