CAMS390 · Music

Time to calculate!

Calculating Standing Waves in an Open Tube:


where v = the speed of sound,
f is the funadmental frequency, and
λ is the wavelength.


To calculate the wavelength:


Where L is the length of the tube in meters.

To calculate the resonant frequencies for the length of the tube:


Where n is the resonant frequency number, making f(1) the fundamental frequency

Now, a ruben’s tube has a closed end, so the calculations differ slightly from that of an open tube.

To calculate the wavelength:


therefore to calculate the fundamental frequency, the formala is:


Assuming that we are using propane gas (LPG) for the fuel of the ruben’s tube, v is the speed of sound in propane (248m/s).  Therefore, if we know the fundamental frequency we wish to achieve.  Let’s assume our fundamental is A4 (440hz), we can determine the ideal length of the Ruben’s Tube with the formula:




A tube length of 0.14569m would display a single arc when A4 (440Hz) is played into the tube.


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