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Realizing that this is a rather old thread at this point, it's still worth noting a few things.
First, if foam plugs and virtually ANY set of muffs are insufficient then nothing will be sufficient. It's literally impossible.
Second, have you seen the "bone conduction" headphones? These work because sound that originates outside your head can travel through the bones of your skull to your ears. This sound basically can't be attenuated. It's a complex issue, yes you can cover more bone and get more attenuation but at some point you're literally wearing a helmet.
Third, NRR ratings don't stack mathematically, at least by addition. If you are wearing plugs rated at pretty much the highest possible rating (33) and muffs at the same rating, the combined NRR isn't 66. OSHA (29 CFR 1910.95 and 29 CFR 1926.52) recommends adding 5db for the second set of protection, so 33+33 becomes 38, at best.
It's also worth noting that OSHA has a formula for "real world use" that indicates an actual protection level of less than half (subtract 7 and divide by 2) so 38 becomes more like 15-16.
The short answer is, if muffs and plugs aren't cutting it, you're in dangerous noise territory and there's really nothing more you can do except don't be in that noise level.
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