A well-fitted earplug or earmuff is enough to protect workers against noise exposure in most industrial environments today. However, when noise exposure exceeds the capabilities of traditional hearing protection, employers need to take special measures.
In environments where intensely loud noise can't be controlled at the source, it might be necessary for workers to wear earplugs and earmuffs at the same time – often referred to as "dual hearing protection" or "double hearing protection."
Typically, dual hearing protection only is appropriate for extreme situations, when noise exposures in the workplace exceed 105 dBA time-weighted average (TWA). In fact, under 30 CFR Part 62, MSHA requires dual protection in such circumstances. NIOSH supports a more conservative approach, recommending a combination of earplugs and earmuffs for exposures over 100 dBA TWA.
Dual hearing protection also can be a viable option for users who want extra protection or wish to reduce the annoyance of background noise. But a note of caution: When workers have more protection than needed, it can hinder their ability to communicate and detect warning signals.
The Basics of Dual Protection
The first step in choosing dual hearing protection is to select a well-fitted, quality earplug. The earmuff adds extra protection, but the style and type of earmuff have less impact on the resulting combined noise reduction. Adding an earmuff over an earplug usually provides a bigger boost in attenuation for low-frequency (pitch) sounds. Overall added protection is about 4 to 8 dB, a significant increase. The OSHA Technical Manual specifies adding 5 dB when evaluating dual hearing-protector performance.
Despite the extra protection provided by dual hearing protection, employers also need to consider potential obstacles. Most notably, wearing two hearing protectors simultaneously can be uncomfortable. As mentioned earlier, too much protection can interfere with communication and situational awareness, making the worker feel isolated or unsafe.
No matter how high the protection rating, there's little benefit if employees fail to wear the hearing protectors consistently and correctly.