Wave Propagation
• In solids, sound waves can propagate in four
principle modes that are based on the way the
particles oscillate.
• Sound can propagate as longitudinal waves,
shear waves, surface waves, and in thin
materials as plate waves.
• Longitudinal and shear waves are the two
modes of propagation most widely used in
ultrasonic testing.
• The particle movement responsible for the
propagation of longitudinal and shear waves is
illustrated below.