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Sound is all around us, but what is sound? Sound is a type of energy made by vibrations. When any object vibrates, it causes movement in the air particles. These particles bump into the particles close to them, which makes them vibrate too causing them to bump into more air particles. This movement, called sound waves, keeps going until they run out of energy. If your ear is within range of the vibrations, you hear the sound. Picture a stone thrown into a still body of water. The rings of waves expand indefinitely. The same is true with sound. Irregular repeating sound waves create noise, while regular repeating waves produce musical notes. When the vibrations are fast, you hear a high note. When the vibrations are slow, it creates a low note. The sound waves in the diagram show the different frequencies for high and low notes. || **High frequency notes** ||
 * **Low frequency notes**

Discuss these questions with your partner.
 * 1) Can sound travel under the water?
 * 2) Is there sound on the moon?
 * 3) What is the speed of Sound?

Click here for answers.