Re: speed of sound experiment

[John Gastineau <gastineau@mindspring.com>]

Great idea with the billiard balls. 

Regarding the open pipe length effects, here's a way to investigate this
rapidly: 

Rather than looking at the time domain, go to frequency. Take a set of
tubes, running from the cardboard inner from a roll of toilet paper, paper
towel tube, gift wrap paper tube, packing tube, etc. Use the MBL (can't
use cbl this time) and set it to show the FFT of the sound generated by
thumping the side of the tube. The lowest frequency in the spectrum (not
always the most intense, but often) is the fundamental unless you are very
unlucky in exciting exclusively harmonics. 

> From the fundamental frequency find the wave speed. The TP tube gives
horrible numbers since it's all end effects. 

Back to my original post with the CO2, if one is careful to only compare
one closed end to one closed end conditions, and since the gas mixture
near the top of the tube is going to be essentially that of the room air,
the change in speed due to gas mixture is still clearly detectable. 



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John E. Gastineau      gastineau@mindspring.com               KC8IEW
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