by David L. Hough

ECENTLY I WAS explaining over the phone to Alan Schade, "I guess I'm one of those oldtime bikers who just toughs it out. I carry earplugs mostly so I can get some sleep when the guy in the adjacent tent at the rally starts to snore like a chainsaw.'

"So, you don't wear earplugs when you're riding?" Alan asked.

"Naw, earplugs are just too much trouble. You have to remember to stick 'em in your ears before strapping on your helmet. And, on those rare occasions when I have remembered the plugs, it's always been a struggle to get them stuffed in. Then, after a few miles, that constant pressure in my ear canals is a distraction. But what's really disgusting is to pull out the plugs after a coupIe of hours and find them covered with slimy brown ear wax. Besides, l can still hear pretty well, even after 3O years of riding. So, mostly I wear the earplugs in my jacket pocket."

"I love tough guys like you," Schade retorted. "We'll be measuring you for a hearing aid within ten years."

Schade is an audiologist in San Clemente, California, and an experienced motorcyclist. Alan had heard through the grapevine that I was working on an article about hearing protection for motorcyclists, and phoned to see how it was going.

Truth was, the article wasn't going very well at all. Writing articles is sort of like taking a motorcycle ride. Sometimes everything goes smoothly, and the facts just unwind like a twisty backroad on a sunny Sunday morning. Then, sometimes

traffic gets aggressive, the engine sputters and the surface turns to mud. Frankly, I was spinning my wheels like a V-Max that had made a wrong turn downhill into a swamp.

At first blush, it seemed simple enough to write a little ditty about earplugs. I'd pored over a few books at the library, and connected with the audiology clinic at the University of Washington in Seattle. Professor James Labiak volunteered a brief explanation of how the ear works, showed me how the delicate nerve endings in the ear get damaged, described how hearing is tested, provided a list of technical articles about hearing loss and protection, and demonstrated his personal form fitted earplugs.

I hadn't realized the hearing business was so complex. There are hundreds of articles about noise levels of industrial equipment, woodworking machinery, chainsaws and jackhammers. There are pages and pages of information on noise measurement and hearing damage. OSHA noise exposure standards are easy to find. The amazing thing is, an audiology professor at a major university couldn't find anything specific about how all this relates to motorcyclists.

Are sound levels loud enough on a motorcycle to cause hearing damage? (We don't know.) What are the major sources of noise on a motorcycle? (We don't know.) Is wind noise around the helmet a significant source of noise? (It might be) What frequency is helmet wind noise? (We aren't sure.) For a motorcyclist riding in traffic, do other vehicles generate noises loud enough to be damaging? (We don't know.) Unless you know what noise levels and frequencies you are dealing with, you don't know if you even need hearing protection.

What Are We Dealing With?

Consider the 'loudness" of a motorcycle exhaust You can take a sound meter and hold it in back of the muffler a measured distance and rev up the engine. You'll get a reading on the scale. The typical sound meter is graduated in decibels (dB) on the A-weighted scale, or what the experts call dB(A). The (A) scale is fudged to mimic the sensitivity of the human ear. But the sound coming out of the pipe isn't just a single note, like f-flat on a trombone. It's a whole bunch of sounds, each with a different loudness and frequency, more like a rock band warming up. A Yamaha TZ creates more high frequency sound waves, while a Royal Star has more low-frequency soundwaves, even if both measure the same loudness on the meter. Now, answer this: At the same 41dB(A) level, which exhaust note would affect hearing the most, the screaming TZ, or the thudding Royal Star? More to the point, what's the level and frequency of noise in a rider's ear canals? And, where is the noise coming from?

The only way to answer such questions. Professor Labiak suggested, would be to take a motorcycle out in traffic and measure the noise with a device that would record actual sound levels and frequencies, both outside the helmet and inside the rider's ear canal.

Unfortunately, the U of W's "dosimeter" device was a huge beast too large, too ancient, and too valuable to be carried on a motorcycle. And even if we had a portable dosimeter of our own, we'd need to invent some foolproof tests.