Question

what causes a disturbance that results in a wave?

Explanation:

A wave is a disturbance that travels through a medium. The cause of this disturbance is a source of energy. For example, in water waves, the energy source could be wind blowing over the water surface or a stone being dropped into the water. In sound waves, it is the vibration of an object (like a guitar string or a person's vocal cords) that provides the energy to create the disturbance.

Answer:

A source of energy.