Your ear and hearing

The world would be a very different place without your ears!  You could see things but not hear them, so you would miss out on a lot of very important information.  If you cannot hear the volume and tone of a voice or the beeping of an alarm, it can be more difficult to understand, to learn or to be alerted to danger.  Try to imagine what it would be like if you couldn’t hear.  Put on some ear muffs, or even just pull a woolly hat down over your ears and see what its like.  Isn’t life more difficult?

Sound travels in waves through the air.  These are like little vibrations that travel through the air and are picked up by your ears.  Your ears gather up all of the sound waves around you and send the vibrations as signals to your brain, which then figures out what the sound is.  But how do they do this? 

Your ear is made up of three main sections – your outer ear (its called the pinna), your middle ear and your inner ear.  These are all connected and transfer the sound waves from outside to your brain, which figures them out.

Your outer ear

The shape of your pinna (your outer ear) is very good at making sure all of the sound waves around you are collected.  Next to this is your ear canal, the main channel into your middle ear.  Sound waves travel along your ear canal and it is also where earwax is made.  Earwax is pretty sticky and nasty but it does a very important job.  Not only does it keep your ear canal clean by catching dust and microbes that try to get into your ear, it also has chemicals that fight any microbes that enter your ear canal.  Remember always to get an adult to help when you are cleaning your ears and your ear canals because it is very easy to damage the delicate tissue inside your ear!

Your middle ear

At the end of your ear canal is your eardrum.  This is a really thin piece of skin that is stretch across the ear canal.  If you could see it, it would look like a drum you see in a band!  It is very smooth and tight and when sound waves hit it, it vibrates.  This vibration transfers the sound waves from outside into your middle ear, where there are three tiny bones that transfer the sound waves even further.  The three bones are your hammer (malleus), which is next to your eardrum; the anvil (incus) which is next to your hammer and the stirrup (stapes) which is next to your anvil.  Most people call these the hammer, anvil and stirrup but their proper names are the malleus, incus and stapes.

When sound waves reach your eardrum, it vibrates.  The vibrations are transferred to your malleus, the first of these small bones.  It vibrates and causes the incus and then the stapes to vibrate and the sound collected by your pinna gets closer to your brain!

Your middle ear has one more very important job.  Have your ears ever popped?  This can happen if you are taking off or landing in an aeroplane or if you are moving up or down a mountain.  When you get high up, the air pressure changes and you have to make sure that the air pressure inside your ear changes too!  This is fine for your lungs, which are changing air all the time, but is more difficult for the air in your ears because they are in a more closed-in space.  Luckily, you have an ‘air valve’ in your ears.  At the back of your nose, there is a tube, called the eustachian tube that is connected to your middle ear.  If you swallow or yawn, this tube opens and the air pressure on the inside of your ear changes to the same pressure as the air on the outside of your ear.  If the air pressure is different inside and outside your eardrum, it can be very painful!  This is why it is best to suck on a sweet (so you swallow lots) or to yawn a lot when you are taking off or landing in a plane!

Your inner ear

Your inner ear is the last stage for sound waves on the journey to your brain.  When the vibrations leave your stapes, they enter your cochlea.  This is a tiny tube that is curled up really tightly in your inner ear.  Your cochlea is filled with liquid and with tiny hairs that move when vibrations reach them.  The movement of the liquid and hairs in your cochlea sends nerve signals along your auditory nerve to your brain.  Your brain then changes these vibrations into sounds you recognise! 

All of this happens so quickly, from the time you hear the sound to the time you know what they are, that you cannot hear any gap – everything happens immediately!

Your inner ear has another equally important job – it tells you which way is up and stops you from falling over!  Just above your cochlea, there are three small loops called you semi-circular canals.  Like your cochlea, they are filled with liquid and have very tiny hairs inside them.  Every time you move your head, the liquid and hairs in your semi-circular canals move too.  Nerve signals are sent to your brain and your body knows what muscles to use to stop you from falling over!  This doesn’t happen all of the time, especially if you are moving quickly, so just because you fall over doesn’t mean that your semi-circular canals aren’t working!  Imagine you spin around very quickly.  When you stop, do you feel dizzy?  This is because, even though you have stopped, the liquid in your semi-circular canals hasn’t, so your brain still thinks you are moving!  The problem is, your brain also knows that you have stopped so it is totally confused!!  It manages to fix itself pretty quickly, when the liquid in your semi-circular canals stops moving, but until then you will have to work very hard not to fall over!

What about problems?

Some people have a lot of problems with their ears, which is very frustrating.  You can get an idea of what it feels like if you have a cold and your eustation tube gets all blocked up.  You might only be able to hear very loud sounds or sounds that are very high, like an alarm but anything else sounds muffled and very far away?  Sometimes lots of wax can get stuck in your ear canal (your doctor can help to fix this) or you may have accidentally put something in your ear canal that’s gotten stuck (again, your doctor can help to fix this).  These problems make it more difficult to hear sounds but they are easy to fix – the best thing is not to put anything smaller than your elbow near your ear!

Do you know what the most common reason hearing is damaged?  It is noise!  If a sound is very loud, the sound waves it makes are very strong.  As the sound waves travel through your ear, the vibrations can cause your eardrum or the tiny bones in your middle ear to shake too much and become damaged.  You might hear a ringing in your ears for a couple of days or your ears may be a little painful – this means you have damaged your hearing.  This damage usually gets better pretty quickly but it is best not to let it happen to often as a little bit of damage again and again can lead to big problems when you are older.

What if your hearing is damaged and it doesn’t get better?  A small machine called a hearing aid can help some people who have a problem hearing properly.  It doesn’t work for everyone, but it can be helpful for some people.  The hearing aid is like a microphone, it makes sounds louder so they are easier to hear.  Sometimes though, other sounds happening at the same time can cover the sounds the person wants to hear.  In a crowd, the noise of lots of people talking can be a distraction, so lots of people with hearing problems also learn to lip read – they can tell what you are saying just by looking at your lips move!

Some people cannot hear from the time they are born, so they never know what a voice or a bird singing or a car engine, or anything sounds like!  This can make it very difficult for them when they learn to talk, because they have never heard anybody talk – its trying to learn the piano without having any lessons or any sounds to hear if you are doing okay!  It is very difficult and can mean that people who have hearing difficulties sound a little different to people who do not when they speak.  You can help someone who has hearing difficulties by making sure you know the person is looking at you and speaking clearly without covering your mouth or lips.  You could also learn sign language – a special type of talking with your hands – so that you can understand and be understood no matter how many other people are talking!

Did you know…?

Hearing difficulties don’t stop many famous people from being the very best at what they do!  Ludwig von Beethoven, a really famous classical music composer, never heard a lot of his music as he wrote a huge amount of it after he had totally lost his hearing!

Sound is measured in decibels. Sound is quite special because you cannot just add one sound to the next like you do in maths class.  If you have a sound like someone talking that is 40 decibels and a sound from a radio that is 70 decibels – the total sound isn’t 120 decibels but just a little more than the louder sound.  Your ears will start to hurt at about 90 decibels so just be careful how much sound you add together!