The New Scientist asked Trevor Cox, president of the UK Institute of Acoustics and an acoustic engineer at the University of Salford, UK, to explain. (more at http://isophonics.net/content/whats-all-about-vuvuzela) Basically he said that our hearing is an early-warning system: we listen out for sudden changes in the sounds around us which might indicate threats, and ignore benign, persistent noise. When noise becomes as loud as a vuvuzela, however, it becomes impossible to habituate to the sound.
If you are watching the match on a computer, you could try a handy application, from the Centre for Digital Music at Queen Mary University of London. Here they say that the vuvuzela has been badly received by some television viewers, who have complained that this magnificent pipe, after transmission, comes across as a resonant buzz which the sensitive listener may find hard to tolerate.
The site goes into some complicated stuff about time-frequency plot and the difference between a voice and the vuvuzela. You can read about all the gubbins at the site linked above.
For Windows users who would like to remove some of the sound generated by these things, Stardock have made an application which wraps around the above plugin and automatically filters your web browser's audio output. Get it at http://www.stardock.com/labs/devuvuzelator/ .
