Ruben's Tube

The Ruben's Tube Experiment was designed by Heinrich Rubens. This project shows the correlation between sound wave and sound pressure. We will measure the sound waves by examining the different heights of flames we could reach. However, it has been replaced by modern sound wave measuring utensils.

Materials

1.) Long Metal Tube (with holes over it)

2.) Gas Pipe

3.) Gas Cylinder

4.) Speaker Wire

5.) Speaker

6.) Hose

7.) Stands for the Ruben's Tube

8.) Lighter

Procedure

1.) The aluminum tube must be hole-side-up, on its stand.

2.) We will connect a propane gas container next to it and connect it with a gas pipe into one side of the tube.

3.) On the other side of the tube we will strap a rubber membrane unto it. and tightly confine it.

4.) A speaker will be placed right next to the plastic membrane.

5.) After ensuring everything is correctly secure and tightened. We will turn on the propane gas at about 5 cm.

6.) Right after this, we will light the holes on the tube.

7.) We will begin playing a sound on the speaker.

8.) Finally, you can enjoy watching the flames dance to the rhythm.

Scientific Principle

The project is explained by Bernoulli's Principle. It explains that the flames height is proportional to the gas flow, while the gas flow is equal to the square root of the pressure difference between the inside and outside of the tube.

Since the time averaged pressure is equal at all points of the tube, it is not straightforward to explain the different flame heights. The flame height is proportional to the gas flow as shown in the figure. Based on Bernoulli's principle, the gas flow is proportional to the square root of the pressure difference between the inside and outside of the tube. This is shown in the figure for a tube without standing sound wave. Based on this argument, the flame height depends non-linearly on the local, time-dependent pressure. The time average of the flow is reduced

at the points with oscillating pressure and thus flames are lower.

The varying heights of the flames follow according to the frequency of the wave. Each frequency creates a different

harmonic. 1st harmonic, 2nd harmonic, 3rd harmonic...

Each of these harmonics have nodes and antinodes. The nodes are the "empty spaces" that create a lower

flame height.

All experimentation will be done with a fire blanket and a fire extinguisher in the area. Adult supervision is required

*Children must use this only with an adult present*