stop using those headphones then report back. Direct3d is not only responsible for graphics, you can also handle audio with it. it's been a long time since I fiddled with it so I don't know for sure, but it is most probably the usb headphones as they use their own "sound card".
edit: Didn't read the edit on your previous post, please discard this comment. I am lost, I think you should seek help with the developer, but I doubt they will even listen or care.