Center channel speaker refers to an audio channel common to many surround sound formats. It is the channel that is mostly, or entirely, dedicated to reproducing the dialogue of an audiovisual program. The speaker(s) connected to the center channel are placed in the center of and behind the perforated projection screen, to give the effect that sounds from the center channel come from the screen. In many home surround sound units, the center channel is positioned above or below the video screen.