"The angle of incidence is equal to the angle of reflection" is one way of stating the law of reflection for light in a plane mirror. Sound obeys the same law of reflection .

When sound waves from a point source strike a plane wall, they produce reflected circular wavefronts as if there were an "image" of the sound source at the same distance on the other side of the wall. If something obstructs the direct sound from the source from reaching your ear, then it may sound as if the entire sound is coming from the position of the "image" behind the wall. This kind of sound imaging follows the same law of reflection as your image in a plane mirror.

Any concave surface will tend to focus the sound waves which reflect from it. This is generally undesirable in auditorium acoustics because it produces a "hot spot" and takes sound energy away from surrounding areas. Even dispersion of sound is desirable in auditorium design, and a surface which spreads sound is preferable to one which focuses it.