Researchers at the Centre for Digital Music (C4DM) at Queen Mary, University of London have developed a filter that removes the droning sounds of vuvuzela playing in South Africa’s stadiums for anybody watching World Cup matches on a computer.
Dr Chris Cannam and his team at C4DM have created a “devuvuzelator”, which can be downloaded from their isophonics software and resources website. To get the filter, click here.
While some broadcasters have employed “notch filtering” techniques to eliminate the sound of the instrument, the C4DM engineers took a different approach, according to their Dan Stowell:
The vuvuzela sound energy is mostly found within narrow frequency bands – the fundamental frequency (approximately 230 Hz) and some higher overtones – so targeting those specific frequencies is a reasonable way to quieten the vuvuzela sound. Unfortunately, notch filtering also has a tendency to remove some of the energy from the commentator’s voice too, since the frequency distributions of the voice and vuvuzela overlap.
Our approach was to make a filter which estimates the amount of energy in the signal contributed by vuvuzelas, at the specific frequencies expected, and then subtracts just that energy. This ‘adaptive’ approach potentially preserves the voice energy in the signal and helps preserve voice quality.
According to a Queen Mary / C4DM press release:
The C4DM’s filter adds a degree of intelligence beyond ordinary filters. It is actually not as complex as some of the techniques developed by the group, such as source-separation algorithms which can take a recording containing a singer and a piano and work out how to extract just the singer’s voice. But the filter is simple enough that it can be run in real-time and applied to a live broadcast as it happens, on an ordinary home computer.