It'd be nice if each weapon featured a volume rating which specified how far away (in tile radius) a weapon's gunfire could be heard. This system could also be applicable for things like opening doors, and movement. Like explosives, the sound of an action could be dampened by walls and obstacles. This makes a lot more sense than automatically being privy to the audio your opponent generates anywhere on the map, and increases the importance of proper scouting.
If we were to take this an extra step, you might also include stats like Perception and Stealth; higher Perception increases a unit's effective sight and hearing range, while a higher Stealth rating effectively reduces the range at which a unit may be seen and heard.
Edited by Emperor Clobbersaurus, 11 March 2010 - 10:45 AM.