Noise-Induced Hearing Loss - What? Say Again?

I recently crossed paths with a motorcycling friend whom I hadn't seen in at least 10 years. It was great to see him and good to find that he was still very much into motorcycles. He told me that he commutes to work on a motorcycle almost every day (actually the only way to transport yourself in the sprawling gridlock of Los angeles) and still takes the occasional road trip to a distant destination on two wheels.

During the course of our conversation, though, I noticed that he asked me to repeat my statements every once in a while. We were inside an office building, so the environment wasn't noisy enough to cause problems. And while I'll admit that I probably mumble a word here and there, I haven't had any people tell me that I'm too soft-spoken. Mind you, it wasn't as if I was talking to an elderly person with a poorly functioning hearing aid or anything like that; it was just that his handful of "say again?" requests kind of stuck in my mind after our chat.

As motorcyclists we're bombarded with a lot more environmental noise than other motorists. And continued exposure to that noise can have harmful long-term effects on our hearing. Ironically some of the riders I started out with in my beginner years wore earplugs because their bikes were fairly loud at full bark, and the example they set (the earplugs, not the loud bikes) is one of the reasons I've worn earplugs literally from day one. But interestingly enough, the most damaging din isn't from the source you might initially think.

Back in 1994 two ear specialists from england conducted a hearing test on 44 Grand Prix riders to determine if they suffered from NIHL (noise-induced hearing loss). Almost half of them showed hearing losses much greater than the median for each one's age. "so what?" you say. "I'm not a GP rider." No, but note that this test was conducted in 1994, long before unmuffled MotoGp four-strokes ever made an appearance; muffled two-strokes with a 102-decibel-A (dBA) limit were the mount of choice back then. It was soon determined that the sound responsible for the riders' hearing loss was wind noise. And this was with the latest, trickest, most aerodynamic helmets, many with custom parts for each rider to ensure the best fit.

The two specialists, Andrew Mccombe and J. Binnington, then conducted a very thorough scientific study in 1995 of British street motorcyclists, including the country's motorcycle police. By inserting a tiny microphone next to the rider's ear they were able to measure noise levels accurately, part of which allowed them to determine that wind noise begins to drown out all other sounds once the rider passes 40 mph. At 100 mph, the wind noise level averaged at least 110 dBa for the 10 different helmets measured, which is about the same as listening to a gas-powered chainsaw (and this is with a helmet-imagine how loud it must be without one). Even cruising at 70 mph, wind noise would be about 100 dBa, which OSHA (the federal occupational safety and health administration) noise exposure standards state you can tolerate for a maximum of two hours per dayand that's cumulative, not per exposure-before permanent hearing damage definitely occurs. part of Mccombe and Binnington's study involved having a group of 18 selected riders go through a rigidly controlled test, and all were found to have suffered measurable hearing damage.

"Big deal," some of you are surely saying. "I've been riding for 10 years without earplugs and can hear fine." The problem is that the damage to your hearing is insidious; the most vulnerable parts of your ear are the receptors that handle the higher frequencies of sound that aren't readily noticeable. Everyone has surely experienced temporary hearing loss from deafening noises in the lower frequencies such as fireworks or loud concerts; after an hour or so your hearing returns, giving the impression that permanent hearing loss would involve the same massive deficiencies across the complete hearing frequency range. Unfortunately, noise-induced hearing loss from continued exposure occurs in a much more subtle way. The lost higher frequencies involve the minor inflections of speech that help define spoken language, especially consonants that don't have the louder vocal intonations of vowels, often occurring as the difference between past and present tense or singular and plural. For example, if someone were to speak in a normal tone of voice and environment, would you be able to tell the difference between "happen" and "happened" or "sportbike" and "sportbikes"?

I recall my friend was one of the macho types who felt that earplugs were an unnecessary hassle, and I have the distinct feeling that he may have been suffering from the cumulative effects of NIHL. Because wind noise occurs in the sound frequencies that earplugs are most effective at blocking, they can often reduce the sound level by at least 20 dBa, a very significant amount. Wearing earplugs may seem like a needless chore, but they can go a long way toward preventing you from being fitted up for hearing aids well before your time.