The foam earplugs used correctly have better noise blocking than most other ones including muffs. If you want the most protection use the foam earplugs and ear muffs. I do that when shooting the really loud ones and will not shoot the 50BMG without both. Burn 217gr powder behind a 750gr bullet and it is loud with a break on the rifle.
Not associated or recommend these folks but they do describe NRR pretty good. https://www.coopersafety.com/earplugs-noise-reduction
Not associated or recommend these folks but they do describe NRR pretty good. https://www.coopersafety.com/earplugs-noise-reduction