Glass Bottle Orchestra

A colourful melody, a concerto in B... or is it C? You decide, as you become maestro of your very own orchestra!

Australian Curriculum links

  • Science > Physical Sciences > Year 1 > ACSSU020
  • Science > Science as a Human Endeavour > Year 1 > ACSHE022

You'll need

  • 8 identical glass bottles
  • water
  • food colouring
  • 2 pencils, wooden sticks or xylophone mallets

Try this

  1. Fill each bottle with a different amount of water.
  2. Add food colouring to make the water levels visible.
  3. Use the pencils to tap the glass bottles.
  4. Observe which bottle makes the highest sound and which bottle makes the lowest sound.

What's happening?

When you tap the bottle, it makes the glass start to shake or vibrate very quickly. This vibration makes the sound we hear. Adding water changes the speed of the vibrations, which changes the pitch of the sound.

All sounds are made by vibrations. A vibration is simply something moving backwards and forwards. Fast moving vibrations make high pitch sounds like a whistle and slow moving vibrations make low pitch sounds like a lion's growl.

Adding water to the glass bottles slows down the vibrations in the glass. This makes the pitch lower. As you continue to add more water the vibrations become slower so you get an even lower sound.

Real world links

The lowest sound waves ever heard come from a black hole. The black hole is in a distant cluster of galaxies named the Perseus Cluster and is located 250 million light years from Earth. Astronomers have been able to detect sound waves from it in the form of a single note—apparently in the key of B flat in 57 octaves below middle C! Many people believe that space is a pure vacuum and that sounds in space can not be heard because they have no medium through which to travel. However, space is not a pure vacuum. The sound waves coming from the black hole are hitching a ride on the dust and gas atoms that do exist in varying amounts in the galaxies. For more information about space and this 'singing black hole', visit the NASA website.