I think a lot of children can do this. I remember in middle school the entire class complaining that the TV was on, with a blank screen, and the teacher having no idea how we knew.
I can still tell when my printer has been left on, though I haven't been a child for a long time. It's actually quite an irritating sound, hence why I leave my printer off most of the time :-P
It has to do with how hearing degrades as a person ages. Some places use this to their advantage and install devices that emit high pitches so as to stop teenagers from loitering there. I know the Ikea in Brooklyn has it, for example.
