Hearing for life.

At age 50 you can have extraordinary health: chiseled muscles and washboard abs; fast, limber legs; a cholesterol level of 90; a hearing aid in each ear...

What?

Permanent hearing impairment may be the price that many people are paying for physical fitness and entertainment. There are no refunds. Most individuals -- even health enthusiasts -- ignore warnings by the Occupational Safety and Health Administration (OSHA) that prolonged exposure to excessive volume (more than 90 decibels) can cause permanent hearing loss. The decibel is a unit of sound volume,

"I've been in places where I've said to people, `You need to wear earplugs,'"' says Christine Gerhardt, certified audiologist (hearing specialist) for the Family Hearing Center in Boulder, Colorado. "I've given them my card, and they look at me like I'm crazy."

Between the boom boxes in aerobics classes, loud car stereos, weight lifters carelessly banging around metal weight plates, roaring music at nightclubs, and screaming crowds at sporting events, "the hair cells in the cochlea are being assaulted by a constant bombardment of sound," Gerhardt says.

The cochlea, a fragile, spiral-shaped structure deep within each ear, is home to about 30,000 nerve cells that receive sounds from the environment.

* High-fidelity amplified music -- be it rock or classical -- from a boom box can pound as high as 110 decibels.

* Only 15 minutes of exposure to 115 decibel sounds can cause permanent hearing loss.

* One hour is the limit for exposure to 105 decibel sounds (typical aerobics class music) before permanent hearing impairment can occur.

* The volume is at least 85 decibels if a person must speak louder than usual, strain to understand speech from five feet away, or ask people to repeat statements, or if a person experiences ringing or pain in the ears.

No amount of exercise or vitamin supplementation will protect against noise-induced hearing loss (NIHL), which afflicts some 10 million Americans, many under age 40.

Cumulative Damage

"Hearing loss usually occurs very slowly," Gerhardt says, "and we are often very unaware of it as it progresses. Once you have hearing loss, there's no way you'll recover. Right now there is no way we know of to regenerate the nerve cells."

Humans are born with a hearing fund to which no deposits are made, but from which NIHL makes withdrawals. Like sun damage to the skin, NIHL is cumulative. It begins at high frequencies, initially undetectable. Over time the ability to clearly pick up lower frequencies (human speech) becomes impaired.

Many people don't worry about volume under 100 decibels, especially if they're exposed to it for less than one hour. But Gerhardt says, "Even if it's 85 or 90 decibels, that doesn't mean it's not going to damage your hearing," especially if the exposure is repeated over a long period of time. "You don't know if you're one of those people who's going to have hearing loss."

Similarly, not everybody who gets sunburns during childhood will develop skin cancer later on. However, a person won't know whether he or she has the propensity for hearing loss until it's too late.

The nerve cells in the ear never toughen up to loudness, though many people -- including people who rev up their 100-decibel motorcycle engines and tear down the street -- claim that the volume no longer hurts.

"Those preferring loud music and who have acquired a hearing loss mistakenly believe that their ears have acquired an immunity to damage," says Gary J. Glascoe, Ph.D., associate professor of communicative disorders at the University of Wisconsin -- Stevens Point. "Even an ear having significant hearing loss can continue to sustain damage in the presence of significant levels of noise ... even if the person can't hear the noise anymore."

The presence of NIHL does not prevent further hearing loss any more than jumping on a sprained ankle prevents further injury to the ligaments!

Difficult Detection

Many people believe their hearing is normal. NIHL can be difficult to detect under normal conditions, such as chatting with friends on the porch. How well can they decipher conversations from across a noisy room or words from over the phone in that same room?

"They can't see what is happening when they look in the mirror," Gerhardt says of health club patrons. "They can see their muscles, but they can't see what's going on in their ears. People who are exposed to noise over 85 decibels will at first experience a temporary threshold shift [transient hearing loss resulting from loud volume]. With repeated exposure, a permanent hearing loss can develop; it usually takes years."

Perhaps typical gym patrons, concertgoers, and loud-motor addicts have built up a tolerance to increasing amounts of potentially dangerous sounds.

Fitness enthusiasts claim that loud music motivates them, and men usually associate loudness with being macho: Tim Taylor on the TV series Home Improvement sure does! Motivation for exercise should arise from the quest for physical fitness, and hearing loss never makes a man more virile.

When the nerve cells die, they don't send pain signals to the brain. A weight lifter, with -- figuratively -- 20/40 hearing, works out in a roomful of loud, clanking metal. This individual may have no idea that three years ago his or her hearing was 20/20.

The same applies to people who frequent movie theaters, with their surround-sound systems that amplify on-screen explosions and gunfire. is the temporary entertainment worth the possibility of permanent damage? Let's not forget the dozen or so big, blaring TVs at sports delis, combined with loud music and scores of people yelling for their favorite teams!

"Significant levels of impulse noise (sudden intermittent loud noise) injure the ears more than the same level of continuous noise," Glascoe says. "Body-building gyms reeking of constant impulse noise -- metal-against-metal banging of weight plates -- can be more injurious than excessively loud music."

Some sources of harmful volume cannot be controlled with a dial, such as jackhammers and newspaper printing presses, But many other sources can: by the person in charge (health clubs, nightclubs, movie theaters, etc.). Thirty people repeatedly scream in unison in karate classes because the instructor commands, "Louder!" And military sergeants shout only inches away from cadets' faces (100 decibels). They yell back, and he sneers, "I can't heeeeear youuuu!" Maybe he has severe NIHL!

Staying home like a hermit is not the solution. Like the second-hand smoke controversy, nobody has the right to impose bad health habits upon others. Ironically, the scream-happy karate expert whose hearing is too dull to detect the thug creeping up from behind may end up getting bonked on the head!

Custom-made earplugs (which subdue only about 15 decibels and are available at hearing-aid centers) are one option (for volume under 100 decibels), but they can be uncomfortable. And how many military sergeants will permit their recruits to wear them?

Another option is bulky industrial earphones, available at hunting, gun supply, sporting goods, and hardware outlets. Muffling 25 to 29 decibels, they attract attention and are uncomfortable. Imagine the reaction if a person were to don earphones at a football game (110-decibel cheering).

What, then, is the solution?

Though 50,000 people at a ball-game aren't going to give up loud cheering, the volume at gyms, nightclubs, movie theaters, iceskating shows -- and even the amplification of microphones at high-powered business conventions -- can be set below 85 decibels, determined by an audiologist with a sound level meter. People will adjust, just as they have to skim milk, low-fat dressings, and no-smoking rules.

People who protect their hearing to prevent NIHL do not have "sensitive" ears. If the volume is uncomfortably loud for them but perfectly fine with others, the individual probably has very keen hearing and is able to pick up a wider frequency range than the others.

For example, many people will slather on smelly sunblock after reading just one article about the hazards of excessive sun exposure. This doesn't mean they have "sensitive" skin; they simply wish to retain its youthful structure.

Glascoe says, "Most of the older patients I fit hearing aids to acquired their hearing loss when they were younger."

A 75-year-old jogger should be able to hear every sound: from birds and rustling leaves and the laughter of distant children at play, to the child calling after him from 100 yards away because the prowler is outside his house.

"Our society has done much to warn us about impending danger to vision, but is still struggling to convince the populace that hearing can be injured also," says Glascoe. "The eye begins to hurt after looking at the sun for a moment. When exposed to loud sounds, the ear only rings. Does this follow the old adage that says only the wheel that squeaks the loudest gets the grease?"

The microscopic hair cells deep within the ears are just as important to our hearing as the retinas of our eyes are to our vision.

Helen Keller once remarked that vision loss separates an individual from mere things, but hearing loss separates that person from the community.

"Loneliness is a huge problem when one becomes older," Glascoe says. "Why would someone willingly jeopardize the one sense that forms connections with other people?"