Half of the time I start cortex command, the sound is messed up, and when the startup sound works well, it messes up in-game, and it just does it every minimal framerate loss, not slowdown, but static. The sounds works fine when I open the raw files, instead of in the game.
Here's an example, recorded in audio output:

I've already tried reinstall and mod cleanup with no results. Any way to fix? The problem started yesterday, no modifications on the system or in cortex command other that defrag, but it was there before the defrag.
And my sound driver is Realtek HD Audio. No info about the chipset model.

Bump:
Problem had solved itself, but now it is back, and it doesn't work even without mods. Any help?