5.1 Didjeridu activities  (Page 4/4)

Using didjeridus to explore acoustics

Objectives and assessment

• Objectives - In small groups, the students will use a variety of didjeridus to explore the basic acoustics of wind instruments. They will note the length, diameter, and material of each instrument, predict the effects of these facts on the instruments' sound, test the accuracy of their predictions, and make appropriate conclusions.
• Evaluation - Grade experiment write-ups according to your usual rubric.
• Adaptations - If students cannot work well in small independent groups, you can do the experiment as a class. Grade the students on participation, or have them write their conclusions.

Materials and preparation

• If you have not already done so, you must introduce the students to some basic acoustics concepts, such as frequency, wavelength, amplitude, and timbre, before doing this activity. You will find some suggestions for doing so in: Talking About Sound and Music , Standing Waves and Wind Instruments , and Sound and Music Activities .
• To do this activity successfully, you will need to have several didjeridus that play well. Instruments that are a variety of lengths, diameters, and/or materials will give the most interesting results. Each group should have at least two, and preferably three or four, instruments to test. These can be made by you or the students, as described above, or bought, borrowed, or brought in by a classroom guest.
• You will need at least one person who can play the instruments successfully. This can be you, or a classroom guest, but the activity is most effective and enjoyable for the students if the students get to play the instruments.

Procedure

1. Have them work in small groups of 2-4 students.
2. Their first step is to be able to keep track of the instruments. Decide on a name or label for each: Is this instrument #1, didjeridu A, John's instrument, the red one? If it will be difficult to tell the instruments apart, they may want to make labels using masking tape.
3. Have the students measure and record the length of each instrument, its material composition, and inner and outer diameter at each end.
4. Before playing the instruments, have the students predict what they think the differences in the instruments' sound will be, based on what they know about acoustics. Will one sound higher or lower than another? Louder or softer? Similar or dissimilar timbres? Why? Have them defend their predictions using appropriate acoustic and musical terms.
5. Ideally, for the experiment, one person should play all the instruments, so that differences do not come from different playing styles. Play the instruments yourself, or suggest to the student playing them that they should try to play each one in the same way, so that all the differences come from the instrument and not the player. If the students are all eager to play the instruments, they can each play all the instruments and note the differences in sound that come from their different playing styles. If many students will be playing the same instrument, you may want to try to sanitize mouthpieces in between players, for example by wiping with a cloth dipped in a very weak bleach solution (a drop of bleach in a bucket of water).
6. Play each instrument several times, comparing groups of two. For each pair of instruments, the group should reach a consensus comparing the instruments' pitch, loudness, and timbre and writing down the results. If feasible, you may want to try to determine the actual pitch of each instrument (for example, by comparing it with a known note on a piano or tuba).
7. Have the students compare the actual results with their predictions and write up their conclusions. If the results are inconclusive or surprising (perhaps the instruments were too similar or too dissimilar to draw useful conclusions), ask the students how they would change the experiment to check or improve the accuracy of their results.