MASTERING MANAGEMENT
Doubling up on Hearing Protection
SMITHFIELD, RI - Will doubling up or wearing dual protection – wearing an earmuff in addition to earplugs
- provide added protection against extreme noise levels? According to a new Sound Source bulletin recently released by the Bacou-Dalloz Hearing Safety Group, the answer is yes, but perhaps not as much as you thought.
According to Bacou-Dalloz, dual protection is not required by Occupational Safety & Health Administration (OSHA) regulations for general industry in the United States; it is required for mining operations governed by the Mine Safety & Health Administration (MSHA) for noise exposures more than 105 acoustic decibels (dBA), using the eight-hour time-weighted average. That said, the National Institute for Occupational Safety and Health (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.
However, there are also risks associated with dual protection. "Using earplugs and earmuffs concurrently seriously isolates the wearer," says Brad Witt, Audiology and Regulatory Affairs manager for Bacou-Dalloz’s Hearing Safety Group, "so it is warranted only in extreme noise levels."
He also suggests dual protection is overused: "When a high-attenuation earplug or earmuff is properly fitted and the user is motivated to use it correctly, some hearing professionals say the need for dual protection is rare."
So how much protection does doubling up provide? "That depends on the fit, but it is not simply the combined ratings of the earplug and earmuff. There is a ceiling effect that limits the amount of combined protection," explains Witt. The maximum amount of attenuation that can be attained by most people is 35j to 50 dB, depending on the frequency of the sound.
"The key to obtaining maximum benefit from dual protection is proper fit, especially the fit of the earplug,” says Witt. “When a poorly fitted earplug is worn with an earmuff, the resulting dual protection is little more than the earmuff alone."
As for a rule of thumb for estimating the effects of dual protection, OSHA recommends adding 5 dB to the Noise-Reduction Rating (NRR) of the higher-rated device. But this, says Witt, "sacrifices some accuracy. An earmuff typically adds about 4 dB to the NRR of a well-fitted foam earplug, and about 7 dB to a well-fitted premolded earplug."
He also says that an earmuff with moderate attenuation provides the same effect as a high-attenuation earmuff when either is worn over a well-fitted earplug.
(Source: Bacou-Dalloz Hearing Safety Group)
