By the time he retired this year on disability, he had lost more than a quarter of his hearing. The last straw came when he missed a turn on an emergency run - he didn't hear his officer's directions.

Just 43, Evers wears a $5,700 pair of hearing aids. He works part time with his brother-in-law at a garage door company, but he misses his old job as a firefighter, "the only thing I really ever wanted to do."

"If this would have happened to me at 55," he says, "it would probably not be that big a deal. But in my 40s ... "

Evers is one of many among the 75 million Americans born during the postwar baby boom who are discovering that their mothers were right - all that noise did damage their hearing.

Whether it was at rock 'n' roll concerts, between stereo headphones, on the job or on foreign battlefields, hearing experts believe millions of boomers have done permanent injury to their ears.

Now ages 41 to 59, increasing numbers are realizing they've lost sensitivity to high-frequency sounds - including those they need to distinguish among "th," "f," "s" and other consonants critical to understanding speech.

"It's perceived as, 'I can hear you, but I can't understand the words,'" says Dr. David J. Eisenman, medical director at the University of Maryland Medical Center's Hearing and Balance Center.

The problem is worst when there's lots of background noise, such as at parties or in restaurants. And hearing loss is often accompanied by a persistent ringing or buzzing in the ears, called tinnitus.

Hearing experts don't have studies to prove that baby boomers' hearing is worse than their parents' at the same age. But audiologists say more boomers seem to be seeking help earlier than their parents did.

"There's no question that baby boomers have been exposed to different sources of noise than any generation before them," says Dr. James F. Battey Jr., director of the National Institute on Deafness and Other Communication Disorders. "We're certainly seeing people in their 40s and 50s who notice their hearing is not as good as it used to be."

Montgomery firefighters now must wear ear protection. Sirens have been moved from fire engine cab roofs, where they were close to firefighters' ears, to the front bumpers.

The county's fire officials say five active firefighters are known to wear hearing aids. And a round of testing in June found 15 percent of the county's 1,038 fire fighters have some hearing loss - a third of it moderate to severe.

"I think it's much higher than that," says Kenneth M. Berman, a personal injury lawyer in Gaithersburg. He has enlisted 1,000 veteran firefighters - including 100 from Montgomery County - to join in lawsuits against Federal Signal Corp., one of the nation's largest siren manufacturers. Nationwide, nearly 2,500 firefighters with hearing loss have joined lawsuits.

Some hearing loss is normal with aging. A 1995 study noted by the Centers for Disease Control and Prevention found that more than one-third of men and 22 percent of women reported hearing impairments by their early 70s - proportions that rose to about half by age 85.

The problem is that noise-induced damage accumulates throughout life, piling on top of impairments driven by age or genetics.

A 1997 study of the elderly in Alameda County, Calif., found that the incidence of hearing impairment had doubled between 1964 and 1994.

"It seems pretty obvious that hearing loss is increasing, probably because of environmental noise," says William J. Strawbridge, a medical sociologist at the University of California, San Francisco and co-author of the study.

Sound intensity is measured in decibels. An increase of 10 decibels represents a 10-fold boost in power. Twenty decibels reflects sound 100 times more powerful. The impact on humans depends on intensity, duration and distance.

Charlie McCollum knows this well. He figures he lost about 10 percent of his hearing during the late 1970s, during three years of full-time work as a rock 'n' roll writer for the now-defunct Washington Star newspaper. He was in his early 30s then.

"As a critic, you frequently got seats that were inside a VIP area that was even closer to the banks of speakers than most audiences," he says. "The last full year I did it, it was 285 concerts. ZZ Top and Kiss and bands like that were probably doing 150 decibels."

Any sound above 85 decibels can damage hearing with long or repeated exposure. Above 125 decibels - about usual for a chain saw - safe exposure is measured in seconds.

"Suddenly, I realized I was not hearing people telling me things," he recalls. "I kept saying, 'Huh?'"

McCollum is now 57 and a TV writer for The Mercury News in San Jose, Calif. "I still have problems hearing out of my left ear," he says. "If I'm talking to somebody, if there's a lot of ambient noise, I have to be careful to point my right ear toward them."

The list of rock musicians with hearing impairments is long and distinguished, including Bob Seger, Jeff Beck, Sting, Eric Clapton, Peter Frampton and Bob Dylan.

Fans' ears may be naked, but many performers today wear custom earplugs to avoid the damage early rockers suffered, according to Kathy Peck, executive director of H.E.A.R., a nonprofit group working to prevent hearing loss among musicians, fans and stage crews.

As a bass player, singer and songwriter with The Contractions, a 1980s, all-women punk band, Peck was nearly deafened by loud music. She says fading bands often play smaller venues with the same sound systems they once used to fill stadiums.

"Why don't they just turn it down? I wish people would," she said. "It's like, you don't have to be that loud. A lot of times their hearing is shot."

Music played through earphones can damage hearing, too, especially when it's turned up for hours to drown out other sounds.

In April, a survey by Australia's National Acoustics Laboratories, reported in the International Journal of Audiology, found that 25 percent of headphone wearers stopped on city streets were listening at damaging volumes.

Just how does loud noise damage the ear? Scientists say we perceive sound when sonic pressure waves strike our eardrums, then pass through the structures of the middle and inner ear to rows of "hair" cells inside a snail-shaped structure called the cochlea.

They're not true hairs, scientists say, but they vibrate in response to the sound and dispatch electrical impulses to the brain. They can be killed by noise, infection, and certain cancer drugs and antibiotics. Like adult teeth, once lost, they don't grow back.

UM's Eisenman says some noise damage is probably physical: Violent vibrations, such as those caused by gunshots and explosions, simply destroy cell membranes.

By some accounts, nearly a third of the combat personnel returning from Afghanistan and Iraq are reporting significant hearing loss and tinnitus. "It's a big problem for the military," says Dr. Richard Salvi of the University at Buffalo's Center for Hearing and Deafness.

Nearly 300,000 U.S. veterans received disability payments for hearing loss in fiscal 2004. It is the single most common service-connected disability paid by the Department of Veterans Affairs. Tinnitus ranked third, with 290,000 veterans.

Of those receiving hearing-related disability payments, the VA says, 29 percent were Vietnam-era vets - largely baby boomers.

Scientists believe hair cells also succumb to "oxidative stress." Overworked sensory cells accumulate the toxic byproducts of metabolism faster than they can get rid of them, and the byproducts destroy vital cell structures.

While the damage is permanent, there is help for dwindling hair cells - the hearing aid.

"They're much better than they used to be," Eisenman says. Modern digital hearing aids can be tuned to amplify the patient's lost frequencies, boosting them above background sounds. Many also have built-in directional microphones that can pick up a conversation in front of the wearer while damping the rest.

Still "none of these hearing aids ... provides hearing as good as that we're born with," Eisenman says. And there is a persistent stigma attached to them, so people who need them often delay.

Evers wore his hearing aids on fire calls for four years. But off-duty, he took them off because he felt they made him appear disabled. "I thought people were staring at me," he says.

The most radical treatment for hearing loss is the cochlear implant, which converts sound into electrical signals and sends it to the auditory nerve. But it's generally reserved for people who are no longer helped by hearing aids.

Noise-induced hearing loss often comes with tinnitus, a ringing in the ears that drives some victims to distraction.

The sound isn't really coming from the ears, Salvi says. People whose auditory nerves are cut during cancer surgery still hear it.

Salvi likens it to the phantom limb pain experienced by amputees: "As we get more and more hearing loss, the brain turns up the volume control to try to hear the very weak signals coming from the ear."

Eventually, like a radio that's too far from the transmitter, all the brain hears is neural "static."

Some victims - perhaps three-quarters - simply ignore it. The others can't and may have significant distress. For them, doctors may offer counseling and a low-level masking noise that reduces the distraction of the ringing.

Researchers are also experimenting with gene therapy to improve the survival rates of beleaguered hair cells - or even to convert nonsensory cells in the cochlea into new hair cells.

In February, scientists led by Dr. Yehoash Raphael of the University of Michigan's Kresge Hearing Research Institute reported that they had restored partial hearing to guinea pigs whose auditory hair cells had been destroyed by chemicals.

Using a modified cold virus as a vehicle, they introduced into the guinea pig's cochlea a gene called Atoh1 that instructs undifferentiated cells in developing embryos to become hair cells.

Atoh1 worked in mature guinea pigs, too, stimulating nonsensory support cells in the cochlea to become new hair cells. Tests showed the animals recovered some hearing.

"It doesn't mean the hearing is good," Raphael says. And more progress is needed before any clinical trials in humans: Getting the genes into the human cochlea would require opening the skull.

Even so, Raphael says, it's "the first time anybody can take a deaf animal and give it back some hearing. We think it's a great start."

Until the right technology comes along, millions of baby boomers will continue to muddle through with muddled hearing. McCollum, the former rock critic, says he has resisted hearing aids, even though he misses some conversation.

"My hearing never got so bad I felt I wanted to go there, maybe out of vanity," he says.

But his wife has threatened to buy him an ear trumpet.

By Frank D. Roylance
http://www.baltimoresun.com/news/nationworld/bal-te.hearing04dec04,1,7182803.story?page=3&coll=bal-nationworld-headlines