well for starters, a lot more info is needed on the car and its audio system.
if it is a simple audio system, which means that there is no factory or aftermarket amps other than the one that is built into the AVIC and you are having this problem, then you have a internal problem/ defective unit than needs to be repaired.
if you have a factory amp, there could be a few things that are causing this problem, grounding is one of them (for best results the AVIC and the amp should share a ground point) if grounding the amp does fix this then you have a very similar problem to the issue above and you can either have it repaired or just do the band aid fix as showned. you should also be able to use a GLI (ground loop isolator) if this made it worse, then you probably have a defective GLI. GLI's them selves are another type of band aid, they might completely mask the problem or they might only help.
there are too many thing that could cause ground loop interference or alternator whine, so if you dont have a lot of experience trouble shooting and fixing this problem (asking about it here, leads me to believe that you dont)you might want to =take it to a professional and have it looked at.