One thing I have read is that it is impossible to get above about 36 dB NRR with standard muffs or earplugs and anyone who claims this is lying because the structure of the human head will transmit sound above these levels through the skull around the muffs or plugs. To achieve >36dB the head has to be completely encased in a lead helmet or similar.
So where would I find such a safety helmet? I'm kidding LOL