Anatomy of The Ear

Our ears are something we often take for granted and don’t give a second thought, but how do they really work? The outer, middle and inner ear work in sync, to create a hearing system that turns oscillations in the air into signals our brain translates as speech, music and sounds.

The Structure of the Human Ear

Your hearing system is made up of the outer ear, the middle ear and the inner ear, with all three parts being connected via the ear canal, which allows all acoustic systems to pass through. What you usually refer to as your ear is actually the outer ear and is only a small part of your overall hearing system, the larger part of your ear is actually located in, and protected by our skull.

The tones, sounds and speech you hear are actually oscillations in the air. Before these are turned into sounds you can understand, they must travel from the outer ear, through the middle ear, before arriving into the inner ear and the auditory nerve, which then arrives into your brain as a signal.

How Does the Outer Ear Work?

Your outer ear is located in the area in front of the eardrum, the auricle and the outer ear canal. Once the sound waves arrive here, they are guided inwards through the auricle like a funnel.

Your outer ear canal is specially shaped to help amplify oscillating air that arrives, whilst helping to improve your hearing by preventing wind and air movements that can cause strong background noise.

How Does the Middle Ear Work?

Your middle ear is located in the area behind the thin membrane of the eardrum. When sound waves hit your ear drum, tiny oscillations reach the three little ossicles, the hammer, anvil and stirrup (which are the smallest bones in the human body!)

How Does the Inner Ear Work?

Your inner ear starts where the stirrup hits the next membrane, also known as the oval window. This contains the organ of equilibrium and the cochlear, which is a small, snail shell like structure and contains three canals filled with a liquid.

The first canal in the cochlear, directs the signals conducted into the liquid to the tip and back via the second canal. The actual organ of hearing, the organ of Corti is located in the central canal and the bottom is covered in thousands of tiny hairs.

Depending on the frequency, the wave movements in these liquid-filled canals can change, whilst the tiny hairs are only triggered by loud noises. The deeper the tones, the further back in the cochlear the tiny hairs move, whilst higher tones trigger the hair cells at the beginning of the cochlear.

Damage or ‘wear’ to these tiny hairs within the cochlear is one of the main causes of age related hearing loss.

How Does the Ear Send Signals to the Brain?

When sound waves first arrive in the inner ear they still have no meaning. Only when they are conducted to the auditory nerve, are they converted into electrical signals that hit the brain stem.

These signals are then conducted to the areas of the brain responsible for your emotional assessment. This means that meaning is attached to tones connected to existing patterns within the cortex. This allows you to understand speech and recognise the voices of family and friends. Because of this, it means your hearing only works if the signal is sent perfectly from one station to the other and only once the oscillating air has been turned into a coherent sentence or sound.

Air Conduction vs Bone Conduction

Sounds can reach the ear one of two ways, via air conduction or bone conduction. In bone conduction, the oscillating air hits the outside of the skull and makes it oscillate slightly. Conducted by the liquids in the ear, the oscillations then reach the hair cells, however hearing via bone conduction is not as effective as air conduction hearing.

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