Sound particle

Sound particle an imaginary infinitesimal volume of a medium that shares the movement of the medium in response to the presence of sound at a specified point or in a specified region. Sound particles are not molecules in the physical or chemical sense; they do not have defined physical or chemical properties, or the temperature-dependent kinetic behaviour of ordinary molecules. Sound particles are, then, indefinitely small so that their movement truly represents the movement of the medium in their locality. They exist in the mind’s eye to enable this movement to be visualized and described quantitatively. Sound particles vibrate about fixed points. Hence sound particle displacement, sound particle velocity etc. In context, the word sound is often omitted.