Do you know how to do the other version, when you attempt to sing a lower pitch than your natural voice supports?
There are various techniques for this as well, and I know of only two, of which I only master ½ :-P
Throat singing is the most used technique, a friend of mine could do one such variant: he somehow growled while singing about a fifth above his lowest note, and produced a (fake) tone an octave lower with the growl. This was incredibly loud, and didn't resemble singing as much as it did, eh, growling. He tried to explain it to me (this was years back) but I didn't quite get the hang of it. He said that somehow you make your "false vocal cords" vibrate and the resonance gives you the octaver effect.
The technique I'm starting to get the hang of is called Strobas (don't know the spelling). You sing a note (also here, it isn't that easy with your lowest notes so maybe a fifth or sixth above your lowest note) and, while singing it, start making a creaking, grating noise. Think of an old door creaking. If you do this right, you make the impression of singing an octave lower than you actually do.
You can also "sing" with a creaking voice (without a tone an octave higher) and make the impression of singing real low. With this kind of fake singing I can reach the lowest C on the piano (with my real voice only the G sharp above).