Whenever any in game sound plays, (ambient noise, the beeping of the splash menu, guns firing, ANY sound) there is a buzzing sound in the background. Now this hasn't happened before. I just got a new computer and before I updated my audio driver through windows update and nForce driver through nVidia, the sound was fine. Now there is a buzzing sound when I play. Obviously I have tried to roll back my drivers but it still doesn't work. If this is a known problem forgive me. I would appreciate any troubleshooting help. Also if I need to be specific with my hardware let me know.
The audio is only screwed up with the latest drivers.

Try turning on A3D and EAX in audio options, and turing your display mode to D3D. I have heard this works with similar problems.

I just tried this, it doesn't work. I've tried quitting steam then opening it back up too. Nothing seems to work.

Ok I figured out my problem. I was using the latest drivers, yes, but it is obvious that Natural Selection (and only Natural Selection) doesn't like nForce drivers. For anyone else having this problems, get the nVidia unified driver.

I hope the development team is working on getting the audio fixed for the new nForce drivers.

okay, i have the same problem and....i have an ati radeon 9800 XT 256mb....yeah no nforce drivers