My ears are about gone. Had a thing called "sudden sensoneural hearing loss" no cure. Ended up with a specialist Otologist/Neurologist in Houston. He was one of the Doctors that invented the cochlea implant and traveled the US teaching other specialist how to do them. He is an avid shooter and has written many papers and research thesis on noise induced hearing loss.
A really intelligent man that basically saved me from deafness. He gave me some good information that He learned in his research.
He recommended the Howard Leight foam plugs that are NRR 33. They must be installed correctly. He cautioned me on "custom plugs" as he said that your inner ear canal is basically composed of cartilage and can change in dimensions daily due to water content in your body, body temp. etc. He explained that custom formed plugs may fit correctly one day but not another as your ear canal changes.
He did lots of research for the Navy as the loudest environment is the flight deck of one of our carriers.
He also cautioned me that the mastoid bone (behind your ear)can almost transmit the same decibels of noise to your inner ear as the ear canal and that only muffs large enough to cover the mastoid bone can really help with that.
He also said a shooter should train themselves to always pull the trigger with your mouth closed as an open mouth can allow sound to travel to the inner ear by the jaw bones and the Eustachian Tube.
He said, unless using a suppressor, all shooters should use double protection when shooting anything other than a .22 rimfire.
He said, however, that using both plugs and muffs does NOT double the NRR protection and that it will only add plus 5 NRR above the highest rating of plug or muff.
To explain......say a shooter uses a plug that is NRR of 27 and a muff of NRR30. The actual NRR protection would be the 30NRR plus 5 NRR for a total protection of 35NRR.
He said that the carrier flight deck crews have specially designed helmets with insulation and foam to protect the mastoid bone, have built in high NRR muffs of 33NRR and they are required to use a properly inserted foam plug of at least a 30 NRR rating.
He does a lot of long range shooting and he himself uses a low profile type of muff made by Peltor that is made wide to cover the mastoid bone, and he uses Howard Leight foam plugs that have a NRR33 rating.
He said a good rule of thumb on proper insertion of the plugs is to roll them to a small size, pull the top of your ear up with one hand and insert the plug gently till you just feel it come against you tympanic membrane. Then hold them in while they expand fully so they don't push out.
He said a good test to see if they are inserted correctly is to snap your fingers just outside your ears and you should just be able to hear it if the are inserted correctly.
He also did research on the electronic "clipping" type of protection and explained that his research proved that even if you get the fastest acting available that for that "millisecond" or so to activate... your ear gets the full blast.....but your brain never hears it but damage to the inner ear may still be occurring.
He said that his research and findings really upset all the custom plug companies and the expensive electronic companies.
I have religiously followed his advice. I have to have my ears thoroughly examined and tested every year and I can happily say that in the last 10 years, with all the shooting I do, my hearing has not declined nor has my tinnitus got any louder.