I.e. when a creature is behind a wall, I should damp or turn off the sound it makes. On the other hand, when a open door is next to the wall, I would hear the creature, even if it is not visible. To make it even more complicated, the sound would come from the direction of the door, not the wall. Even more complex: What if there are two doors, one to the left and one to the right of the player and a wall between player and creature ?
Something like this:
C -| |-------| |--- P
To be honest, I don't have the time to create an accurate sound landscape, nor will I add some audio libs which handles occlusion (EAX?). I would like to hear some feasable/common tricks of handling this kind of issue. I have a waypoint system which could be utilise to handle/fake sound reflection, but I don't know if this kind of fakes are too clumpsy.