What is the effect of dual protection? (Use of both earmuffs and earplugs).
This is a commonly asked question, and the answer is somewhat surprising. If you use an earmuff with 29 dB NRR and an earplug with 29 dB NRR, the estimated protection is 32 dB. The physical energy of noise doubles with every three decibels. This is a physical fact. So if you place two machines producing 90 dB of noise, next to each others, you will end up with a noise level of 93 dB. In the same manner if you double up protection you will gain 3 dB.The above is an estimation, and both protectors have to be used correctly to achieve this result. We have actually seen laboratory reports indicating that as much as 6 dB can be gained from combined hearing protection. However, in real life situations, it is probably safe to assume 3 dB.
