3B Scientific Experiment: Sound Propagation in Solids Features

Objective: Determine the speeds of sound propagated by longitudinal and transverse waves in solids

Thematic focus:

•    To determine the speed of sound for longitudinal waves in polyacrylic from the propagation time of a 1-MHz ultrasound signal.
•    To measure the transmission of longitudinal and transverse sound waves in solids through an inclined, planeparallel plate.
•    To determine the speed of sound for longitudinal and transverse waves from the critical angle of total reflection.
•    To determine the elastic modulus E, the shear modulus G and Poisson’s ratio of a solid µ from the two speeds.

Experiment description:

In solids, sound is propagated in the form of longitudinal and transverse waves. However, there is a considerable difference in the speed of the two types of sound waves, since longitudinal sound waves are determined by the elastic modulus of the solid, whereas transverse sound waves are dependent on the shear modulus of the solid.
By measuring the speed of the two wave types, it is possible to determine the elastic constant of the solid.