It is the same problem. And chances are that the noise is still there when at idle but you really cant hear it until a fluctuation in the alternator frequency occurs. The nosie that you are hearing is what we refer to as engine noise. Your alternator puts out alternating current AC (hence the name). The whining noise that you hear is an interference by electromagnetic waves that find their way into signal wires (RCA, speaker wires, etc...) A bad ground is usually the first and easiest thing to look at. make sure that your ground wire connection is touching bare metal... use sanpaper to clear off all paint. If the problem still occurs, where are your power wires in refrence to your signal wires? If power wires are too close to signal wires, they may introduce unwanted noise into the system. There are a few other possibilities but these are the most common