Bluetooth Speakerphone Distortion
 

Whenever I am on a call and need to turn the volume way up, at highway speeds (over 75mph), the speakers start to distort and crackle. So, I have to keep the volume at less than maximum and sometimes I can't hear the other person loud enough. Is this normal?
I have the enhanced premium audio option, so I would think it would be better. On the other hand, I have tried turning the radio music volume up to max before and have not heard any distortion.