Alternations of SOUND PRESSURE or particle displacement following one another in CYCLEs of COMPRESSION and RAREFACTION through a medium such as air. On striking the ear, it may be heard as SOUND.
Compare: ACOUSTIC RADIATION, OSCILLATION, SOUND INTENSITY, TRANSMISSION, VIBRATION.
Sound pressure variation of a sine wave showing the PHASE relationship between pressure and particle displacement.
Waves may be of two sorts, transverse and longitudinal. While solids will transmit both kinds, liquids and gases will transmit only longitudinal waves and the study of sound waves is thus largely concerned with this type where the AMPLITUDE variations are in the direction of propagation. Nevertheless, as transverse waves are easier to display graphically in two dimensions, sound waves are usually shown as if they were transverse waves, for instance on an OSCILLOSCOPE or in the above diagram. See CYCLE for other diagrams.
For the properties of sound waves see: ABSORPTION, ACOUSTIC IMPEDANCE, BEATS, CANCELLATION, DIFFRACTION, DOPPLER EFFECT, FREQUENCY, INTERFERENCE, LAW OF SUPERPOSITION, PARTICLE VELOCITY, PERIOD, REFLECTION, REFRACTION, SOUND PROPAGATION, SOUND SHADOW, SPEED OF SOUND, STANDING WAVES, WAVELENGTH.