What happens if you change headphones?? What happens if you go back to ME2 for a bit?? What happens if you change over to speaker output??
In game what sound settings have you tried?? Triple check to make sure Nvidia sound hasn't been ticked anywhere, and also make sure your video graphics hardware is defaulting to the Nvidia hardware and Intel GPU isn't being used. Yeah, Yeah, I know it is a sound issue, but I have seen weird instances where sound and graphics mixed to cause odd things...one of which is static as things go funky....