How Do We Hear?

Sound consists of vibrations of the air known as ‘sound waves’. The ear is able to pick up these vibrations and convert them into electrical signals that are sent to the brain.

The ear consists of three parts: the Outer Ear, the Middle Ear and the Inner Ear as demonstrated in the diagram below.

The outer ear is the visible part of the ear on either side of the head and includes the ear canals that go into the head.  The fleshy parts of the outer ear act as “collectors” of sound waves, which then travel down the ear canal to the eardrum.The eardrm is a membrane of tissue that separates the outer ear from the middle ear.   The sound waves cause the eardrum to vibrate and this vibration is passed on to the middle ear which has a chamber containing three small bones called the “ossicles”.    The energy from the sound waves causes the bones, using a lever action, to channel and concentrate the sound energy down the chain of the ossicles to the smallest bone in the body the stapes .  The stapes, often referred to as the stirrup, pushes the energy onto a second membrane, located on the cochlea, which is part of the inner ear.

The “cochlea” is shaped like a snail’s shell and is found in the inner ear.  It contains tiny cells called hair cells which move in response to the vibrations passed from the ossicles.  The movement of these hair cells generates an electrical signal that is transmitted to the brain via the auditory nerve.  In the brain, these signals are translated into meaningful information, such as language or music with qualities like volume and pitch.

<em>A close up of the Hairs Cells inside the Cochlea</em>

The whole hearing system is extremely delicate and intricate and not surprisingly there are a number of areas where the hearing process can fail or not work as efficiently, unfortunately resulting in hearing difficulties.