First, I used to work in the hearing healthcare industry in new product development with someone who worked with niosh on the new impulse noise standard that got shelved. I researched as much as I could, but honestly there was not that much research (2013-14). In the end, the best protection is electronic muffs over a solid or foam plug. Btw I wear electronic plugs for hunting and this year will be hunting suppressed subsonic with no protection. Imho the best thing is buy a suppressor. If that’s not an option, then electronic muffs.
To hear normally and then block loud impulse noise is the holy grail of hearing protection. With todays technology the best option is something electronic. Either plugs or muffs. Muffs are a lot cheaper, in ear electronic runs a lot more.
passive protection (ie not electronic) that is level dependent is marginal at best. The 3m system which they lost a huge lawsuit, worked better than all the other stuff we tested. Imho their problem was they used crappy earplugs which didn’t seal well making the whole system marginal.
the way the 3m protection works is a really small hole is used and it limits the amount of energy that can flow into the ear. Think small nozzle on a hose. looking at the test data, the max protection was about 15 db at 155 if I remember right. So at best it’s right at hearing safe. Lower noise offers less protection and more doesn’t offer more. There is a white paper out there on the design. It takes a really small hole. Around .010” if I remember right. they also whistle in the wind. Westone offers the one I designed in custom earmolds and has published test data available. Not a cheap option and for a kid who is going to need new ones every year, probably not a good option. The sonic valve style seemed to have too much inertia to work very well. Better than nothing, but not by much.
