What is Sound?

Sound starts when something shakes very fast. These quick little shakes are called vibrations. When a vibrating object shakes the air, the air moves in waves. When the waves reach our ears, we hear them as sound. Musical instruments send out sounds when we strike, strum, shake, scratch, pluck or blow into them. We cannot see sound waves, but they are like the circular ripples made in a pond when a stone is thrown into it. sound moves through the air in all directions at once, spreading outward as waves.