I was at a lecture yesterday and there was a demo of a van de graff generator. He held the smaller metal globe which is attached by a wire, about 4cm from the main globe. This created a spark between the two globes. At the same time the spark happened the speakers in the hall would click loudly, the projector (on the other side of the room) would turn yellow and the text moved down, then flashed black and back to normal. And the plasma globe that was next to the van de graff generator which was switched off (but on at the wall) would briefly turn on.
Is it possible for a spark to do that? Or is there something else happening at the same time?