Fluctuations in air pressure due to the presence of a sound. This sound pressure is expressed in units such as Pascals, microbars, or dynes/cm2.
the difference between the instantaneous pressure at a point in a sound field and the average pressure at that point
Root-mean-square instantaneous sound pressure at a point during a given time interval. Unit, Pascal (Pa) (ANSI S1.1-1994: sound pressure; effective sound pressure).