I can't speak for states outside Ohio. In Oh there are no laws saying you can't.
My question isn't necessarily if it would be practical, just legal.
I will now go on a rant fueled by much to much coffee.
My P226 with the Trident9 on it is about as long as my forearm. Not concealable at all. I have seen some of those micro 9mm cans like the Nano. They add enough length that a Glock 26 becomes longer than a 17 Long slide.
HOWEVER one must remember that sometimes a defensive shooting can land the shooter in court, be that criminal or civil. With that in mind, remember that 99.5% of the population still think that silencers are only for assassins. Your muzzle mounted hearing protection could
land you in hot water.
The "can I use my NFA weapon for defense" question has come up a million times before this. It has been beaten to death on the internets.
PLEASE don't drag the "castle doctrine" in to this. It is not a iron clad guarantee that you can shoot someone and get away with it.
PLEASE don't pull out that tired old "judged by twelve carried by six" line. You may have a conversation that goes something like
(prosecutor)"Why did you have a suppressor mounted on your pistol?"
(you)"I wanted to protect my hearing."
(prosecutor)"So, you are telling the ladies and gentlemen of the jury that when you left your house that morning, you so fully expected that you would be shooting someone that day, you brought along hearing protection? You brought along with your loaded handgun a device designed to muffle and conceal the report of a gunshot. The prosecution rests, Your Honor."
Now don't get me wrong, if someone were to kick in my back door right now they would be met by my suppressed 9mm. That said, I won't be carrying it as my primary defensive arm when I go out into the world.