VOLUNTEER TRYING TO TEACH: The Partyorgan Ear

Context

SCIENCE/ Sense organs

Jokers of interest

A very colourful poster

Activities and experiments in front of the class

Materials

LESSONS

The ear is the sense organ for what? For hearing sound, music, noise!
But what is sound? When we sing, dance, speak of make noise, we produce vibrations/ sound waves in the air: You can feel your throat vibrating when you touch it while you are speaking. Can you all touch your throat, saying AAAAA?
this vibrations of the throat cause vibrations in the air, sound waves! We can not see them, but they are all around us, when ever we make noise! You can imagine it like water waves in a basin. Every wave transmits a different sound.

The pinna is for catching all this sound waves (I show the learners a funnel) – it puts them all together in the ear canal (approx. 3 cm long)
At the end of the ear canal, there is the eardrum. (I point at the bit of paper at the smaller end of the funnel)
I think you all know what a real drum is like. Can you all drum some rhythm on your desk?
The ear drum works almost the same as a drum. When the sound waves reach the ear drum, they hit against it like you do with your hands on the table. But the ear drum is not like a wood table, but it is only a thin membrane, a thin layer of skin. When it gets hit by the sound waves, it starts vibrating heavily and by this, passes the sound waves further on into the middle ear.

right now, the sound waves are too low, too poor, too weak for us to hear them
but behind the ear drum we have a really smart mechanism (a trick) to increase the sound waves, to make them 22 times stronger than before!
The trick consists of three little bones – the smallest bones in your body! – they are called hammer, anvil and stirrup and they work together like three good friends.
Can I have three really good friends of you here in front? (I give each one a sign with the name hammer, anvil or stirrup)
(I put my hands on the shoulders of the learner with the sign saying “hammer” and start shaking him.) Now, when the hammer recieves the vibrations of the ear drum, he passes them quickly to the anvil (the learner “hammer” is supposed to shake the learner “anvil”), and the anvil passes them very fast to the stirrup (“anvil” shakes “stirrup”), and now the stirrup throws them out of the window!

the oval window is the connection to the inner ear
in our inner ear we have something like a snail. This snail is filled with some fluid and has little hairs, smaller than the ones on our arms all along it´s length.
When the stirrup pushes the sound vibrations through the window, he hits against this fluid in the inner ear – the fluid starts shaking and vibrating and by this, the hairs in the snail are moved. (I stroke the hairs on my arms and tell everybody to do the same) The hairs belong to sensory cells. When they get moved, the sensory cells will notice and pass the information to the brain. And that is the first time when hear the sound!
There are differences; when the hairs in the snail are pushed harshly, we hear a louder sound than when they are pushed more softly. The hairs can be pushed more outward or more inside of the snail – that makes higher or deeper sounds.

Did you know that the ear is not a sense organ only for hearing sounds, but also a sense organ for movement of our body and changes in position of the body?
just above the inner ear snail, there is another tool of our ears, called the semi-circular canals! They look they three loops, two in upright position and the third flat on its side
they are also filled with fluid. When we spin our body around, the fluid in the flat loop-canal gets shaked a lot and tells our brain that we are spinning our body around! Even if we stop, we will feel shaky, because the fluid in our ears is still spinning. (The learners shall experiment this!)
When we make a forward roll, the fluid in one of the upright canals gets shaked a lot and tells our brain that we are making a forward roll!
When we are making a sideward roll, the fluid in the other upright canal gets shaked!

Have you ever felt ear pressure when you travelled down a long hill in a car for example? At a while, the ear will `pop´ and we hear freely again
That´s because we have a connection between our throat and our ears, called the Eustachian tube. The entrance of the Eustachian tube is in the middle ear, right below the three friends hammer, anvil and stirrup
When we swallow or yawn, we open the Eustachian tube and air can enter or leave the middle ear – the pressure on either side of the ear drum can be made the same!

I tell 4 children to come in front, one of them stands in the middle and closes the eyes. I point to one of the children to clap in the hands and the learner in the middle has to tell the class where the sound came from – we repeat it three times, then I ask the class: how does he know?
It is only possible because we have two ears! When the sound comes from in front, the sound waves reach our both ears at the same time. But when the sound comes from one side, the sound waves reach one of our ear earlier than the other one. That´s how we can say from which direction the sound has come!

VOLUNTEER TRYING TO TEACH