Scratchy sound

[thepepsiad]

I've had an issue with my sound for the last couple of weeks. I haven't done anything different to my computer, but whenever I listen to music or talk on Ventrilo, I can hear the music and people talking, but I also hear a very loud scratching sound. I've tried both jacks in the front and back of my tower, and also have tried alternate speakers and 2 different headsets. I have no idea why its scratching or how to fix it.