AUDITION, also known as auditory sensation, is the principle of the division of sensations of hearing, according to which two great groups are formed. The first is that of sensations of tone, which are musical and smooth; the second that of sensations of noise, which are abrupt, harsh and rough. The physical stimulus of audition is the vibration of some material body; this vibration is normally transmitted to the ear by a wave-movement of the air particles.