Which phenomenon occurs when sound waves reflect off a surface?

When sound waves reflect off a surface, the phenomenon that occurs is known as an echo. An echo is created when sound waves travel away from the source, hit a surface such as a wall or a mountain, and return back to the listener after reflection. This reflection allows the listener to hear the same sound again after a short period of time, provided the conditions for reflection are suitable, such as a considerable distance between the source and the reflecting surface.

The other concepts can sometimes be confused with echo, but they refer to different aspects of wave behavior. Refraction involves the bending of waves as they pass from one medium to another with different densities. Diffraction refers to the bending and spreading of waves around obstacles and openings. Interference relates to the phenomenon that occurs when two or more waves overlap, which can create areas of constructive or destructive interference. Each of these processes plays a distinct role in wave physics, but when discussing the reflection of sound specifically, echo is the correct term.