I hear this too, but I have assumed it is some sort of "audio feedback" from the Finder to let you know what you just did. You could certainly get the same effect in OS9 but it was configurable.
I've not looked to see if you can switch it off in X.2.2, I've just got used to it. I suggest you do the same.
The noise sounds like crumpling paper to me. Figured it was just a special 'Empty Trash' sound. It's probably throwing you because X doesn't have many different sounds for events without installing a third-party app.