Those waves in which the disturbance (back and forth motion) takes place in the direction of propagation. Sometimes called compression waves.
Commonly used term for compressional wave.(Basic Science/vibration/discussion002.htm)(Course Material/Ultrasonics/MeasurementTech/velocitymeasure.htm)(Course Material/Ultrasonics/Physics/wavepropagation.htm)
waves such as sound where the particles move or vibrate parallel to the direction of the wave.