I'm with pezo and Ole Coot on .22 Mag noise levels. Been shooting them since High Standard came out with its derringer in the Sixties, and have owned most non-junk brands ever made.
Most folks buy into the gun forums' "too loud" stories because they see the stories repeated all the time; so they must be true: "Hell, my Uncle Judd who shoots .44 Mags at the range almost went deaf because a guy in the next booth shot off a .22 Mag!"
Even the above-posted decibel chart shows that .38 Specials are louder, but no one at the range complains, and no one on the forums ever said "Hey, them ole .38 suckers sure are loud." Why is that?
Here's why: People confuse a loud report with a sharp report, and that supersonic .22 WMR out of a tiny little weapon like a S&W 351 is unpleasantly sharp.
That surprises people who were expecting only something like the crack of a .22 LR Stinger.
Most people think a WMR round is just a souped up .22 LR rather than a kissen cousin of a standard .38, so when they hear a WMR with no hearing protection, feel the b/c gap blast and see flame spit out of a little rimfire handgun, what's the natural reaction? It's, "Holy Shiite, that's a loud SOB!" And in a sense, they're not all wrong.
For one or two finishing or plinking shots in an open field with a .22 Mag, I don't feel the need for hearing protection, just like with a 12 gage shotgun. Of course, YMMV so by all means play it smart and wear protection if you want to.