I had this common problem as well. The headset jack for me is on the right hand side of the laptop at the front. Next to the headset port are 2 USB ports where I had my external mouse plugged into. By chance, while wearing my headset, I unplugged the external mouse and the buzzing disappeared. Luckily I have a USB port on the left hand side as well where I can plug the mouse into with no noise. For me it was an external peripheral. Check that first.