The Whirly Tube, also known as the lasso d'amore, corruga tube, corrugaphone, sound tube, musical tube, or Bloogle Resonator, is a musical instrument that consists of a corrugated plastic tube that is swung in a circle to play. In this activity, the students whirl their tubes at different speeds to produce various pitches.
The sound is created by air moving through the tube.
But why does air move through the tube? The answer is found in Bernoulli's principle. Bernoulli's principle states that as the speed of air increases, its pressure decreases. The free end of the tube moves through the air much more rapidly than the end that you are holding. Therefore, the free end experiences low pressure. The relatively high-pressure air in the tube rushes up to fill in the low-pressure area, creating air flow from the end you are holding to the free twirling end.
The sound is produced when travelling air molecules hit the tube's inner ridges and vibrate.
As you twirl the tube faster and faster, the whirling end's pressure is lowered, the air moves faster through the tube to fill the low air pressure area, the vibrations of the air molecules are faster as they hit the ridges, and the pitch increases.
A vacuum cleaner hose or garden hose will not produce a sound since there are no ridges on the inside to make air molecules tumble and bump into each other and cause them to vibrate. Air will rush through the hose but doesn't make sound!
Students will be able to:
- Describe the properties of sound
- Describe what pitch is and how it varies