RAREFACTION

in the physics of sound, segment of one cycle of a longitudinal wave during its travel or motion, the other segment being compression. If the prong of a tuning fork vibrates in the air, for example, the layer of air adjacent to the prong undergoes compression (or condensation) upon the initial motion of the fork. When the prong springs back in the opposite direction, however, it leaves an area of reduced air pressure. This is rarefaction. A succession of rarefactions and compressions comprise the longitudinal wave motion that emanates from an acoustic source.