Things like:
You hear the scuffle of hand to hand combat to the East.
You hear the swish of a blade coming from the North.
The rattle of automatic gunfire comes from the East.
You hear a loud kablam from the southwest and above.
I remember in a number of events in the past, people would wholesale ignore the room descriptions of gunshots and fighting happen to chase gunshots from a few blocks down the streets. I realize that there is specific equipment that helps address this problem, but feel that the addition of combat sounds from all kinds of weapons - melee or ranged - would be of benefit to the game.
Let's add some player paranoia to the everyday experience of living in the mix.