The second method *apparently* involves noise cancellation. Found at antivuvuzelafilter.com, the idea is that you download an mp3 that directly counters the frequencies produced by the sound of the vuvuzela. You play it alongside the TV and the vuvuzela sound disappears. The makers explain it this way:
Our specially designed Vuvuzela noise-cancellation sound is a wave with the same amplitude but with an inverted phase to the original sound.The waves combines to form a new wave, in a process called interference, which effectively cancel each other out - an effect which is called phase cancellation.Depending on the circumstances the resulting soundwave may be so faint as to be inaudible to human ears.