This problem just started a month or two ago, but is now happening more and more frequently.
(a) It comes and goes when driving over bumps, or turning the car.
(b) It does not go away after turning off the stereo. The buzzing even continues after turning the car off and removing the key.
After Googling around some, it appears there are a lot of problems with the Monsoon system. The only info I could find was that it's a common problem, but there was never any mention of a fix.
While looking around in back of the car trying to figure this out, I never realized how staticky the rear speakers were. You really don't notice unless you're in the back with the speakers.
Anyone else here had to deal with this yet?