What Is Sound?

When a police car with a loud siren rushes by, we can hear the sound of the siren. Have you ever stopped to think about exactly what sound is, though? Sounds are noises that our ears sense. The noises are created by fast-moving atoms. When atoms move from one place to another and then back again, this is called a vibration . Vibrating atoms and molecules create the sound we hear. An example is a guitar string that has been plucked. When it is plucked, the guitar string vibrates and we hear a sound. People use these vibrations to make music on the guitar. In fact sound waves are energy that we can hear!

There is a metal piece that hangs from the center of the bell. As the bell swings, this metal part strikes the bell and causes it to vibrate. We hear the vibrations as the bell continues to ring.View Larger Image

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