its not a suppressor its a bug. its happened 3 or 4 times to me and a friend already. the desync is horrible after the new patches my Frames went from 90 to 120 down to 40 - 90 fps. also that random damage has been happening in stair wells, ramps, and in ditches.
Suppressors are also not meant to be completely silent and as for what i can tell in this game they are on point with the sounds they do and have made thus far. The completely silent damage is from people you cant see in the game period. They or you are not synced in the game.