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. "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. ==Click and drag the slider to fix the [b]length[/b] of the rod. ==Click on Vibrate Rod to hear the sound that would be produced.
See: [url]http://geogebrawiki.wikispaces.com/Speed+of+Sound[/url] 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. Directions: [url]http://geogebrawiki.wikispaces.com/Speed+of+Sound2[/url]