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Waves and Sounds

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Physics of the Didjeridu

WAVES-EIN4EI

A didjeridu is an Australian aboriginal musical instrument that consists of a long cylindrical tube. A musical tone is produced by closing off one of the open ends with the mouth and buzzing the lips to create a resonant harmonic set of standing waves.

A recording of a single long tone from a didjeridu was made. The figure below shows the spectrum of that musical note indicating the frequencies present (horizontal axis) and their relative amplitudes (vertical axis).

Spectrum of a Didjeridu. Created for Albert.io. Copyright 2016. All rights reserved.

Decide what sort of standing waves should exist in a didjeridu. Is this a pipe closed at one end or open at both ends? We can determine various characteristics of the Didjeridu based on which frequencies are present in the graph. Use the data from the figure to calculate the length of the instrument. Assume the speed of sound to be ${v}_{s} = 344 m/s$ .

A

$0.58 m$

B

$1.72 m$

C

$1.94 m$

D

$1.29 m$

E

$0.65 m$