all these is a combination of stuff. some soundcards, some 5.1 systems, some play b2 with software rendering, some hardware (its an audio setting). All is dependant on compability with EAX.
I suggest turn on, off EAX, try medium/high sound, try software/harware rendering.
but that's just to make you able to play now. ofcourse we must fix all this, and me and Kev4000 are dedicated to fix all these issues for next patch.