I need to see a DXDIAG output. If your computer has more than one registered sound device, that can cause the problem. If the sound device is an onboard chip and you have the hardware acceleration at full (look in DXDIAG under Sound tab), then that can cause it as well.
If there are other applications trying to use the sound card/chip while the game is running, than can cause it as well.
None of this is specific to the game. It is just the way Windows is.