Oct 6, 2014

#76 Hearing Damage and Motorcycling

All Rights Reserved © 2008 Thomas W. Day

It's tough to talk about technical things without technical language. So this article is going to be burdened with technical terms and other debris that can't be avoided. If thinking makes your head hurt, you may want to move on to another page.

A lot of motorcyclists suffer from tinnitus; "a noise in the ears such as ringing, buzzing, roaring, or clicking." My generation, the Boomers, is experiencing a higher rate of hearing damage than our parents suffer at their more advanced age and the generation following us is even worse hit by hearing loss. The reason is noise exposure.

You may wish to blame sinus infections, being dropped on your head as a baby, or bad luck for your tinnitus, but the real reason is probably your long term exposure to excessive noise. Even worse, your tinnitus was probably caused by exposure you could have prevented if you'd have cared about your hearing when you were younger. "If I'd have known I was going to live this long, I'd have taken better care of myself," sayeth (said-eth?) vintage rocker Al Kooper.

Motorcycling is a particularly abusive activity, as far as your hearing is concerned. If you are one of the "loud pipes save lives" crowd, you are probably a charter member of the "what did you say" group. Even by OSHA's conservative, obsolete, and employer-friendly standards, the kinds of noise levels we expose ourselves to riding motorcycles is beyond the harmful levels and into the "are you crazy?" territory. Good old mommy OSHA only grants our employers a "maximum allowable duration per day" of 1/2 hour at 110dBSPL (Sound Pressure Level) before hearing protection is required. OSHA "weights" that noise level with an "A-filter," which reduces the measured low and high frequency content, which would be appropriate for low level signals (under 55dBSPL unweighted) but is an improper use of the filter for high level signals. The original 1940's source for the OSHA standards, NIOSH (National Institute for Occupational Safety and Health), has continued evaluating this hazard and now says that "exposure for any duration" to sound pressure levels above 106dBSPL (unweighted) "may pose a serious health risk"

Inside a full face helmet, behind a moderate windshield, at 70mph, my noise measurement equipment says that I'm exposed to about 110dBSPL (C-weighted or mostly-unfiltered, for the technically inclined). These numbers have been confirmed by other test and measurement sources, but you're welcome to test your own gear. I'll even help if you don't mind riding your motorcycle for a few miles with small microphones stuck in your ears. Riding without a helmet and without hearing protection exposes your ears to sound pressure variations very near the levels of the loudest rock and roll concert you've ever attended; add loud pipes to that and you are probably venturing into uncharted territory.

The folks with the biggest noise exposure problem are probably those who ride big twins. After stripping off the manufacturer's already noisy pipes, these riders often add chrome exhaust farkles that boost the bike's low frequency (LF) noise output substantially. This, supposedly, compensates for the lack of actual power with the illusion of power; more noise. The problem with low frequency (below 150Hz) signals is that they pass through most acoustic obstacles (including your head) relatively unattenuated. Those LF signals cause all sorts of hearing mechanism damage. If this wave motion is strong enough (the signal is loud enough), it rips the cilia (hair-like structures inside the cochlea) from the inner lining causing loss of sensing at the frequency band previously measured by that cilia. Maybe more often, the noise just "flattens" those sensors so that they are less sensitive. This loss of sensing results in a neurological feedback loop that causes tinnitus. If enough cilia are damaged, you may hear a constant roaring or multiple ringing tones. Pete Townshend (songwriter and guitarist for The Who) described his tinnitus as having progressed into sounding like a constant "loud metallic waterfall." Your tinnitus may not be that bad, but it could get worse.

If you're looking to blame someone else for your tinnitus, you are a true American. However, you're probably stuck with either your parents to blame or yourself. The overwhelming majority of hearing defects are noise-related, but some of us have inherited our hearing sensitivity or defects. A life of sinus infections is probably not the cause of tinnitus, but the allergy medications you've taken could be. Other medications can also cause hearing damage and tinnitus.

Lots of us suffered hearing loss from 1960-70s pre-OSHA industrial noise exposure and some of us added to that with motorcycles and music and other bad habits. The problem with trying to overwhelm your tinnitus with more noise is that you are causing more hearing damage and even more tinnitus. I sympathize with that maddening noise you’re hearing, but trying to kill it with noise is self-defeating. If that constant noise bothers you during a distracting activity like riding, how do you sleep? If you move that constant noise from background to the loudest thing in the room won’t that be much worse? Eventually, you'd think that we might begin to pay attention to Al Kooper's warning about taking better care of ourselves in case we have to deal with the consequences later.

In the last decade, there have been a lot of studies on noise and biological noise effects. I don’t think this is something we should take lightly. We (as motorcyclists) are on the leading edge of a coming noise pollution reduction movement. In many urban areas, motorcycles are one of the most identifiable and prominent noises. Noise is making us, as a country and species, dumber and less civilized. Lots of countries are realizing this and attacking noise sources with science and legislation. Sometimes I suspect that in the US we may be too damaged to make much progress on this front, but that isn’t a good thing for our future.

On a personal level, I think you should consider wearing hearing protection when you ride (regardless of your exhaust output) and I would be very cautious about the noise levels you are suffering when you listen to music while you ride. If you wouldn't listen to music at that volume in your living room, you shouldn't be putting up with it while you ride. My wife's argument is "if it hurts to hear, it hurts your ears." Like most of our critical organs, the sensitive parts of your hearing are not repairable. If you overuse it, you will lose it. That is true for political clout, too.

MMM October 2008

All of the stuff that is technically correct in this article was thoughtfully edited and amended by Sarah Angerman of the University of Minnesota's Speech-Language-Hearing Sciences Department. All of the errors are my own.

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