Went to a customers home to find the source of noise that affected their television and radio. The noise affected all channels and all of the fm band.The first thing we checked was connection at the outlets, found back stabbed devices, no sign of trouble there. Out came the o-scope, no noise on the ac line so we decide it has to be in the air like it was broadcasted. Next trip there we brought along a frequency counter that we used to trace the source of the signal to the attic and a doorbell transformer. The transformer would make a buzzing sound and with each buzz we would see a signal from the frequency counter. We disconnected the transformer and all is well now. I gave the customer a couple of options to properly install a new transformer not in the attic.