We've all read the reviews on this site and on others about the Creative X-Fi and the Icemat Siberia USB device. The one major point that every one of these reviews make is to praise the 3D positioning ability of these devices using only a 2-speaker headset. How could this be possible? How can mere humans compress a seven speaker sound system into a simple headset? It involves a complicated application of audio theory and computer processing muscle.

No matter where you are in the world, no matter what kind of sound you hear, it is still only heard by two ears, not 7.1 ears. The idea of virtual surround sound (VSS) technology is based around this fact. The application of this fact is based on the idea of Head Related Transfer Functions, known as HRTFs. These are mathematical equations that explain how a sound takes it's path from a source location to your eardrums. These functions cannot be calculated independantly from an experiment. They are determined in laboratories by measuring the amount of sound at each ear drum of an anatomical dummy and comparing it to a corresponding test signal from somewhere in the sound-proof room. By knowing what the test signal originally was and how it was received on both of the dummy's ear drums, a function can be extrapolated that describes the path the sound took. Theoretically there are infinite HRTF's, one for every single point in a geometric field. The trick is to limit these HRTF's to some sort of arbitrary number.

In most modern VSS technologies, this limit is set at 7 separate points. Since the HRTF of these points is an algorithm, any sound generated at these points will go through that equation on it's way to the left and right ear drums. Now here comes the trick: Since headphones send sound almost directly to the ear drums, a VSS system simply eliminates the pesky middle man of open space. Open space would naturally apply the HRTF without any sort of calculations, as this is how we can perceive positioning through our ears. If the sound device already applies this change in sound to both of our ears, then there's no need for the open space to do it. This sound can then be fed directly to our ears by using headphones.