speakers making noise w/windshield wiper movement?

[whitesho]

Hey guys, every time I have my stereo on and the windshield wipers are going, the stereo will get like a static-like noise when the wipers move. Any idea what this is?

thanks

shoot noisy windshield wipers shoot shoot

 

[Tommy's SHO]

I have the same problem but only when I am listening to AM and going under a bridge.
I bet it has to do with the alternator.

 

[RickieFrat]

How do the speakers sound when the wipers are not on ?? Do they sound distorted at all ?? Is it all your speakers or just one ??