Sound

Any vibration in the air or other medium, some types of which are able to cause a sensation of hearing.

The vibration of any body in air or other medium causes the propagation of a sound wave. For the characteristics of such a wave, see absorption, beats, diffraction, interference, Law of Superposition, particle velocity, period, reflection, refraction, sound propagation, speed of sound, standing waves, wavelength.

The basic analytical parameters of sound are frequency, amplitude (related to sound pressure and intensity), envelope, spectrum, and duration. See also: Volume.

Sound may be defined and studied in terms of its behaviour as a wave in an elastic medium, independent of whether it is heard or not (acoustics), or in terms of its behaviour as a sensory stimulus in the ear, including the way in which the brain interprets it (psychoacoustics); or in terms of the mental processes which extract sound features for purposes of memory storage, intelligibility and problem solving (for which the term sonology has been proposed).

Compare: Audio, Electroacoustic, signal, Noise, Sonics.

The relationships between humans and the environment as created by sound constitute the field of soundscape studies, which includes the related concepts soundscape design, and acoustic or soundscape ecology. See also: sound pollution.

The absence of sound, whether relative or absolute, is silence.