Just tried this in l4d using sounds built into l4d and it worked, but it plays when temp health drops, or when survivors get hurt. Is there a way to make it so sounds only play for the attacker? I'm trying to get hitsounds working, and this is the closest I've come.
Nevermind, after searching for hours, I come across
http://forums.alliedmods.net/showthread.php?t=99552
20 mins after posting this.