The speed of sound in a solid is determined by the density and elasticity of the material. Young’s
modulus can therefore be calculated once the density and the speed of sound in the solid are
measured. The density can be measured relatively easily, and the speed of sound through a rod can be
measured very inexpensively by setting up a longitudinal standing wave and using a microphone to
record its frequency. This is a simplified version of a technique called ‘impulse excitation’. It is
a good educational technique for school pupils. This paper includes the description and the free
provision of custom software to calculate the frequency spectrum of a recorded sound so that the
resonant peaks can be readily identified. Discussion on the effect of measurement uncertainties is
included to help the more thorough experimental student improve the accuracy of his method. The
technique is sensitive enough to be able to detect changes in the elasticity modulus with a
temperature change of …