Forum:Impossible spaces

I was playing the portal 2 with the developer commentary on and they mention there is 1 impossible space left in the game, has anone found this, and another intresting thing when standing on the edge of the moving room during courtasy call, i heard a faint "aaaah" when the room bumped another it was so soft andd wheatly was already taalking it couldnt be him, has anyone else heard this?