Your Ear - Marvel of micro engineering

By Al Lowe
Contributor

Your body is made up of a very large number of parts. Some are big, some are small, but one thing is sure - none of them are simple!
Take your ears, for example. You don't really pay much attention to your ears. They stick out from the side of your head, and don't really bother you unless they get frozen. The inside parts are of no great consequence to you, either. That is until you find that you can't hear very well, or your balance gets out of kilter.
Well, those ears of yours are not simple at all. They are extremely delicate instruments. If something does go wrong, and you lose your hearing or your balance, you are in a real predicament.
Inside your outer ear (the part you can see) is a short canal, about 2.5 cm (an inch) in length. This leads to your eardrum (about the size of a dime). Now all sound is made up of waves in the air - high-pitched sound-short waves, low-pitched sound - longer waves. The 'middle ear' is about the size of a sugar cube in volume. It contains three tiny bones, the smallest in your whole body. Because of their shapes, they are called the hammer, anvil and stirrup. To give you an idea of their size, the stirrup is smaller than a raspberry seed.
When a sound enters your ear, it makes these tiny bones vibrate. The sound is amplified by these bones and that makes the eardrum vibrate. On the other side of the eardrum is a structure called the cochlea. This is a tube, which is coiled up, and is about the same size as the eraser on the end of a pencil. These vibrations go through a fluid inside the cochlea. The cochlea is lined with tiny hairs, maybe 30,000 of them, and they are not all the same size. These 'nerve' hairs bend according to the frequency of the vibrations. In turn, these set up impulses which carry information to your brain - to tell you what kind of sound it is - high-pitched or low, speech or music, grunt, growl, whistle - whatever.
But your ear also takes care of your balance, too. Here is another tiny structure (miniaturizing - long before nanotechnology). This structure consists of two bulbs, and three "semicircular canals". Each of these canals widens at the base, to form another tiny bulb. Inside of each bulb is a group of very tiny hairs, covered by a cap of jelly. When you move forward, the fluid presses against the cap. The tiny hairs bend back. Nerve impulses from here tells your brain that you are moving forward. Actually, the jelly-like material contains very fine particles of calcium carbonate, called ear-stones. They, and the jelly, bend the tiny hairs, which then triggers your brain, to tell you what to do, to keep your balance.
Another thing. Attached to you middle ear is a small tube, which goes to the upper part of your throat. Air comes through this "Eustachian Tube", so that the air pressure, in your middle ear, and in the outside world, can be the same.
Your ear is a real marvel. Here are a few facts about it.
Your ear uses only about 14 micro watts of power. It could run for about 15 years on one AA battery - the kind you put in your camera.
Your ear can distinguish sounds from almost zero to about 120 decibels. That means anywhere from the rustle of a leaf in your garden, to the sound of a jet engine nearby.
Your ear can pick out one conversation in a whole room full of people talking.
No artificial system, so far in our lives, has even come close to these.
How's that for micro engineering!