Bluetooth "Buzzing" when my lights are on
 

Hi. I have had the most annoying problem since day one with my A3. When I place a call with Bluetooth, sometimes the person I was calling would tell me that they could barely hear me over the sound of a loud buzzing (but I never could hear it). After a long, long, time I made the realization that it only happens when my headlights are on. It has happened with every phone I've had with this car (3+ Blackberries). Any thoughts?

Christine
'07 A3, 3.2 Qtt S-Line