If a sound is not absorbed or transmitted when it strikes a surface, it will be reflected. The law for reflection is the same as that for light, i.e. the angle of incidence of a sound wave equals the angle of reflection, just as if it were produced by a 'mirror image' of the stimulus on the opposite side of the surface. However, this law of reflection holds only when the wavelength of the sound is small compared to the dimensions of the reflecting surface. Compare: diffraction.

See: Canyon Effect, Diffuse Sound Field, Sounding Board. Compare: Anechoic Chamber, Free Field.

Reflection of a sound wave at a barrier, as if from an imaginary source at an equal distance behind the barrier.

Sound reflection gives rise to diffusion, reverberation and echo. Different surfaces have different reflecting powers, as measured by their absorption coefficient or reflection coefficient. In general, concave surfaces focus sound waves, thereby concentrating the sound in specific areas, and convex shapes scatter sound, thereby promoting good diffusion.

Symmetrically-shaped surfaces produce symmetrical reflections, the most striking examples of which are the whispering gallery, where sound travels along the walls via repeated reflections, and the parabolic reflector where all sound is reflected to the focus of the parabola.

See also: Binaural Hearing, Phasing, Sound Propagation. Compare: Absorption, Acoustic Radiation, Refraction, Transmission.

Reflected sound from the opposite side of a lake, heard as an echo.

Multiple echoes produced under a parabolic bridge, Stanley Park, Vancouver, B.C. The source sound is a stick hitting a metal can.