Didgeridoos give ears a hammering
The noise inside the mouth of a didgeridoo player reaches levels almost as high as a jackhammer and could cause hearing damage if we had ears in our mouth, new research shows.
A study published in the journal Nature today is the first to look at the acoustics of the didgeridoo, the world's oldest wind instrument.
(Sound: Lloyd Hollenberg/mp3 file, 238kb)
Professor Joe Wolfe of Sydney's University of New South Wales and colleagues measured the acoustics of the didgeridoo, an instrument played by indigenous Australians traditionally made of a long wooden tube hollowed out by termites.
They measured the acoustics from within the player's mouth using a system of tubes and microphone probes.
Wolfe says the noise in the mouth reaches about 100 decibels, which is about as loud as a noisy nightclub and about 10 decibels lower than a jackhammer.
"This is very loud," he says. "Sustained 100 decibels at your ear would be dangerous."
Similar levels are present in the mouths of trumpeters or clarinet players, he says.
A unique instrument
The didgeridoo is a unique instrument as it usually only has one note. Its predominant musical feature is its huge range of timbre, or tone colour.
The didgeridoo's range of timbre is only equalled by the human voice although the organ comes close, Wolfe says.
He says changes in timbre are produced by varying the shape of the tongue and vocal tract, just like we do when we make different vowels in speech.
The lip mechanism used is similar to techniques used for playing brass instruments like the tuba and trombone.
"The mechanism is a little bit counter-intuitive," Wolfe says.
"It turns out that the resonances in your vocal tract cut off certain sounds and it's the sounds that remain that are important."
He also describes the didgeridoo as "a little bit like your voice in reverse".
In speech, the resonance originates from the vocal cords and travels out through the mouth. But in didgeridoo playing the resonances originate at the lips before travelling down the vocal cord and back out through the instrument.
Not as simple as it looks
The article's lead author, Dr Alex Tarnopolsky, says the best sound comes out if the vocal folds are nearly closed at the glottis, the opening at the upper part of the larynx.
"Otherwise the resonances aren't strong enough to stifle those frequencies," he says.
"We conclude that a major difference between a novice and an experienced player is a learned, but usually subconscious ability to reduce the glottal opening."
Wolfe says most wind musicians learn the glottal technique over several years and it appears that didgeridoo players do it intuitively.
"As with speech you're trying to imitate particular sounds and you do various things, not all of them conscious, until you get that sound," he says.