When the sound waves reach the outer part of the ear, they travel down the external auditory canal and cause the eardrum to vibrate. The vibrations then travel through the ossicular chain of the middle ear to the inner ear. The vibrations are in turn transferred to the fluid of the cochlea, causing waves which strike thousands of sensory hair cells and their associated nerve cells. Nerve impulses so created are then sent to the brain which interprets these signals as sounds.