What is Sound? Page 1 Page 2 Page 3 Page 4 Page 5 Page 6 Page 7 Page 8

Sound Waves.
Sound is caused by vibrations and is a form of kinetic energy.
When a ruler is twanged it vibrates and makes a noise. 
How do these vibrations travel through the air to the ears?
The air is pushed together at a high pressure (compression) and pulled apart at a lower pressure (rarefaction) by the vibration ruler.
These changes in pressure are passed through the air in the form of sound waves.
This can be expressed as a wave form on a graph with the peaks being compressions and the troughs being rarefactions.

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