Many years ago a class form then Memphis State University (Now University of Memphis) came out to the range. They were studying noise levels/hearing loss. The professor asked me if I minded taking readings at my firing. I assured him I did not. (Later learned the range office directed hime to me, as I had the loudest muzzle blasts of anyone there.)
They had a device of black plastic that looked about the size and shape of a GI canteen, with an aluminum fixture where the cap would be. He took readings at my right ear (I had my muffs on) as I fired my .357 Magnum, .44 Magnum, and .45 Colt. To my surprise, there was very little difference in the decibel readings.
I have that constant ringing from my Army days when ear protection was unheard of.