[pepperammi]

If you've got a Creative card/chipped device it could be the somewhat notorious sound pop n crackle issue specially on X-Fi cards. Something to do with the cards buffer being starved in some system configs by the pci bus (some get it with the newer pci-e port versions too apparently) when under heavy load, or something like that, which I suppose Cryostasis could be putting systems under since runs so poorly.
Creatives only 'fixes' for this at the moment is to try disabling 'crystallizer', going into speaker properties phm mentions and check the 'Disable Sound Blaster enhancements' under the 'Sound Blaster' tab Making sure all unnecessary background apps are terminated to reduce load, oor even try un-installing all the drivers and traces than try putting the card in a different card slot and reinstalling the drivers ect.

I get the occasional game that has issues Like Crysis but disabling Crystallizer seems to work. I'm too lazy to try another pci port with my x-fi extreme gamer fatal1ty pro card