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Thinking About The Question

How do we make sounds and how do we hear sounds?

Sounds come from things that vibrate. A vibration is something moving back and forth in a regular way. Some things vibrate and make sounds that we can hear. All musical instruments have some part of them that vibrates and makes the musical sound.

1. You can see how sounds are vibrations by building a model of the eardrum. Build a balloon drum by stretching a balloon over one end of a tin can that has both ends open. Working together,stretch the balloon tight and hold it in place by putting rubber bands around the edge.



2. Talk into the drum. Touch the balloon.

a. What does your voice do to the stretched balloon?




b. Can you feel the vibrations?




c. How do you think the vibrations get from your mouth to the drum?



3. Talk into the drum from below, and put paper clip on the drumhead. Can you make the paper clip move?

   

   
   
4. You may notice that the pattern on the Sound Grapher is up and down, like a wave. The drumhead goes up and down too. These vibrations are very fast, and they make sounds we can hear. The Sound Grapher shows a snapshot of the vibrations. The drum you have built is a good model of the eardrum. In this investigation you will also build a model of the vocal cords in your throat. The vocal cords vibrate and make sounds, and the eardrum vibrates when sounds come to the ear.