TECHNOLOGY FOR CHANGE

Audio Engineers Tackle the Vuvuzela

Salvatore Salamone | Date: 06-30-10 | Comments

Anyone who has watched a second of any World Cup 2010 game knows the distinctive sound of the vuvuzela. Its endless hum has dominated all TV broadcasts. And for many viewers, the sound is annoying and distracting. For those watching the games live on a computer, there is now a way to remove the sound.

The World Cup has brought us incredible matches, disputed calls, fights between players and coaches on the same team, and Academy Award-level performances on some player dives. But what most will remember long after the last goal is scored and the winner is crowned is the unique and pervasive sound of the South African horn, the vuvuzela.

Anyone who has watched a second of any World Cup 2010 game knows the distinctive sound of the vuvuzela. Its endless hum has dominated all TV broadcasts. And for many viewers, the sound is annoying and distracting.

The vuvuzela's hum has dominated World Cup TV broadcasts (source: Centre for Digital Music [C4DM] at Queen Mary, University of London).

How annoying is the hum of the vuvuzela? After just a few games, The Guardian ran an article with the tagline: "Turn down the volume, shove in the earplugs, for a raucous horn is threatening viewers' sanity during the World Cup."

For those watching the games live on a computer, there is now a way to remove the sound. Researchers at the Centre for Digital Music (C4DM) at Queen Mary, University of London have developed an algorithm that removes the vuvuzela's hum without distorting other portions of the broadcast audio.

In theory, the removal of a particular sound from an audio track should not be that difficult. But it turns out that the removal of the vuvuzela's sound posed some technical challenges.

According to the researchers, various approaches had been discussed by audio engineers. Many tried a frequently used "notch filtering" approach, which removes sound energy from specific frequencies.

The vuvuzela sound energy is mostly found within narrow frequency bands�the fundamental frequency (approximately 230Hz) and some higher overtones�so targeting those specific frequencies is a reasonable way to quiet 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.

The C4DM's filter uses a bit more intelligence to complement ordinary filters. And while complex filtering has been done in other areas where there is a meshing of frequencies (for instance, filtering out a singer's voice from a piano), the filter developed by the C4DM researchers is simple enough that it can be run in real time, on a home computer, and can be applied to a live broadcast as it happens.

"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 [subtract] just that energy," states Dan Stowell, a researcher at the C4DM. "This adaptive approach potentially preserves the voice energy in the signal and helps preserve voice quality."

For those who want to give the filter�dubbed the devuvuzelator by the group�a try, the group has made the software available through its isophonics.net Website here. This site allows you to download the software and contains instructions about how to use the application with various operating systems and different audio connections.