How does gaming headset with noise cancellation work?

I saw this new Fatal1ty Professional Series Gaming Headset Mk II (http://us.creative.com/products/product.asp?category=437&subcategory=442&product=18703&listby=) at E3 recently and was shock to discover that even though it does noise cancellation when used with the Sound Blaster X-Fi sound cards. How exactly does that work? From what I know, noise cancellation are done mostly on the headset itself. Anyone has any ideas?

The way noise cancellation is done within the headsets is by playing back a sound that bypasses outside interference so you do not hear it. That is done with hardware inside the headset, so I assume that the way the Fatal1ty works is by simply transferring the hardware process into the sound card. I'd also guess that when it comes out it will have dedicated software drivers and the like written to allow the X-Fi to work, making it no different from any other proprietary computer peripheral; or maybe the X-Fi has dedicated chipset instructions specifically for these headphones.