Sound waves travel as vibrations in the air. These vibrations are detected by our ears, which send signals to the auditory centre in the temporal lobe of the cerebrum. The ears have three sections, the outer, middle and inner ears.

Outer and middle ear

The outer ear consists of the cartilaginous auricle and the external auditory canal, which is separated from the middle ear by the eardrum. The auricle gathers sound waves for the middle ear. Essentially, the eardrums act like drumheads; they pass the vibrations from the air to the tiny auditory ossicles in the middle ears (malleus, incus, and stapes, or hammer, anvil and stirrup, respectively). These little bones are in an air-filled cavity, and their function is to transmit the vibrations from the eardrum to the inner ear. The middle ear is connected to the pharynx through a thin canal, called the Eustachian tube.

Inner ear

The cochlea of the inner ear is a spiral-shaped organ in a cavity of the temporal bone of the skull. It contains an outer bony labyrinth with a similarly wound-up membranous labyrinth inside. Tiny auditory receptors (hair cells) sit in the membranous labyrinth, surrounded by a liquid. The organs of balance are connected to the cochlea, and they include the utricle, the saccule and the three semicircular canals.

Sound is vibrations in the air. Entering the outer ear, sound waves start vibrating the eardrum, which is then transmitted to the auditory bones in the middle ear. From there, the vibration travels through the oval window, a thin membrane at the base of the cochlea, to the liquid in the membranous labyrinth. The waves generated in the fluid move the tiny hairs of the auditory receptor cells, causing them to fire.

Exiting the ear, the cochlear nerve carries the impulses to the auditory centre in the temporal lobe, where the sensation of the sound develops. Perceived sounds are further processed by the cortical areas adjacent to the auditory centre.

THE EAR ALSO CONTAIN THE ORGANS OF BALANCE