mack/misophist -

Tuning an FM radio to an empty channel doesn't seem to produce much noise, at least with my radio in my area, and there's no such thing as an empty channel on the AM band, because there are so many little punk stations that bleed all over each other that you've always got "voices" in it.

My TV, however, produces a really great bit of static - pseudo white noise - when the local station goes off the air.

Of course, if one has cable they'd likely have to unhook the feed to find a blank spot.

John