Hopefully it will help your case, however did you even make sure you have your sound set to stereo within you control panel? I heard a lot people that didn't have it set to stereo didn't get any sound and once they changed it, it worked for them.
Yer man ive tried everything, im running windows 7 64bit, and ive heard that directx11 doesnt work on it? And everytime i go to startup brink steam tries to install directx11, but it doesnt work. Brink works perfectly fine other then that, runs flawlessly on my ATI haha.
So im thinking it could be a problem with directx11?