I'm an audio engineer, thanks for telling me that. You're not strictly correct though. They have to use phase inversion of the waveform (take the sound, and make the sound waves that go up, go down, and vica versa) and then use Subtrative Synthesis to remove the sound. The problem with this is that they don't want to go removing too much of the rest of the crowd noise at the same time, which both of these effects could do because for it to be effective you need the two sounds to be 180 degrees out of phase. When if you're using a recording, they're going to be more like 90 degrees out of phase which will create a "sucked out" effect, but it won't remove the sound's presence much at all. The best way to do it is create a 2 second delay on the broadcast, use those two seconds to record the audio on a two second rolling loop, use a band filter to isolate only the frequencies of the Vuvuzula playing, phase invert that section and slowly blend it back in with the original audio, thus it should be 180 degrees out of phase and you're slowly cutting out the Vuvuzela.
|