Haha, I do this too. Immediately upon entry into a room I know if the TV is on. I wonder how common this is. I don't think my hearing is any better than normal but it's like I get a vibe and I know the TV is on. This was really annoying when I hung out at my GF's house a lot, her dad would never turn the TV power off, just the "TV" button or whatever, so the red power light would remain on as well as the TV. UGGGGGGGGGGGGGGGGGGGGG! We told him like 4 times that he kept leaving it on and he never did anything about it ie: Simply TURN IT OFF! Finally he got all mad at my GF and asked her "WHY DOES THIS BOTHER YOU SO MUCH!? WHO CARES!?"

Groan. And I'm just the boyfriend so I can't say anything. Whatever.