Auditory Illusion

I've always wondered if there was an auditory equivalent to optical illusions. BoingBoing had a clip today of a very interesting example. As soon as the clip stops, hit play to repeat it; do this a couple of times. Keep in mind that you're actually hearing the same sound segment repeatedly- it does not shift higher even though it sounds that way. Weird.

There's an explanation that I don't really understand at the original post.
Followup: There's a better explanation at Wikipedia.