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How We Hear

How do we hear?

The human ear is amazing! It’s a finely tuned organ which works really cleverly to allow us to enjoy the sounds and conversations around us. If you think about it, the ear connects us with people. If we can’t hear, we can’t find out about our partner’s day, hear the grandchildren excitedly sharing their school news or enjoy a TV program.

Like any part of the body, we need to look after it and if something starts to go wrong, take action sooner rather than later. But first, let’s look at how the ear actually works.

The ear is made up of 3 very important parts:

  1. The outer ear
  2. The middle ear
  3.  The inner ear

Each part of the ear has a specific role in making the sound we hear meaningful. For example, picking up the pitch of a bird in the tree and transmitting it all the way to the brain where you can recognise it as ….a kookaburra.

The outer ear

The outer ear is basically the part of the ear we can see. The physical ear as we know it is called the pinna and the ear canal is the opening into which sounds travel.

The bowl shape of the ear is designed to pick up sounds from in front of us rather than behind us. Therefore, when we visit a noisy place (such as a restaurant), the ear naturally tries to stop the background noise from behind us so we can focus on the person in front of us. Also, the pinna lets us know which direction a sound is coming from. This is very important – especially in traffic or outside.

The ear canal is made up of 2/3 cartilage and 1/3 bone and acts as a channel to let the sound pass through to the eardrum.

The middle ear

The middle ear is essentially a vibrator. Depending on the loudness and pitch of a sound, the vibrations quiver.

The eardrum itself is a piece of skin which moves with the sound in the ear canal. For example, if it’s a loud sound, the eardrum movement is big and if it’s a soft sound, the eardrum moves quite gently. If the sound is high pitched like a flute, the eardrum moves very quickly. If it is a low pitched sound like a drum, the eardrum moves slowly.

Sound is passed onto the three middle ear bones – the malleus, incus and stapes. These three bones all vibrate onto a small membrane leading to the inner ear called the oval window.

The inner ear

The inner ear is called the cochlea and is shaped like a snail shell. The cochlea is filled with fluid and this fluid bathes the millions of tiny hair cells attached to the walls of the inner ear.

As the sound passes from the outer to middle ear, a big wave of fluid moves along the cochlea and bends the hair cells. If you can imagine a wave in the sea moving the seaweed underneath, this is pretty much how it works.

This wave stimulates the tiny hair cells to create an electrical impulse which is then passed onto the nerve of hearing.

So how does the inner ear work out the pitch and volume of the sound? Again, it is pretty amazing.

Remember, the cochlear looks like a snail shell. At the start it has hair cells that are coded for high pitched sounds. In the middle of the shell there are hair cells coded as mid-pitched cells. All the hair cells at the end of the snail shell are coded as low pitched cells. So if you are listening to a bass guitar, the wave of fluid washes all the way to the bottom of the cochlea to stimulate the low pitched hairs.

Just imagine how complex this is when listening to speech or music which have a huge variety of low and mid pitched sounds. We think it’s incredible!

The last part of the hearing chain involves nerve fibres which sit underneath the hair cells. These nerves pass the message through the auditory nerve to the hearing part of the brain called the auditory cortex.

The brain then uses our memory and our knowledge, as well as all our senses, to make that sound meaningful.

See this helpful video which shows how we hear.

Our hearing connects us

Our hearing connects us with life:

It’s so important to treat your hearing like a precious gift so act sooner, rather than later, if you notice a problem.

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