Let's begin our exploration of sound with a solid aluminum rod about a meter and a half long.

Hold the aluminum rod by its center and strike one end with a hammer. The rod will produce sound. After a short while, the sound will become one frequency and that frequency will sound for an amazingly long time. The pure frequency will slowly get quieter and quieter.

Fingers can be used to pinch the singing rod. Pinch the ends of the rod and sound disappears quickly, pinch the center and the sound does not go away quickly. This leads to the discovery of a connection between vibration of the rod and sound.

To learn a lot about sound, all that is needed is an aluminum rod and your fingers!

Ringing Aluminum Rod , Explore the resonances of an aluminum rod.

Visit the Sound Column exhibit. Walk inside a resonant tube closed at both ends. Listen to the resonances produced by a xylophone tuned to the frequencies of the tube. Move your ears up and down to find where the sounds are loud and quiet. At the node of motion near the floor the sound is loud at the antinode of motion the sound is quiet.

An essay

Reflection on an open end, Why does sound bounce off the open end of a tube?


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Scientific Explorations with Paul Doherty

© 1999

25 May 2000