A.k.a., “P.A.”; short for “public address.” A term used to refer to a sound system. Opinions from experts differ on whether this term should only be applied to sound systems used in buildings for amplifying speech (typically for making announcements throughout the building) and for background music, or whether “PA” can also be applied to a sound reinforcement system, such as a band might play through at a concert. In common usage, “PA system” and “sound reinforcement system” are used interchangeably as synonyms.

A PA system may comprise a mixer, an amplifier or amplifiers, speakers, distribution components, and various processing components, such as dynamics processors, effects, equalizers, crossovers, and more.