The Ear

Together, the auricle (the area in front of the eardrum) and the outer ear canal form the only part of the ear that we can see. The outer ear is shaped so that oscillating air that arrives is amplified and structured to prevent wind and other air movements from causing intense background noise. The outer ear is where sound waves first arrive, and from here, they are funnelled inwards through the auricle to the middle ear. 

The area behind the eardrum is called the middle ear. The eardrum itself is a thin membrane stretched like a drum that is hit by sound waves that are transported to three tiny little ossicles (tiny bones) named after their shape: the malleus (hammer), incus (anvil) and stapes (stirrup). These ossicles are the smallest bones in the human body and can amplify sound up to twenty times because of their location. The tiny stapes bone attaches to the oval window that connects the end of the middle ear to the beginning of the inner ear. The Eustachian tube (a narrow passage leading from the pharynx to the middle ear cavity) is responsible for ventilating and equalising pressure between the air outside and air within the middle ear.

Within the inner ear is the cochlear, which is approximately the size of a pea and resembles a snail shell. The cochlear contains three canals filled with liquid; via one of these canals, the signals conducted into the liquid are directed to the tip and back via a second canal. 

The central canal is home to The Organ of Corti (the actual organ of hearing), which is covered in thousands of tiny hairs.

Within the inner ear is the vestibular organ (responsible for your balance) and the cochlear, a snail-shaped organ approximately the size of a pea. The cochlear contains three canals filled with fluid that moves in response to the oval window's vibrations. It also includes a tiny structure called the organ of Corti (the actual organ of hearing) covered in thousands of tiny hairs (hair cells). Wave movements in the canals change depending on the frequency and are only triggered when the amplitude is particularly significant. Deeper tones move the hairs cells located further back in the cochlear, while higher tones trigger hair cells at the beginning of the cochlear. As you get older, these tiny hairs wear, which is one of the main reasons for age-related deafness.

When sound waves arrive in the inner ear, they still do not have meaning. Sound waves that arrive at the auditory nerve are converted into electrical signals that then hit the brain stem. These signals are transported to the brain areas responsible for emotional assessment and assigned meaning connected to existing tones and patterns in the cortex. Transporting these signals allows us to understand speech, recognise the voice of a friend and judge situations. 

Our hearing only works if we can transport signals from one station to another, and only once oscillating air has been turned into a sound or tone that we can understand.