I checked 'em all just to make sure. Even the gauss and flame weapons the "silent" box is checked.
-Gunny out.
Interesting. I'm not sure that setting's doing what it's supposed to be doing. I've just been doing some testing of my own:
Take one stealth-boyed, NCR-garbed Courier, plant in Ranger Camp Echo. There are three rangers, two regular and one vet, at the outset they're all yellow on the compass. Courier crouches six feet from vet and shoots him in the head w/silenced sniper rifle. Result: 1 dead vet, 1 still-[hidden] Courier, two remaining rangers still yellow on compass.
Now, same scenario repeated but w/Gauss Rifle instead, and the result: 1 dead vet, two remaining rangers now red on compass, and [caution] status for Courier. Got the same results with the Multiplas too.
I suppose the stealth-boy and/or the faction armour may be affecting things somehow, I don't quite have a perfect high-sneak-and-EW character I can test this with (most suitable candidate is spoiled by having Meltdown.)