Explanation
When two identical waves move in opposite directions, they give rise to stationary waves.
Beats:
Beats occur when two waves with slightly different frequencies interfere, producing a fluctuating amplitude that can be heard as a pulsating sound.
Constructive interference:
This happens when two waves with the same phase overlap, leading to an increased amplitude.
Destructive interference:
This happens when two waves with opposite phases overlap, leading to a decreased or zero amplitude.