What it shows
Sound is made by vibrations. A shorter vibrating column of air gives a higher sound, and a longer one gives a lower sound.
The science
Sound is a vibration that travels through the air. When we blow into a flattened straw, its end vibrates and makes the air inside vibrate. A short air column vibrates faster and makes a high note, and a long one vibrates slowly and makes a low note. Flutes and trumpets use the same idea.
Materials
Cost: under Rs 50. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- Four plastic drinking straws
- Scissors
- A ruler
- A new straw for each player
- Paper and pencil
Safety
For this project: An adult must cut the straws. Use a new clean straw for each person and do not share.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
All the safety rulesStep by step
8 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.
Flatten one end of a straw with your teeth or fingers and cut the end into a point.
Put the pointed end in your mouth past your lips and blow hard.
Listen for a buzzing sound. Adjust until you get a clear note.
Keep blowing and ask an adult to snip a small piece off the other end.
Listen to how the sound changes, then snip again.
Write down the length of the straw and whether the sound was high or low.
Make a set of straws of different lengths and join them with tape side by side.
Play a simple tune on your set.
What you should see
Longer straws make lower sounds and shorter ones make higher sounds.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
1What makes the sound in a straw whistle?
Vibrating air.
2What happens to the sound when the straw gets shorter?
It gets higher.
3Name an instrument that works like this.
A flute.
4Why use a new straw for each person?
To keep germs from spreading.
Take it further
Make a pan pipe from straws cut to different lengths and play a tune.
Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.
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