I was driving down the road with a friend of mine, went to hit the rear defroster button and I hear a pop sound from the speakers, once it goes away (only for a 1/2 a second) i hear much less alternator whine from the speakers. Its a new system I just put in this weekend, amp, all new speakers and double din conversion. I checked all my accessories, including the defroster and everything works. Can anyone explain this?

 

A load on the alternator reduces the interference.