You bought your Stihl, Homelite or Husqvarna chainsaw, you have used it a few times – now you think you need to get some hearing protection.
NRR, noise reduction rating, is a standard noise reduction “C” rated scale mandated by OSHA. The effect of noise on the human body is typically referenced to the “A” weighted scale. This is what should be used when comparing hearing protection devices. You can convert from the “C” scale to the “A” scale be subtracting 7 from each number. Each noise reduction device has a NRR rating. So you can find out its performance based upon your expected noise levels by subtracting 7 from the NRR, then subtracting that result from the dBA noise level that you expect to encounter.
A typical chain saw has a rating of 120 dBA. The earplug you are considering has a NRR of 29 – pretty good. The final noise value would be 98 dBA. Noise source 120dBA minus the 7 for the correction value minus 29 for the hearing protection value results in (120-29-7)=98, which is still dangerous and would only allow for a 2 hour exposure. If you use an ear plug with an RR of 33, the effective noise level gets reduced 94 dBA (120-33-7)=94, which would allow for a 4 hour exposure, to meet OSHA standards.
The duration of the sound levels that you encounter is important. Typically you will not be exposed to the maximum 120 dBA of the chainsaw for a full 4 or 8 hours a day- there is a lot of down time and operation at lower sound levels. The shorter the time you are exposed, the less the danger to your hearing. A few things to know:
* The sound does not have to hurt to damage your hearing. Exposure to very loud concert music for a few hours can cause tinnitus (a ringing or buzzing in the ear) that will affect you for the rest of your life. It can also reduce your ability to hear high frequencies. This will have a lasting effect on your music listening pleasure.
* Hearing damage is cumulative. It never repairs itself. A little damage from fireworks, plus a little from operating your stihl chainsaw and a little more from the rock concert, will slowly but noticeably impair your hearing.
* The louder the sound, the faster damage. If you are exposed to loud sounds make sure you either get away, cover your ears with your hands or put on hearing protection very quickly. Seconds count.