I recently joined the ranks of those who wear the "electronic muffs". I had previously used flexible ear plugs combined with a regular set of muffs. While that worked well, I couldn't hear range commands or conversation. These electronic ones are really nifty and they work quite well, and they can actually assist you in hearing game movements nearby, while cutting out any loud (+85dB) noises (gunshots).
As far as the muzzleloaders sounding not quite so harsh as the centerfire cartridges going off... I believe it has mostly to do with the frequency range of the noise, the burn rate of the propellant, and the barrel length. I can't explain it further, but this is what a chemical engineer had told me (he also is an avid target shooter).
Unfortunately many of the older shooters probably did not use ANY hearing protection in their younger days with their .22 rifles. A .22 is really bad as the damage effect adds up slowly and sort of takes you by surprise in later years. Wear that safety/protective equipment. Our hearing will deteriorate enough on it's own as we age, don't make the problem worse!
Shoot Safely!
WV_Hillbilly