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What is sound?

String players in an orchestraString players in an orchestraSound is made when something vibrates (shakes). The molecules in the air (or a liquid or solid) are rapidly pushed together and pulled apart. Musical instruments make pleasing sounds. Noise is an unpleasant mix of many sounds.

The many sources of sound on a busy streetThe many sources of sound on a busy street

Birdsong, a high-pitched soundBirdsong, a high-pitched sound


Slow vibrations make low sounds. Fast vibrations make high sounds. The low-ness or high-ness of a sound is called its pitch. An example of a low-pitched sound is the rumble of distant thunder or the beat of a bass drum. Birdsong is an example of a high-pitched sound. 



Sound travels more slowly through air than through water, and more slowly through water than through steel. Sound travels more than 10 times faster through steel than through the air.

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