It is now officially fall and it’s the start of another maintenance season on the Trail.  I can almost smell the newly mown grass and hear the whine of chain saws and powered brush cutters. And speaking of hearing, here’s a few facts you might find interesting.

140 decibels – pain threshold

The amount of time you are exposed to the noise is also a factor.  The OSHA rating above is based on an 8-hour exposure, which during trail maintenance use most of us will never approach.  But it does give us a good baseline in selecting our hearing protection.  Also, keep in mind that most of the time you will not achieve in practice the advertised level of protection because to achieve that rating the ear protection must be fitted perfectly and that just does not often happen in the real world. So use ratings only a guide.

Ear protection products use a standard measure called the Noise Reduction Rating (NRR) which measures the sound blocking capability of each product.  NRR is a "C" rated scale mandated by OSHA for workplaces in the U.S.A., but to accurately determine the effects on human hearing, an "A" weighted scale should be used. To convert from the "C" scale to the "A" scale, just subtract 7. To determine the results to expect from an ear plug, first subtract 7 from the NRR then subtract that result from the dBA (average noise level from which you need protection). For example the noise of a chain saw at 120 dBA would be reduced to 98 dBA by an NRR 29 plug (120-(29-7) =98), which is still moderately dangerous, especially over several hours.

Silicone ear plugs are also common and mold better to the inside of your ear.  However, you should read the label carefully because different models run from about 21 NRR up to 33 NRR.  Make sure you get some at the higher end of the range, not the lowest.

Ear muffs are another common form of hearing protection.  Some models attach to your hard hat and can be folded back or up out of the way.  They are certainly harder to loose in the woods.  Muffs range from about 21 NRR to 35 NRR.  So again, you need to read the labels to make sure you are getting the protection you need.