My Science School

In noisy places, you have to listen hard to hear things. You may put your hand to your ear to catch the sounds. Sometimes you use your hands to help your ears. Some people’s ears need help all the time. These people are hard of hearing. Some other people cannot hear at all. They are deaf.

People who are hard of hearing may wear a hearing aid. A hearing aid makes sounds louder. It may allow people who are hard of hearing to use a telephone or hear more clearly the things people say. But hearing aids cannot help people who are completely deaf.

Some people who are deaf may have a cochlear implant.

A cochlear implant is an electronic device that a doctor attaches to the head just behind the ear. The implant picks up sounds, converts them to electric impulses, and sends the impulses to a nerve in the brain that allows us to hear.

Deaf children and children who are severely hard of hearing have a hard time learning to speak. Normally, children learn to speak by listening to others. But deaf children cannot hear. Many people who are hard of hearing use lipreading or sign language to “talk” with other people. When they lipread, they watch the speaker’s mouth to see what the person is saying. In sign language, hand signals stand for words. Some people who are hard of hearing can learn to speak. They use little or no sign language. Instead they speak in speech-read to talk with others.

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You hear things-people talking, car horns honking, and dogs barking. You know what these sounds are because your ears and brain work together.

When something makes a sound, the air around it moves, or vibrates. The vibrations travel through the air as sound waves. The sound waves enter your ear and bump against your eardrum. When the sound waves hit it, your eardrum moves.

When your eardrum moves, it bumps into three small bones. As each bone bumps the next, the third moves in and out of an opening in another part of the ear called cochlea. The cochlea is shaped like a shell.

Inside the cochlea are liquid and nerves. As the bone moves in and out of the cochlea, it makes waves in the liquid. The waves move across the nerves. The nerves carry messages to your brain. Your brain tells you what sound you are hearing.

How well do you and your friends know the sounds around you? Make a tape recording of different sounds you hear every day, such as your parents talking, a car starting, a door closing, computer turning on, a toilet flushing, a clock ticking, and a dog barking. Leave a moment of silence between each sound. After you have made your recordings, ask your friends to listen to each sound on the tape. See if they can guess what the different sounds are. If you do not have a tape recorder, you and your friends can take turns making sounds. Get your friends to cover their eyes as they listen to you making different sounds. You might pour water, crumple paper, and open an umbrella.

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Take a deep breath. Now let it out slowly and say “Ahhhhh”. You will only be able to make this sound while there is air in your lungs. When you run out of air, there will be no sound. This shows you how important your lungs are for talking.

Have you ever notice the small bump on your neck beneath your chin? That’s your voice box, or larynx. Your larynx is like a box with two pieces of tissue stretched across it. The pieces of tissue are your vocal cords. When you talk or sing, air from your lungs is pushed through the opening between your vocal cords. This makes your vocal cords shake, or vibrate, they make a sound.

By using muscles to change the size and shape of the spaces inside your mouth and throat, you can make all kinds of sounds. You can talk and sing. You can even bark like a dog.

See for yourself how the voice box works. With an adult‘s permission, blow up a balloon. Then pinch the neck closed, so no air escapes. Do you hear anything? You should not. Now stretch the neck of the balloon to make a narrow slit. What do you hear? As the air escapes, it makes a squealing sound.

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Sometimes eyes need help to see well. When you go to your optician for a checkup, he or she checks your eyes. You read a chart from across the room. If you cannot read the chart very well, your eyes might need help.

Eyeballs should be nearly round. People whose eyeballs are too long are shortsighted. Close up, they can you see things well. But if they look at an object that is far away, such as a far-off house, they see a blur. That’s because a clear picture of the house does not form at the back of their eyes. Short sighted people wear glasses or contact lenses to help them see things that are far away.

People whose eyeballs are too short or long sighted. They can see things in the distance well. But when they look at something nearby, such as the words in a book, they see a blur. A clear picture of the words does not form at the back of their eyes. Long sighted people wear glasses or contact lenses to help them see things that are nearby.

Some people wear contact lenses instead of glasses. Contact lenses are made of clear plastic. They float over the irises on the tears that cover the eyes.

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Sight maybe you are most important sense for finding out about the world around you. Your eyes work with your brain to help you see.

When you look at something, light bounces off it and enters your eye. The light travels to the back of your eye, to a nerve called the optic nerve. The optic nerve carries messages about the light to your brain. When your brain gets the messages, you know what you are seeing.

The coloured circle on your eyeball is your iris. In the centre of your iris is a dark spot. That is your pupil. Your pupil is a hole that lets light into your eye. Muscles in your iris make your pupil bigger or smaller to let in more or less light. The darker it is around you, the larger your pupil gets. The brighter it is around you, the smaller your pupil gets.

Tears come from little holes behind your eyelids. They bathe the outside of your eyeballs. They clear your eyes of dust and hairs. They also keep your eyes wet.

You can watch your pupils get bigger and smaller. It’s easy. All you need is a lamp and a hand-held mirror. Stand in a part of the room away from the lamp. How big are they? Now stand close to the lamp. Look at your pupils again. How did they change? Did they get smaller? What do you think would happen if you moved away from the lamp again? Try it.

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