Make sure you have the cable plugged into the right hole in your soundcard. On my old soundcard I could plug it into the wrong place and it'd still generate sound, but it sounded kind of like what yours does. Check all the other cables too. To your speakers and whatnot. Maybe try another set of speakers to make sure that it isn't just your speakers that're broken. Also, do you have a microphone plugged in? If so take it out and see if that helps. There are a lot of things to try. I can't think of any more.