Are there any published penalties for using perception from say, the room over from the one full of the guys I want to shoot (through the walls)?

Im trying to make a character based on the Sorter from Revolver and it was one of his big tricks. Right now I've got a toon with 8 Edge, 5 Intuition, 6 In perception and enough sensorware to notice nearly anything (14 Dice Pool).

I cant seem to find the penalties for say, hearing somebody walking down the hallway outside the room or on the floor above us or what have you.

You will want to get a internal (or carried) radar sensor for looking through walls.

Or you could have a microdrone inside spotting for you (with indirect fire - tacnet rules)

Other than that, i guess, the gm can deny you any direct knowledge based upon visual perception.

MAYBE you can just "hear" through thin walls, or measure vibrations. Appropriate penalties are in the perception-section of the rules (and mainly the gm just tells you IF possible... and how many dice you lose)

For example to hear muffled sounds (like behind a thin wall or something), which is far away, and you don't actively listen for it AND you are in fight. would be around -9, needed three hits at least.

Wow! That radar sensor is exactly what I needed! Now my character'll be able to pick up near anything of import. Thanks a bunch!

Yeah there's no much reson to try to wink your hearing pool or what not hight enought to hear someone behind a wall when you can actually see through walls.