Physics of the Vuvuzela

BzzzzzzBzzzzzzBzzzzz…

Watching the World Cup usually has great auditory accompaniment. Rousing choruses of song and cheer. The “Ooohs” and “Aaahs” of the crowd when a shot is taken.

But this year, all we hear is the Vuvuzela; that annoying plastic trumpet that no one in the crowd seems to get tired of blowing. Yet everyone watching at home is getting tired of listening.

But why are they so loud, and why are they SO annoying?

The Vuvuzela has been popular at South African sports games for quite awhile, not just at the World Cup. It was for this reason that FIFA decided not to ban the vuvuzela in the first place (despite numerous requests from players and fans).

The traditional Vuvuzela is about 60 cm long, and is played by buzzing the lips like when playing a trumpet. This produces a sound around 230 Hz (in the key of B-flat, for the musically inclined). However, the shape and length of the Vuvuzela also causes it to generate harmonic frequencies. These are sounds with frequencies which are multiples of the base frequency. In the case of the Vuvuzela, the base frequency is 230 Hz (also called the first harmonic frequency),  will produce what is called the “second harmonic frequency” at 460 Hz. The “third harmonic frequency” is generated at 920 Hz, and so on. So instead of hearing a dull hum, we get an extra excrutiating sampling of higher frequencies.

But its so loud! The Vuvuzela can actually produce sounds of up to 128 decibels, bordering on the threshold of pain. For comparison, this is roughly the sound level of a jet engine around 100 m away. Imagine that noise level sustained for 2 hours while sitting in the grandstands. Not my idea of fun.

It is so annoying too. The flared at the end of the trumpet is problematic as it accentuates the higher harmonic frequencies, which human ears are more sensitive too. This is why it sounds less like a dull hum on the TV, and more like a huge swarm of bumblebees.

There are quite a few sites out there now offering “Vuvuzela Filters” which claim to get rid of that annoying hum once and for all. But don’t get your hopes up…

Noise cancelling technology works by generating a tone at the same frequency as the one it is trying to get rid of, only 180 degrees out of phase. This causes destructive interference, and essentially eliminates both sound waves, and results in wonderful quiet.

A filter may be able to help with a single vuvuzlea blowing constantly, but a crowd full of fans blowing the horn at different times and slightly different frequencies will be extremely difficult to filter out.

Some advanced filtering software may be able to do the job, but I am HIGHLY skeptical that there is any filter that would do a good job with this situation. My advice? Get used to it. I know it sucks, but the World Cup is still exciting, and the next one is only four years away…

July 5 2010 UPDATE!

I’ve just written a post about a good use of the Vuvuzela. Check it out here!