2004 BMW X5 audio wiring

2 weeks ago, the two speakers on the front dash started to give off a lot static. At first it was erratic, and only when accelerating on a bumpy road. I tried to switch off the radio, but it had no effect, the static continued. The static has gotten much worse, and can now be heard even when car is stationary when there is any vibration (ie even a front door being slammed shut). There is a 3rd party clarion dvd changer in the back as well, but i've tried switching that off, and still the static continues. What could be the source of this feedback?