Audio Stuttering

Whenever any sound is played on my machine the audio stutters. This includes youtube videos, streaming from google music, playing music in itunes, and even when I change the volume (without any media playing). I am running Mac OS X 10.6.8. The problem went away for about a week (I'm not sure why), but then came back. I can't think of any software that I've installed that would have caused this and have no idea what the problem could be. Any help would be appreciated. Thanks!