Sound

Sound can also mean a body of water, like a bay or channel.

Sound is caused by sound waves. It can be heard when goes through a medium to the ear. All sounds are made by vibrations of molecules. For example, when a person hits a drum or a cymbal the object vibrates. These vibrations make air molecules move. Sound waves move away from where they came from. When the vibrating air molecules reach our ears, the eardrum vibrates, too. The bones of the ear vibrate in the way the object that started the sound wave vibrates.

There are three different mediums. They are solids, liquids and gas. Sound travels fastest through solids because the particles in a solid are closer together than they are in gases and liquids.

These vibrations let you hear different things. Even music is vibrations. Irregular vibrations are noise. People can make very complex sounds. We use them for speech.

Sound waves are longitudinal waves with two parts: compression and rarefaction. Compression is the part of the sound waves where the air molecules are pushed (compressed) together. Rarefaction is the part of the waves where the molecules are far away from each other. Sound waves are a sequence of compression and rarefaction.