what am i hearing?

when i was setting up my speakers i faded all the music to the rears, and while i was doing that, i was hearing a 'noise' of some sort coming from the fronts, it sounded like static, but it was static of the music playing, ie: if you payed attention to it, the noise was related to the music in some way. I tested this on a real cd, so i know its not the CD, which i was never figuring it was, but it rules 1 possibility out, any ideas if its just my deck (SONY MP40) still outputing sound through my fronts at a certain level. My rears are the only speakers hooked up to my amp at the moment, i'll test today wheather a sound is produced from them as well while playing music with the fader set to the fronts. i am just curious what this noise is, the static seems to clear up once i put the fader anywhere but the very rear so it really hasnt posed a problem, but for curiosity's sake, i'd like to know, or have an idea :-).

Yes, you are most likely hearing noise from your head unit.  It is called "poor quality." Support the12volt.com

hehehe which is the reason why included it being a sony ;p, its gonna be changed, im just happy it plays cd's right now, it was the first aftermarket product i put into the car, my ideas and knowledge has changed drastically since that purchase