A short-period oscillation of pressure such as that associated with the propagation of sound through the atmosphere; a type of longitudinal wave. Pressure waves are usually recorded on sensitive microbarographs capable of measuring pressure changes of amounts down to 10⁻⁴ mb. Typical values for the period and wavelength of pressure waves are ½ to 5 s and 100 to 1500 m, respectively. Pressure waves produced by explosions in the upper atmosphere are of value in determining the high-altitude temperatures and winds. See sound wave, compression wave, microbarm.