The vocal-auditory channel describes the way vocal signals can be used to produce language. The speaker uses a vocal tract (containing most of the speech organs) to produce speech sounds, and the hearer employs an auditory apparatus (the sense of hearing) to receive and process the speech sounds. This is why human language is said to be based on speech sounds produced by the articulatory system and received through the auditory system. The vocal channel is a particularly excellent means through which speech sounds can be accompanied or substituted by gestures, facial expressions, body movement, and way of dressing.