I did a variation on a speed of sound experiment tonight that I thought
I'd share. The basic experiment is to use a microphone and a CBL, MBL, or
memory oscilloscope to record the echoes of a short sound as it bounces
back and forth between the ends of a packing tube.
One of you (thanks, Kyle) suggested trying the experiment with another
gas. Well, homebrewer that I am, I went down to the kitchen and took the
CO2 cylinder, and "poured" CO2 into a vertical tube with the bottom
sealed. I got a 10% change in speed, and I estimate the measurement
uncertainty to be only a few percent. Now, the speed of sound in CO2 is
actually about 30 or 40% faster than in air, but I'm sure I didn't have
the tube full of just CO2. All I did was pour.
Anyway, I didn't think it would work, but it did. Neat.