Hearing is the ability to perceive sounds by detecting vibrations or changes in pressure through the ear. Sounds may be heard through solid, liquid or gaseous matter. Hearing is one of the traditional five senses. If someone has the inability to hear it is called deafness. Sound is the mechanical oscillating wave of pressure transmitted through some medium. It is composed of frequencies within the range of hearing.
In vertebrates, hearing is performed by the auditory system. Vibrations of sound are detected by the ear and transduced into nerve impulses. These nerve impulses are then perceived by the brain. Similar to the sensation of touch, hearing requires sensitivity to the movement of molecules in the world outside the organism. Hearing and touch sensations are types of mechanosensation.
The human ear has three main components, the outer ear, the middle ear and the inner ear. The outer ear includes the visible part of the ear, the auditory canal and the eardrum. The middle ear consists of a small air filled chamber that is located behind the eardrum. Within this chamber are three small bones referred to collectively as the ossicles. The inner ear contains the cochlea. The cochlea is a spiral shaped fluid filled tube that is the organ of auditory transduction.