| MadSci Network: Engineering |
Good Question! First: A string telephone works because the sound vibration from your voice is resonated mechanically by some device (like a tin can or paper covering a cardboard tube). The resonator is called a "diaphragm". The vibration is then passed along a string. Then the vibration from the string is mechanically converted back to a voice-like sound by the diaphragm at the other end. Second: When I was a kid, we made string phones with tin cans (like a soup can). The example below is made with a cardboard tube. You might want to explore the differences in sound fidelity (the clearness of the voice) between these two materials. Third: Make sure the string is tight. Remember that the string has to vibrate to "record" the sound of your voice. If the string is too loose, the vibration energy will be lost. This also applies to making the string too long. (In real-life telephone wires, computer networks, and electrical power wires, there is the same problem. To solve the problem, the signal is periodically "boosted". That is not practical using a string telephone.) Fourth: Here is an example of a string telephone that I found on the net at the following address: "http://voyager.snc.edu/Mythological%20Look/String_Telephone.html" PROCEDURE 1: Build your own "string telephone." (1) Fold a piece of tracing paper over one end of each of your cardboard tubes. Hold it in place by putting a rubber band around it. (2) Pull the paper tight and secure it with some tape. (3) Using the lead end of a pencil, poke a small hole in the tracing paper that is connected to your tubes. Do this for both tubes. (4) Insert string into the holes in the tracing paper of each tube. Once each tube is threaded, tie a paper clip to the end of each string so the string does not slip through the tubes. (5) Your "string telephone" is now complete! Good luck on your project! Mac Salfen fussweg@aol.com
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