An image of the inner ear.
http://www.mayoclinic.org/hearing-disorders/how.html
So how do we hear???
The outer ear collects sound waves and carries them through the ear canal and into the eardrum. Then, the sound waves hit the eardrum. This collision causes vibrations in the inner ear, which cause three very tiny bones to move. These bones are called the malleus, incus, and the stapes. The stapes is the smallest of these three. It fits into the oval window, which is the gateway between the middle and inner ear. Then, the oval window vibrates which causes fluid from the middle ear to pass into the inner ear, or more specifically, the cochlea. The cochlea looks just like a snail shell and is essential to our hearing. In the cochlea, the fluid bends thousands of tiny, tiny hair cells that in turn, send messages to the auditory nerve, which then sends messages to the brain.
Because the eardrum is constanlty being hit with different soundwaves, both high and low, the eardrum vibrates.
http://www.glenbrook.k12.il.us/gbssci/phys/mmedia/waves/edl.html
How Do I Get an Ear Infection?
An ear infection can occur when bacteria gets trapped in your middle
ear. The build up of bacteria causes pus to form. Pus is a yellowish-
fluid that is made up of our white blood cells. Our white bloods cells
help fight germs. As the pus accumulates in the ear pressure starts
to build also. This is why we feel pain when we have an ear infection.
When this happens, hearing is dulled because vibrations can't get in as easily.
http://www.kidshealth.org
How to do it at home:
Next, you could represent the workings of an infectious by filling another bowl with shaving cream. By doing this, the rice no longer jumps. This demonstrates why someone with an infected ear cannot hear very well: the fluid from the infection blocks vibrations.
Materials:
2 4" to 20" in diameter sturdy bowls
plastic wrap
shaving cream
uncooked rice
boom box