Yesterday I started noticing that my computer randomly makes 2 quick noises in a row that sound like sandpaper being scratched together. The first is a longer noise, the second is the same type of noise but abbreviated. It happens when I am using the computer at random times (maybe every 10 minutes) and also when I am not using the computer, just a few feet away perhaps. Any ideas? ... This noise is annoying because I have the volume on quite a bit due to medical transcribing w/ sounds files.