Hey!
Yes, actually this is possible...sort of. First, the covering sound needs to be caused/detected by a scripted event, like scripted artillery. I could do up a script that very briefly causes a unit to be "setcaptive true" if the unit happens to fire when arty impacts but this is only partially realistic. The problem is that if you wanted it very realistic you have to take into account the velocity of sound, the shooters position, the enemy's position, and the position of the covering sound
Sooooo say a sniper fires from 1000m. At sea level, sound travels at around 350 meters a second and will reach the enemy in a little under three seconds. if arty is going off 500 meters away, it will reach the taqrget much sooner. If the sniper fires right when the arty hits, the sound of the arty will reach the target sooner, and the enemy might hear it. If there is a barrage going on, then it would be easier to deal with, so maybe that is the way to go. anywho I'll work on it since it is an interesting challenge.
-Grendel