I was watching the World Cup last night and noticed the very noisy bee swarm noise from many vuvuzelas. It drowned out the crowd and made the commentry harder to hear.
I did some preliminary research on the vuvuzela wiki which noted the main frequencies to be 235 and 465 Hz. I downloaded a vuvuzela ogg vorbis sound file from the wiki and analysed it with Audacity, a great freeware sound editing program.
The cursor is on the 242 Hz peak and the next peak is around 465 Hz, so the figures in the wiki seem to be based on this sound file.
The vuvuzela wiki notes the following OHS effects (though the evidence was somewhat anecdotal).
- permanent noise-induced hearing loss
- a possible safety risk when spectators cannot hear evacuation announcements
- may spread colds and flu viruses on a greater scale than coughing or shouting
I then looked for more detailed data on the actual sound output and found a table in the South African Medical Journal (18 Jun, 2010) Vuvuzela sound measurements that showed the noise levels at the bell, at a person’s ear and at 1 and 2 m. I also found that Excel 2007 allows the scaling of axis at base 2, great for the geometric frequency scale we are used to, and created this graph.
Some low frequency response is there, but there is no dominant low frequency tone as suggested by the vuvuzela wiki. It is really quite flat right across the speech frequencies, and would obliterate any verbal warning message or speech. It would be difficult to design hearing protection to significantly reduce the vuvuzela’s noise to enhance speech frequencies because of the broad band nature of the vuvuzela. Active noise control with a mp3 recording is claimed in the vuvuzela wiki, but that seems somewhat fanciful as the cancelling sounding would have to be created in real time to cancel the incoming sound.
The vuvuzela appears to have deep cultural roots in South Africa which have forced FIFA to allow it, but it will be interesting to see if it is allowed at future World Cups.
