[thedoc (OP)]

My question of the week is about the acoustics of the didgeridoo.  Could you please explain the science behind the cubic capacity of the internal chamber of the didgeridoo, in relation to it's length?  Also, if they are tuned to a western key, are they louder than an off-key didgeridoo?
Asked by Nick Lacey, Garuda, Australia

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[thedoc (OP)]

Neville Fletcher, Australia National University:
[img float=right]http://www.thenakedscientists.com/forum/copies/RTEmagicC_Didgeridoo-grass_01.jpg.jpg[/img]Over the past few years we’ve been doing a nice research project on the didgeridoo.  It’s the trunk of a small tree that’s been hollowed out by termites, cleaned out, and somewhere between 1 and 1.5m long typically.  It can either be pretty much cylindrical or flaring a bit depending on the sort of tree it’s come from.  It’s played by blowing it very much as you would blow a trumpet or a trombone by vibrating your lips.  The longer the didgeridoo the lower the note it will make.  If it’s about 1.5m long it makes a drone which is about 2 octaves below middle C.  That’s about 65 vibrations per second, if it’s cylindrical.  If it’s conical so that it flares out at the far end then it plays a higher note.  And if it’s shorter it also plays a higher not rather like the fact that a trumpet plays a much higher note than a trombone, for instance.
The main thing about a didgeridoo is that you can change the actual sound quality and doing that the player changes the shape of his mouth by moving his tongue: very much as you would if you’re saying vowels. If you go, “aaaeeeiiiuuu.” In addition people have developed a technique called circular breathing where you fill up your cheeks with air to keep the drone going and then you quickly snatch a breath through your nose. You can keep the sound going for minutes and minutes at a time.

[RD]

Physics will be similar to organ pipes ...
http://en.wikipedia.org/wiki/Organ_pipe

The sound is a rather monotonous drone,
You'll get more notes from a Didjeribone ...
http://www.didjeribone.net/
(McGonagall eat your heart out [])

[DoctorBeaver]

McGonagall? Why bring the worst poet the British Isles has ever produced into it?

[RD]

McGonagall? Why bring the worst poet the British Isles has ever produced into it?

William would be envious of my rhyming couplet (above).

[DoctorBeaver]

I doubt it because your couplet actually rhymes. McGonagall was unaware of that concept.

[RD]

Returning to the original topic...

I cannot believe the digeridoo was specifically designed to be a musical instrument: the sounds it can produce are very limited.
The traditional mouthpiece for a digeridoo is made of bee's wax, this suggests that the device was originally a water container,
the ends of the tube sealed with wax.

So playing the digeridoo is analogous to playing the bottle, not a versatile instrument, unless you have a lot of them...
 http://www.oddmusic.com/gallery/om06300.html

[DoctorBeaver]

I heard it said by a well-informed person that an aboriginal is never more than 20 minutes from water. In other words, wherever the aboriginal is, he can find water within 20 minutes. If that is true then it would seem to negate the need for a water vessel. Aboriginals wander far & wide, and water is heavy. In that heat, you would want to carry as little weight as possible. And have you ever felt the weight of a didjeridu?

In any case, kangaroo pouches would seem to be a better option for carrying liquid than a didj.

Maybe 1 of our Aussie members could look into his country's cultural (don't laugh!) heritage for us.

[DoctorBeaver]

In any case, kangaroo pouches would seem to be a better option for carrying liquid than a didj.

Wouldn't the water spill out when the kangaroo hopped ? []

You silly person, you. Sedate the bloody thing first!

[RD]

In any case, kangaroo pouches would seem to be a better option for carrying liquid than a didj.

Wouldn't the water spill out when the kangaroo hopped ? [] 

Water-holding Frog (Cylorana platycephala), from central Australia.
The frogs burrow under ground during dry periods, and emerge during the rain to absorb large amounts of water,
This allows it to avoid desiccation during drought, a trait not exhibited by most frogs.
They were used by Indigenous Australians during times of drought as a source of water.

http://en.wikipedia.org/wiki/Tiddalik

I'd have to be a lot more than 20 minutes from fresh water before I'd drink frog juice, (or Foster's Lager  [] ).

[lyner]

The point of the beeswax is to improve the embouchure. It is tailored to suit the player's lips so that they vibrate 'just right' whilst losing as little breath as possible. This make circular breathing much easier and stops you falling over after a few minutes of playing.

[RD]

In the same way stringed musical instruments originated from the bow* (of "bow and arrow"),
I suspect that the didgeridoo also originated from a more practical device, like a water container.

The wax would provide a seal for water and for air (breath), but I suspect that the water seal came first.

* http://en.wikipedia.org/wiki/Berimbau

[DoctorBeaver]

RD - it's an interesting theory, but for reasons I gave earlier I don't believe it to be the case. In addition, there are much better natural vessels for carring water available in Australia & I don't see using a didj as being preferable or even particularly practical.

I do, though, appreciate that some musical instruments have developed from items that were originally used for a different purpose, and I can maybe see where the didj came from.

Australian Aboriginals migrated to Australia. Some tribes in Borneo & Papua New Guinea have been known to use blowpipes for hunting & warfare. I can see a logical development from blowing into a pipe to propel a missile of some sort, hearing a sound & liking it, and trying to get similar sounds from similar pipe-like objects. If the Borneo, PNG tribes and Australian Aboriginals came from the same area (they do look similar, but anthropology & ancient migrations are not my forte) then there could be a connection.

[RD]

The large diameter of the didgeridoo would make it a very poor blowpipe.

However playing the didgeridoo could strengthen the muscles required to use a blowpipe…

A 2005 study in the British Medical Journal found that learning and practicing the didgeridoo helped reduce snoring and sleep apnea,
as well as daytime sleepiness.
This appears to work by strengthening muscles in the upper airway, thus reducing their tendency to collapse during sleep

http://www.bmj.com/cgi/content/abstract/bmj.38705.470590.55v1

[So didgeridoos should soon be available on the NHS []]

Indigenous Australians do wet the inside of their didgeridoo before playing it. This is circumstantial evidence for my water container theory: in a desert would you use precious water on a musical instrument ? (it was already wet inside from being a water container).

Do not pour water down your didgeridoo (an Aboriginal may do this in Australia before playing but the humidity is vastly different to that experienced in the UK and of course there are plenty of other didgeridoos growing around).

http://www.aboriginalarts.co.uk/care.htm

["wet the didgeridoo" should be a euphemism, e.g. "I’ve drank too many tinnies, where’s the dunnie ?, I’ve gotta wet the didgeridoo".  []]

[DoctorBeaver]

I wasn't saying the didj would make a good blowpipe. When using a conventional blowpipe, the user may have gotten an interesting, flute-like noise from it & wondered if other, similarly-shaped items could also produce that sound. He may have noticed that a larger capacity pipe made a deeper, more resonant sound. Keep going & you end up with a didj, or something akin to it.

I’ve gotta wet the didgeridoo

Sounds a bit rude!  [:I]

Hey, here's another theory for you... didjes were portable urinals!  []