How we hear

To understand hearing loss, it helps to understand how hearing works. Your ear is an amazing organ that can perceive sounds from barely audible to very loud and can pinpoint the direction of a sound source to a surprising degree of accuracy.

The human ear consists of three parts:

The outer ear includes the visible part of the ear (pinna) and the ear canal.

The middle ear is in an air-filled cavity separated from the outer ear by the eardrum.

The inner ear contains the cochlea, which is a snail like organ filled with fluid and contains thousands of tiny nerve fibres.

When we hear sounds waves collected in the pinna travel down the ear canal to the eardrum (tympanic membrane). These sound waves set the eardrum into vibration.

The middle ear contains the three smallest bones in the human body, the ossicles. These bones vibrate along with the eardrum and convert sound waves into mechanical energy.

The mechanical action of the ossicles creates movement in the fluid and stimulates the nerve fibres. The nerve fibres send electrical impulses along the auditory along the auditory nerve to the brain, which interprets these impulses as sound.

The loudness of sound is measures in units called decibels, abbreviated ‘dB’. After a hearing test, the level of hearing is displayed in a chart called an ‘audiogram’. An audiogram expresses the relative intensity of sounds on a scale from for the average least perceptible sounds to about 100dB, which is near the level most people find uncomfortably loud.