During my September presentation on the safe use of landscaping equipment for the Massachusetts Professional Landscapers Association, we discussed the need for hearing protection due to the noise generated by some of the equipment used like leaf blowers, jackhammers, chainsaws, etc. At the end of the presentation, several attendees posed questions pertaining to the level of noise reduction afforded by earplugs and earmuffs. It can be confusing, so I would like to re-state and try to clarify that information using the example of my backpack leaf blower I showed in the presentation. Please note that the information below is for illustrative purposes only, as requirements and guidelines will vary depending on the specific equipment and environment in which they are used.
My backpack blower has a manufacturer’s label stating it has a noise level of 106dB. Per OSHA’s Permissible Noise Exposures chart below, I need hearing protection if I use the blower for just under an hour. Some of you mentioned that you have workers who use these blowers all day. So, how can you safely increase their duration of use?
Earplugs and ear muffs have a noise reduction rating (NRR) which is a measure that determines its effectiveness to decrease the sound exposure when properly worn. Earplug NRRs typically range from 22dB to 33dB and ear muff NRRs typically range from 20dB to 30dB. Unfortunately this is where the confusion sets in. The device’s NRR does not reduce the surrounding decibel level by that specific NRR number.
In the case of my backpack blower that creates 106dB, if I wear NRR 33 earplugs, my noise level exposure would not be reduced to 73dB. Instead, to determine the actual amount of noise reduction, I have to take my earplug NRR number, subtract 7, and then divide by 2. So that would be (33-7) ÷2 = 13 which is the decibel reduction afforded by my earplugs. So, 106dBA (backpack noise) minus 13dB (earplug reduction) gives me a new level of noise exposure of 93dB, which gives me about 5 hours of use per day per the OSHA chart above. So how can I get to the point where I can use that blower for 8 hours?
I can wear dual hearing protection, which means wearing earmuffs over the earplugs. But how does this affect NRR? Rather than adding the two NRRs together, I simply add 5 decibels of protection to the device with the higher NRR. So with my backpack blower, if I wear NRR 33 earplugs and NRR 30 ear muffs, I add 5 to the NRR 33 rating (the higher of the 2) and get an NRR of about 38, which reduces my noise exposure from 106dB to about 68dB – well below the level I need for a full day of use.
Remember that headsets and ear buds for listening to music have no NRR and provide no protection against noise so don’t permit them. Also, damage to hearing from high noise levels is permanent. Provide your staff with the proper level of hearing protection for the duration of their noise exposure, enforce its use, and teach them to wear it properly for maximum effectiveness.
Acadia Insurance policyholders can order free online videos on noise reduction, landscaping safety, and many other topics at www.Acadiainsurance.com under the Loss Control tab. The website includes instructions for ordering and for previewing the videos for content suitability.
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