Do You Hear What I Hear?

And when I mentioned the project to Bob Gerend at Ural America, Bob helped track down a former associate at the Boeing Acoustical Lab, an engineer who just might be willing to loan a portable dosimeter to the University for a few days.

Then, in the wee hours one day before Kevin and we're to get serious about our research, the telephone beeped me awake.

Doctor McCombe was on the line from. Frimley Park Hospital in Camberley, England, where he is now a Consultant ENT Surgeon. McCombe explained that my letter had wandered around the UK awhile before finding his current address. Yes, he and his associates had done the studies that answered our questions. What's more, these were professionals who had taken pains to make sure all the research was done right. McCombe had already mailed me some reprints. Now we were getting somewhere! If McCombe had already done the research, there was no sense in reinventing the wheel. Hold the UW research, Kevin! Forget the dosimeter!

Keep checking the mailbox!

What's It All About, Alfie?

With the British studies finally in hand, I had some reliable information to help make sense of everything. But before we get into the details, let's first review how the ear works, just to be sure we're all playing off the same sheet of music. Then we can look at some numbers from the various studies, and finally consider how to tell if you are experiencing hearing damage.

It's Just a Generator

Like most parts of the human body, the ear is a bit more complex than it looks from the flabby side. Those big skin funnels just help focus sound waves into the ear canal, down to the eardrum. The eardrum wiggles a set of tiny bones in the middle ear that mechanically amplify the movement and transfer the vibrations to a snail-shaped cochlea that translates vibrations into electrical nerve impulses to the brain (Figure 1).

Sloppy testing isn't worth much, because you may not get reliable answers. For example, it's pretty tricky to get sound level readings on a motorcycle, because the microphone itself is hanging out in the breeze, and generates its own air turbulence that makes noise. That's why a tiny dosimeter probe inserted into a rider's ear canal is more accurate than a microphone taped on the helmet. I began to get that uneasy feeling that this article was slipping even further backwards into the quicksand, Hey, I didn't want to do a university thesis on the subject, I just wanted to provide reliable advice to the readers of MCN!

Even while the search for technical information went on, I'd been scrutinizing fellow motorcyclists, asking nosy questions of those who removed earplugs when they stopped nearby. I wanted to get some idea of how many motorcyclists wear earplugs, and their personal reasons for wearing them. The majority of motorcyclists don't use earplugs. Those who do, wear them mostly to cut down helmet wind noise so they can concentrate on their sport riding. Few motorcyclists I talk to seem to be concerned about hearing loss. Like me, they just haven't thought much about it, and haven't figured out how easy it is to damage0 your hearing on a motorcycle.

Well, maybe the earplug manufacturers would have some useful advice. Poring over the stack of research papers Prof. Labiak had provided, I noticed a lot of articles by the Cabot Safety Corporation in Indianapolis. Cabot is the company who started making those little yellow foam E.A.R, earplugs we used to wear on missions to the Boeing flight line. Its most prolific author is Elliott H. Berger, a Senior Scientist in Auditory Research. Berger was kind enough to reply to my letter, and provided a list of articles specific to motorcyclists.

Now I was finally getting a little traction. One big surprise from Berger's list was a reference to "Now Hear This: No Matter How Quiet Your Bike's Engine, Motorcycling is a Noisy Sport" by C. Coleman in (guess where?) Road Rider magazine, May, 1991. Somehow I'd missed it. BINGO!

Another name appeared several times: A. W. McCombe in England. McCombe and several associates had done a number of studies about motorcyclists and noise, answering such questions as "Do earplugs make it more difficult to hear warning signals such as emergency sirens?" A letter to McCombe was drafted and dropped in the mailbox, but many weeks went by with no response from England.

As I continued to dig around for more information, Peter Fassnacht (an MCN contributor) James Tangorra and Albert R. George had done some wind tunnel tests on motorcycle helmets at Cornell University to measure noise levels. The Cornell study answered some questions about wind noise levels around helmets, but didn't say anything about other noise sources and sound levels an a bike being ridden in traffic. But an added bonus of the Safety Conference book was discovering an article from Germany about relative noise levels of other vehicles on the road.

Without any solid data about real-world sound levels on the road, there were still a lot of unanswered questions. Labiak suggested that one of his Masters students was a motorcyclist who might be interested in helping with some research, if I could do the leg work to borrow a dosimeter and convince the owners we could return it unscathed. UW audiology student Kevin Frank offered to help, even after I made it clear that neither MCN nor I were in a position to cough up any grant money.