A power amplifier is a signal-processing component whose function is to increase the power of an audio signal. It will take the small signal from the mixing console & turn it into a large signal that will drive the speakers to high volume levels.
In sound systems, the power amplifier is
always the final active component in the signal chain, located just before the loudspeakers.
Sound is a disturbance of the atmosphere that human beings can sense with their hearing systems. Such disturbances are produced by practically everything that moves, especially if it moves quickly or in a rapid and repetitive manner. The movement could be initiated by: Hammering (rods), plucking (string), Bowing (strings), Forced air flow (vibration of air column – Organ, voice). Vibrations from any of these sources cause a series of pressure fluctuations of the medium surrounding the object to travel outwards through the air from the source.