Make your own Udu

Make your own Udu

What is an Udu?

The Udu is a ceramic percussion instrument of West Africa. Although it may not be a "drum" strictly speaking, because it has no drumhead, we're not going to be picky about terminology here. You can call it a drum if you want.

Some pictures of different kinds of Udu:

All Udus have a side hole, which can be covered or uncovered by the player's hand, making a very distinctive sound which many people describe as water-like (or something like that).

Acoustic model

Almost all Udus can be modeled as a Helmholtz resonator: a volume of air (more or less spherical) with a relatively long, narrow tube connecting it to the outside air. The air volume acts like an acoustic compliance (like a spring or capacitor) and the tube acts like an acoustic mass (like a physical mass or inductor). The resonance of the compliance-mass circuit determines the low tone of the instrument.

When the hole is uncovered, it acts as a second, shorter tube to the outside. Without getting into mathematics, we can describe the result as a second acoustic mass in parallel with the first acoustic mass. In a parallel circuit like this, the smaller mass will dominate, and so (to a rough approximation) the resonance of the hole (a very short tube) with the acoustic compliance determines the high tone of the instrument.

Making your own Udu

A large plastic bottle, of the kind used in water dispensers, can be turned into a modern kind of Udu by cutting a hole in one side. The exact placement of the hole doesn't matter, just the size of the hole (and the thickness of the plastic shell). Usually, both holes of an Udu are about the same size, about 2 inches in diameter or a little less, convenient to strike or cover with the palm of a hand.

A typical bottle has the following dimensions:

Body diameter 26 cm
Body length 35 cm
Neck diameter 4.5 cm
Neck length 10 cm

Plug these numbers into the formula (with speed of sound c = 35400 cm/s) and get f = 52 Hz, which is the low tone (with the side hole closed). When the side hole is open, we will assume an effective length of the hole around 0.5 cm (most of which is fringe effect). In this case, f = 234 Hz, so that uncovering the hole should give about a two octave rise in pitch.

This page maintained by Wil Howitt
Last updated 12 May 2002