Whuzzat?

As a boy, I enjoyed playing with fireworks. Cherry bombs, M-40s--they were all fine--the louder, the better.

As a young man, I was a member of several rifle teams, both small and large bore. Back then, it was not considered macho to wear ear protection.

In the Army Corps of Engineers, it was a positive delight to watch my platoon practicing blowing up bridges and creating road craters, all with a satisfying blast that made your ears ring. I'm paying for it now. My ears still ring and I don't hear very well.

Almost everyone experiences a buzzing or ringing in their ears at some time. A chronic condition, though, is enough to drive a person to distraction--it's like the smoke alarm in your house going off 24 hours a day.

Terry Dunkle, in the April issue of Science 82, provides some insights. The condition is called tinnitus (pronounced tin-EYE-tus). I can be caused by any number of reasons. Among these are ear infection, anemia, or simply a hair resting against the eardrum.

But the single largest cause is exposure to loud noises. Vibrations on the eardrum are transferred to a piston-like bone, smaller than a grain of rice, which concentrate their force on the inner ear in the same way that spike heels concentrate a woman's weight on a hardwood floor. The force is applied to the cochlea, a fluid-filled chamber with thousands of hair cells standing up inside like teeth on a comb. Vibrations of these hairs give the brain the information it needs to interpret the information as a tone.

Loud noises can cause these hair cells to be broken off or torn loose. This makes a person partially deaf to tones at the same frequency as that which caused the damage, and creates the ear-ringing, or tinnitus at that same tone. Hearing in the higher frequencies usually goes first. By age 40, most Americans have lost some hearing in their upper two octaves.

The amount of damage that is caused depends on both the loudness of the noise and the duration to which the ear is subjected to it. A power mower or motorcycle generate about 105 decibels--enough to damage some people's hearing in less than an hour. Rock concerts, discos, and some stereo headsets will go up to 135 decibels, the same as a jet engine. That is enough to rip off hair cells instantaneously. Also, a slap on the ear is not proper discipline for any child that you wish to hear you in the future.

Normally, a child with undamaged ears can hear a mosquito singing outside a window, when the eardrum is receiving less than one quadrillionth of a watt of power. Given a power mower, a snow machine, a chain saw, or a rock concert, however, and they lose part of the hearing they once had. I wish somebody had told me that.