Something you all should know. 80% of cars and/or chargers do not have a ground isolation circuit with the accessory/cigarette port output. The noise is normal,infact it has made noise on the galaxy s 3/galaxy s2/HTC desire/HTC evo 4g/htc evo lte. The issue is caused by the ground circuit in the charger vs the signal ground via aux cable/dock. I have been a car audio installer for 9 years and have been around android since the evo 4g. This is not an android issue nor an htc issue. If you install a ps3 to a dvd on your car most likely you will get the same type of feedback especially if you have a power inverter or any high current transformer installed. Solution? Why yes ,there is a few
1. Buy a car charger with built in isolators,honestly this is hard to find since they do not advertise isolated chargers. With a good charger this may cut down or even eliminate noise and feedback
2.buy a 12v ground loop isolator and wire it behind your cigarette/accessory port. This method is my favorite because it usually eliminates ALL noise.
3.use blutooth instead of aux
12v vehicles have very unclean power,and since its direct current its almost impossible to.stop noise from high current wires so the best solution is to filter it with a ground loop isolator. I hope to help some of you with that really irritated problem.