I recently purchased a used 04 audi a4 3.0 quattro sedan, the stereo system single din pioneer and this head unit had the alternator whine coming through the speakers, when turning the headlights on only made the electrical whine louder . So i bought a new single din stereo head unit, and I'm still hearing the same noises as well as when i drive by power lines...what the heck?!?!? I tried the youtube ideas of grounding the RCA cables to the head unit and still that did not help one bit....

 

Are you using an amp and Sub(s)? Alot of the times depending on where the wires are run Ie: running the power and rca on the same side can cause engine noise. No sure why power lines would cause you to get noise through your speakers unless there is a radio frequency being generated that is catching a signal in your car.