The Ruben’s TubeStanding Waves in Music

What is it??

A Ruben’s Tube is a metal pipe sealed at both ends; one by inserting a flammable gas, and the other with a speaker. The pipe is lined on top with uniformly sized and equally spaced holes. These holes allow a flammable gas to escape which are then lit on fire.

GasSpeaker

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• Each frequency will cause the flames to form a different shape due to the resultant difference in wavelength that occurs when the frequency is changed.

• Music is composed of changing frequencies, this causes the flames to “dance” when music is played through the speaker of the Ruben’s Tube.

• Use the following link to see a Ruben’s Tube in action (with a variety of music!): https://www.youtube.com/watch?v=gpCquUWqaYw

So how does it work?When the speaker is turned on sound waves are produced through the tube. Sound waves are longitudinal which means that they have areas of compression (high pressure) and rarefaction (low pressure). Due to the fact that the waves are reflecting off the ends of the tube, interference is occurring which causes a larger flame in areas where constructive interference is occurring and smaller flames in areas of destructive interference.

High Pressure

LowPressure

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A pipe with a length of 1.75m is used to make a small Ruben’s Tube. What is the

fundamental frequency of the wave if the velocity of the wave is 316m/s?

Solution

ƛ1=2L

L=1.75m

v=316m/s

So.....

f1=v/ƛ1

f1=v/2L

f1=(316m/s)/

2(1.75m)

f1=90.3Hz

Consider a frequency of 542Hz being played through the speaker of the Ruben’s Tube from the previous question (L=1.75m,

v=316m/s). What is the mode?

Solution

v=316m/s

f=542Hz

L=1.75m

ƛn =2L/n

So.....

f=v/ƛ

f=vn/2L

n=2Lf/v

n=(2*1.75m*542Hz)/(316m/s)

n=6