When I was a kid, we had a monitor that whined when there wasn't any video going to it. My parents couldn't hear it, but I could hear it from across the house. I'd get up when my father went to bed to turn it off.

Closer to what I think you're describing: The TV didn't "whine" really (at least, I was never completely conscious of it), but I always knew when it was on.

My hearing isn't quite as good now, but there are still a few devices that I keep unplugged because they're loud and high-pitched.