Echo and reverberations. Animation of a person's shout echoing and reverberating. An echo occurs when sound waves are reflected by one or more objects. If the object is a plane wall, the echo sounds more or less as the original sound. If, however, the reflector consists of many different irregular shaped objects (such as the trees in a wood), the reflected sound is a superposition of many sound waves with different amplitudes and time shifts. In this simulation, the origin wave is a person's shout, and the reflector is a wood with trees. The reflected wave front has its origin in the first row of trees and is quite sharp. The weaker reflections from trees behind form the reverberation sound.