Everything that moves makes a sound by causing vibrations or movement of air. If you don't believe this, next time Dad is kicked back in his easy chair watching TV, sneak up behind him with two large metal pots and bang them together real hard. Now listen carefully to the whooshing sound as Dad flies out of his chair and runs towards the door. By the way, if Dad offers no reaction to this and instead lies really still, you may have to throw some water on him...
So this vibration or movement of air is the basis for sound. Our ears collect these air movements and change them to nerve signals that are sent to our brain. Our brain interprets these signals as sound.
So what if we could collect more sound waves than normal? Would we have super-human hearing? You bet. In this experiment, we'll construct a sound collector that will allow us to hear Mom and Dad whispering from across the room. If you conducted the mini experiment discussed above, you can also use this device to check Dad for a pulse...
- Take the large sheet of paper and roll it into a cone shape. One end should be as large as possible. The smaller end should should have a whole about the size of a dime.
- Tape the paper so the cone does not come unraveled.
- Hold the narrow end of the cone to your ear.
We interrupt this experiment for a special safety note from Reeko: Do NOT stick the narrow end of the cone in your ear (it can damage your ears). Reeko had a friend name Carl Maloney that once did this. The cone got stuck! Sure, Carl could hear really good after this incident (you couldn't sneak up on him no matter how hard you tried) but he always found it rather difficult to get through narrow doorways.
- Now, turn around the room noting carefully the sounds that you hear.
Our homemade hearing aid works by collecting the sound waves in the large end of the cone and funneling them through the narrow end of the cone into our ears. Since more sound waves are gathered than would normally be possible, you should find that you are able to hear quiet sounds much more clearly. You may notice that the shape of our ears naturally works the same way - they gather sound waves for us!
Parent/Teacher/Advanced Notes [click to expand]
There are two types of hearing aids, air-conduction aids and bone-conduction aids. An air-conduction aid amplifies sound and brings it directly into the ear. Most people who use hearing aids have this type of aid. However, in some people, sound cannot be transmitted through the outer or middle ear. These people often use a bone-conduction aid, which brings sound waves to the bony part of the head behind the ear. The bone transmits the vibrations to the auditory nerves of the cochlea. Hearing is possible when these nerves are stimulated.
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