I can see three real choices here. The first is what we have now: you see practically everything, even things you shouldn't be able to or don't want to, regardless of where it is. The second is that some areas, which ones being up for debate, get completely blacked out when certain conditions are met.
The third, and I like this one, is that areas suitably out of the sight of your dwarves fall under something of a fog of war. A room nobody has been in is rendered in greyscale rather than color and its image is nolonger updated. Even if everything in the room burned down two years ago or your supply of plump helmets has changed into 20 dog-sized giant rats, you won't know if nobody has been down there. If we don't add in some sort of color change, people would have a really hard time figuring which information they can trust and which they can't.
Perhaps flashing colored icons (periods or dashes for quiet sounds, asterisks or coin symbols for loud sounds) pop up in tiles where something is making a lot of noise and there is a dwarf on the other side of a wall to hear it. I might even change the color of the icon depending on the basic type of noise: Red for crunches or pounding against rock, aqua for blades or shattering sounds, blue for water sounds, brown for scuffling or rummaging, yellow for vocalization.
I would also add an option to 'forget' what was in a given set of tiles, wiping your knowledge of what used to be there and rendering those tiles black.