It's a blue screen signal from a vcr going into one modified distribution amplifier, then that signal is going through another modified distribution amp. The audio heard here is coming from the video out of the second distribution amp---the same split signal as the video signals sent to the TV's. Without any volume on the TV, you can still hear the same sounds if you put your ear up to the TV tube---the sounds of the electrical beams bouncing around inside the tube and hitting the phosphors on the screen.