Audio Systems: AM static, cadillac deville concours, static electicity

Question
My 1995 Cadillac DeVille Concours gets AM radio static when it moves over 5 mph.  Whether in drive, reverse, or neutral, it pops in at 6 mph and does not clear up until the car is moving at 5 mph or less.
Revving the engine in neutral and park, nothing happens, signal stays clear. What electrical device in the vehicle turns on or off at 6 mph that might cause this? This is driving me NUTS!  Please HELP!


Answer
I'm no auto audio expert but from experience I can tell you that I've had the same problem many years ago. I seem to remember that I needed a surpressor (which is a type of condenser) on possibly a battery lead. It seems to me if you go to any older auto mechanic that he will probably know what to do since it's very common. AM radio is a low enough frequency to be effected by both the engine and the spark plugs (as they give off static electicity when they fire)