This really wouldn't work, I'm afraid. The reason noise-canceling headphones can work is that they can place microphones a known distance from each ear and in a position where they can assume they'll hear the noise before you do (i.e. immediately outward from the ear). If you're using one microphone located, say, in your lap on the N8x0, then if a sound comes from the left or right, the mic will pick it up before one ear, but after the other. There's no way it can cancel a noise after you've heard it, so it would only help one ear, and that's only if it could accurately guess how far away it is from you. Move the device and the cancellation stops working.