The concept of a plate reverb is quite simple. An electromagnet, like the one found on a audio speaker, is directly or indirectly coupled to the center of a piece of sheet of metal. Audio from a sound source is fed into this electromagnet (voice coil) which will physically vibrate the piece of sheet metal (plate). These audio vibrations are echoed many times, echos which are in fact persistence of audio. The amount of persistence (reverberation) is determined by the physical characteristics of the plate. These characteristics many include length, height, and stiffness of the piece of sheet metal. Once reverberation has been set off in the plate itself, it then needs to be detected. This is accomplish by directly or indirectly coupling microphones to the plate. The micophones pickup the reverberations and sends them back to to be mixed with the original "dry" audio.