The general perceptual behavior and the specific responses that are made in relation to sound stimuli. The auditory system consists of the ear and the auditory nervous system. The ear comprises outer, middle, and inner ear. The outer ear, visible on the surface of the body, directs sounds to the middle ear, which converts sounds into vibrations of the fluid that fills the inner ear. The inner ear contains the vestibular and the auditory sensory organs. The vestibular organ's function is the key to balance: this organ converts movements of the head into nerve signals.