Around WW 1 they put silencers on 1903 Springfields and set out to test the silencing ability. The range they were using had a row of power line poles parallel to the flight of the bullet. Though the gun blast was almost silent every time the bullet past a pole it would leave an audible crack from the faster than sound bullet. It went CRACK, CRACK, CRACK, CRACK, CRACK, Not to stealthy
I believe navy seals when using 9mm pistols use heavier weight, subsonic bullets so as to optimize the use of their silencers.
I can just imagine a successive crack crack crack as it goes down the pole line, LOL
For the ultimate in stealth,subsonic loads in a semi (or single shot bolt pistol (TC)) especially if the slide stays forward after firing is very quiet.
grease guns with silencers sounded like a sewing machine in the next room, only the sounds of the action itself were heard.
Would be cool to have a .22 rifle, 1000 fps with a light scope, and for heavier work, a .45 with 850fps projectiles.
9 mm's come with a variety of cans, most of them work very well.
There is a short tape on you tube regards hydraulic filters that is fun to watch.
I will see if I can find it.
The idea is to mask the sound of the muzzle blast and confuse the enemy as to direction of the shooter. You cannot tell the direction a round came from by the sound it makes passing you.