This little experiment is great for looking at sound vibrations and their effects on pitch...prepare your ears for a bit of a racket!
What you will need
- 1 balloon
- M8 Hex (Hexagonal) nut - small objects present a choking hazard for young children so be careful with this experiment if there are any little people around (please note: M8 nuts work well for this experiment (smaller nuts give a higher pitched noise). If these are unavailable, try a 20p piece.)
How to do it
- Place the hex nut inside the balloon.
- Fully inflate the balloon and tie off the neck.
- Hold the balloon by the neck with the body pointing downwards.
- Twirl the body of the balloon in circles to get the nut spinning.
What is happening?
The corners of the nut hitting the balloon’s wall produce a little noise. When this is repeated thousands of times a minute, it sounds like a strange whirring noise. Change the speed of your twirling. What happens to the pitch of the sound?
The corners of the nut bounce as they hit the balloon and cause it to vibrate, or move back and forth very quickly. As the balloon vibrates, it in turn vibrates the air molecules nearby which creates sound waves. The faster the balloon vibrates, the faster the frequency of the sound waves and the higher the pitch will be. As the nut moves faster it also has more momentum and makes the balloon move farther with each vibration, which pushes more air and makes the sound louder.
Share your experiment...
All experiments must be conducted in the safest possible way. An adult must be present wherever it states one is required. Never do anything dangerous with chemicals or fire for your sake and those around you.