All sounds begin with vibrations. When these vibrartions in an object are set up, such as when a drum or cymbal is hit, the air molecules in the immediate area also begin to vibrate. This vibration causes adjacent molecules to move so that the air molecules are effectively pushed together and pulled apart. This pushing and pulling is called compression and rarefaction. This vibrating air causes our eardrums to vibrate, in turn a signal is sent to our barin which interprets the sound. But sound can also travel not just through a gas like air, but also through solids and liquids (see states of matter). Sound actually travels faster and better through solids and liquids than it does through a gas because of the way the molecules are arranged. In solids and liquids, the molecules are more tightly packed than in gases which allows the vibrartions to take place more easily
It is possible to vary both the pitch and volume of a sound.Follow thes links to find out more about these.
