Tool "Prison Sex" Intro

I got this info from and it is credited to

This is the weird noise heard at the beginnings of "Prison Sex" from TOOLs CD Undertow. Tune your low E string down to B, then hold down the tremolo bar so that the string is loose. If you strike it, it should sound like its just flopping there. The next thing you need to do is run your pick over the string to get that scratching sound (you should still be holding the tremolo down). Finally, hit the string one final time and slowly release the tremolo bar (if you do it right, it should sound like it is speeding up). A delay pedal may help as well.