Voices through tv,stereo,landline phone..tvs flicker?

I cannot give you any technical details - it's way beyond me, no doubt someone out there will explain it all to you. But you are not alone in this sort of thing. 34 years ago I had a Russian choir comeing in over the baby's monitor, and a group of my friends living in the flats opposite could all hear the couple on the top floor making love over their baby monitors, through the couple's baby monitor.