All in the Heartbeat

I have the stock CD player with the stock Pioneer system in my 06 SS/SC. When I turn the volume somewhat low on the stereo, I notice a light (but very annoying) static in the background. I tested all of the speakers and none of them seem to be blown. I'm not sure what else it could be. Has anyone else noticed this?

SS SCHGD

both of my stock SS/SC systems have that static in them, and when I added a LOC it made it more noticable...I've heard of other stock 7 speaker pioneer systems with it too.