The world is full of waves. Amber waves of grain. Well, you get the point.
Waves are everywhere.
They learned in outlaw school that sound moves 15 times faster through steel than it does through air. We'll be catching a lot of waves this week on the program, so . . . Sound is not a thing in itself - sound is a caused by a vibration, and the movement of sound is described as a wave. Think of the kind of wave you see in a football stadium. Then, people sitting next to them take their turn standing up, waving, and so forth.