If I hold a rod of a solid material in my hand at the ½ way point and stimulate it "properly", it will start to vibrate and produce sound.[br]"Properly" means that the stimulation causes the rod to vibrate at its resonant frequency. If you hear a sound, you have done it "properly". In the worksheet below, the rod is made of aluminum. [br]==Click and drag the slider to fix the [b]length[/b] of the rod. [br]==Click on Vibrate Rod to hear the sound that would be produced.

See: [url]http://geogebrawiki.wikispaces.com/Speed+of+Sound[/url][br]This is just a fun applet, but I did check it out. I downloaded and opened Audacity and then went to the YouTube video: http://youtu.be/MJ4GWk5uwMg and actually checked out the frequencies he produced. [br]Directions: [url]http://geogebrawiki.wikispaces.com/Speed+of+Sound2[/url]