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Find out about sound and vibration with this simple experiment.
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Curriculum Links KS2 Sound and Vibration, Materials & their Properties
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Download the experiment guide:
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Video requires sound.
You will need two balloons, a balloon pump, a smooth round object such as a marble or bead and an object with corners such as a hexagonal nut.
You will need two balloons, a balloon pump, a smooth round object such as a marble or bead and an object with corners such as a hexagonal nut.
- Place each object in a different balloon and inflate both balloons with the pump. If you do not have a balloon pump, inflate the balloons BEFORE inserting the objects - it is tricky but possible to do, and much safer. Ask an adult to help you.
- Now try swirling each balloon in a circular motion so that the object inside moves in circles.
- What can you hear?
The balloon with the smooth object will make little or no noise (you may hear it rattle a bit), but the balloon with the hexagonal nut makes a loud whirring noise.
What is going on? Sounds occur when a vibrating object causes the surrounding medium (the stuff around it, such as air particles) to vibrate. The smooth object is able to roll around inside the balloon without causing it to vibrate much, so not much noise is generated. The edges and corners of the nut cause it bounce off the inner surface of the balloon, making the balloon vibrate strongly and generating the whirring sound.
Investigate further: Spin the balloon with the nut quickly, then stop. What happens to the pitch of the noise as the nut's movement slows down?
You will hear the whirring sound drop in pitch as the vibrations slow down. The pitch of a sound depends on the frequency of the vibrations (how many vibrations occur every second). A high frequency vibration causes a high pitched sound, and a low frequency vibration causes a low pitched sound. As the nut slows, the vibrations drop in frequency, and the sound drops in pitch.
What is going on? Sounds occur when a vibrating object causes the surrounding medium (the stuff around it, such as air particles) to vibrate. The smooth object is able to roll around inside the balloon without causing it to vibrate much, so not much noise is generated. The edges and corners of the nut cause it bounce off the inner surface of the balloon, making the balloon vibrate strongly and generating the whirring sound.
Investigate further: Spin the balloon with the nut quickly, then stop. What happens to the pitch of the noise as the nut's movement slows down?
You will hear the whirring sound drop in pitch as the vibrations slow down. The pitch of a sound depends on the frequency of the vibrations (how many vibrations occur every second). A high frequency vibration causes a high pitched sound, and a low frequency vibration causes a low pitched sound. As the nut slows, the vibrations drop in frequency, and the sound drops in pitch.