Public Address System (PA system) is an electronic sound amplification and distribution system with a microphone, amplifier and loudspeakers, used to allow a person to address a large public, for example for announcements of movements at large and noisy air and rail terminals. The simplest PA system consist of a microphone, an amplifier, and one or more loudspeakers is shown in fig 1. A sound source such as compact disc player or radio may be connected to a PA system so that music can be played through the system.
The process begins with a sound source (such as a human voice), which creates waves of sound (acoustical energy). These waves are detected by a microphone, which converts them to electrical energy. This signal is amplified in an amplifier up to a required level. The loudspeaker converts the electrical signal back into sound waves, which are heard by human ears