They really make a shotgun sound like a pop gun. Very quiet. One of our machinist at work built one that would screw into the choke tube threads.
One of our Game rangers that works there as security on his days off warned us that they weren't legal to use in Okla before we ever got to use it..
That was before the new hunting regulation that now allows silencers to be used in the field while hunting as long as the person has the correct federal stamp.
The muzzle blast if you want to call it that runs about 72db. Not enough to require hearing protection at all.