Will doubling up or wearing dual protection (an earmuff in addition to earplugs) provide added protection against extreme noise levels? The answer is yes, according to a new Sound Source bulletin from the Bacou-Dalloz Hearing Safety Group, but perhaps not as much as one thinks.
The bulletin, Sound Source #11a, “Dual Protection, is written by audiologist Brad Witt and is available at www.hearingportal.com/hearingconservation/hc-snd-ame.asp.
Dual protection is not required by OSHA regulations for general industry in the United States, but is required for mining operations governed by the Mine Safety & Health Administration (MSHA) for noise exposures over 105 dBA (8-hour time-weighted average). Similarly, NIOSH recommends dual protection for any exposures over 100 dBA, and some companies require it for employees with progressive noise-induced hearing loss despite normal protective measures.
So how much protection will doubling up provide? That depends on the fit, says Witt. The maximum amount of attenuation that can be attained by most people is 35-50 dB, depending on the frequency of the sound.
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