Your Hearing

How the ear functions and causes of hearing Loss

Why we have two ears

Our two ears act as a type of receiving station for the brain. One ear is directed to the left, the other to the right — like radar aerials that register signals coming from different directions. If the ears pick up the sound of a truck approaching, for example, the brain calculates the angle from which the sound has arrived. The brain has this capability since the nearest ear receives the sound a matter of microseconds earlier than the other one.

With only one ear functioning properly, the exact origin of sounds is unclear. Even more important is the fact that the quality of speech is better when it is heard with two ears. Speech received by only one ear sounds flat and devoid of its rich nuances. That is why, in most cases, two hearing instruments are fitted to those with impaired hearing in both ears.

Function and dysfunction of the ear

The ear is a very complex organ comprising three parts: the outer ear, the middle ear and the inner ear. From the inner ear the auditory nerve transmits information to the brain for processing. Hearing loss can result from an obstruction or damage in any of these three parts.

Hearing loss resulting from a problem located in the outer or middle ear is called a conductive hearing loss. A hearing loss caused by a damaged inner ear is called sensorineural. Should the loss be the result of a combination of these, this is known as a mixed hearing loss.

In order to gain a better understanding of hearing loss, it is important to know how the ear functions.

The outer ear

The outer ear includes the auricle (or pinna), the auditory canal and the eardrum. It channels sounds from the surrounding environment into the hearing system. The auricle helps to gather the sound waves and the auditory canal then directs them to the eardrum.

The middle ear

The middle ear is an air-filled cavity which contains the smallest bones in the human body — the malleus, incus and stapes. These are connected to the eardrum on one side, and on the other side to a thin membrane-covered opening on the wall of the inner ear. The middle ear is also connected to the throat via the Eustachian Tube that keeps the air pressure in the middle ear equal to that of the surrounding environment.

The inner ear

In the inner ear the auditory input is processed by the Cochlea, while information affecting balance is processed by the Semicircular canals. Along the entire length of the Cochlea, which is fluid-filled, there are tiny hair cells. When the fluid in the Cochlea is displaced by sound waves that have been passed on through the action of the middle ear bones, the hair cells bend. This triggers a chemical response which activates the corresponding nerve endings. These then transmit the message to the area of the brain in charge of processing and interpreting auditory input.

Click this link to read about why Two Ears are Better Than One