Almost everyone is aware that sound is nothing but a wave and a sound wave is the pattern of disturbance caused by the movement of energy traveling through a medium (such as air, water, or any other liquid or solid matter) as it propagates away from the source of the sound.
The source of wave is some object that causes a vibration, such as a ringing telephone, or a person's vocal chords. The vibration disturbs the particles in the surrounding medium; those particles disturb those next to them, and so on. The pattern of the disturbance creates outward movement in a wave pattern, like waves of seawater on the ocean. The wave carries the sound energy through the medium, usually in all directions and less intensely as it moves farther from the source.

This sound wave can take beautiful patterns when the frequencies are controlled and varied as in different frequencies they take part in constructive or destructive interferences.

Just look at this video, which features fascinating patterns of sound wave with a medium of salt.

http://www.youtube.com/watch?v=s9GBf8y0lY0