I remember well when I was 8 or 9, when I was taken out in field service, I would often know from across the street whether or not someone was going to be home, because I could hear that high-pitched whine (at 15-16 kHz) emitting from the householder's television whether or not the volume is muted. I can still hear the sound when I'm near the TV, but no longer at such a distance.
Me too... no one ever believed me though. I could ride my bike down the road pointing to all of the houses that had a TV on.
I can still hear the old CRT TV's... but not as well as when I was a kid.