Answer:
Vibrate
Step-by-step explanation:
The wave is a type of disturbance by which energy can be propagated throughout the medium. Due to the vibration in the medium particles a sound wave is produced.
It is required to vibrate the medium particles in order to create any disturbance in the medium. As a result, the medium particles transfer energy to the particles of air and hence the vibration gets transferred to the receiver's end.
So, a sound wave is produced when a medium begins to vibrate.