Trumpeter Makes Fire Dance With Sound

Written by Dan Farrant

Have you ever imagined what it would be like to see sound?

Like actually see it moving through the air?

Well, you don’t have to imagine anymore as this amazing invention called a Ruben’s tube allows you to see sound.

Okay, so you can’t physically see it, but you can see how the sound waves move through the air, and it’s very impressive.

If you haven’t seen one before, a Ruben’s Tube uses fire to demonstrate how the sound waves move through the air by having a series of flames in a long line.

The musician then plays their instrument or a recording into a pipe below the flames.

Picture: Moises Alves

So, how does it work? Well, the Ruben’s tube is a long tube sealed at both ends. One end is attached to a flammable gas like propane, while the other end is connected to a speaker or an instrument.

Along the top of the tube, there are small holes evenly spaced out.

When the tube is filled with propane, the gas escapes through the holes, and the gas is lit to create a row of flames of equal height.

Now, here’s where it gets really cool. When you turn on the music or play an instrument into one end, standing waves are created.

This means there are parts with a lot of vibration and places with less vibration.

This affects the height of the flames, and it’s all because of the pressure differences within the tube caused by the sound waves.

Think about it this way: when the pressure differences are high, the gas in the tube escapes at high velocity, leading to the tallest flames.

But when the pressure differences are low, the flames are shorter.

You can see it in action in the videos below:

The music is lit. Literally.

Photo of author

Dan Farrant, the founder of Hello Music Theory, has been teaching music for over 15 years, helping hundreds of thousands of students unlock the joy of music. He graduated from The Royal Academy of Music in 2012 and then launched Hello Music Theory in 2014. He plays the guitar, piano, bass guitar and double bass and loves teaching music theory.