Deafness may be produced by multiple causes, although the majority is due to problems in the ear. The ear is the organ in charge of hearing in human beings. It is divided in three parts: external, middle, and outer ear.
The outer ear is formed by the visible part of the organ; the ear and the ear canal. It is very difficult for a person to become deaf by having problems in the area. Generally speaking, the excessive accumulation of wax makes hearing more difficult but it never causes deafness.
The middle ear is mostly composed of tiny bones. It begins in the eardrum, the membrane where the sound waves bounce off of. The vibration is transmitted towards a series of bones – the hammer (malleus), the anvil (incus) and the stirrup (stapes) — (named like this because of their shapes). They reduce these vibrations and transmit them to the inner ear. Here we find the Eustachian Tube. It communicates with the nasobuccal cavity through which excess pressure is relieved. (This is why it is good to maintain your mouth open when hearing loud noises like explosions or airplanes taking off.)
The inner ear processes the transmitted vibrations of the middle ear by way of two organs: the Canals and the Cochlea. The Canals are responsible for balancing the body; that is why, depending on the severity of the damage, many deaf people may also have a problem with balance. In the Cochlea, the vibrations are transformed into nerve impulses that are sent via the auditory nerve to the brain. This process is carried out by some receptors named stereocilia, that when they vibrate produce a charge that the nerve transports.
In spite of this, the organ that actually hears is the brain; it is what interprets these electrical impulses and deciphers them to distinguish if it is noise made from a motorcycle or music from Bach.
