Hmm. I'm not sure that interference is causing this... I know that wires (or metal object) can act as an antennae but if it was to recieve transmissions from things like cell phones (unlikely as wires are very bad at being antennae), those transmissions are usually encoded or something so you would hear something other than clear distinct vioces and stuff. I mean, my mobile sometimes interferes with the car radio and you just hear beeping that lasts for a few moments and thats all, you wouldn't hear vioces even if I talked into it.