A sonic boom occurs when an object travels faster than the speed of sound. The boom itself is caused by an object, such as a supersonic airplane, traveling faster than the sound waves themselves can travel. The sound waves pile up on one another, creating a shock wave that travels through the atmosphere, resulting in a “boom” when it strikes a person’s ears. A sonic boom is not a momentary event that occurs as the plane breaks the sound barrier; rather, it is a continuous sound caused by a plane as it travels at such a speed, but the shock wave travels with the plane, so we hear it only when the plane is in one location.

All objects that exceed the speed of sound create sonic booms. For example, missiles and bullets, which travel faster than the sound barrier, produce sonic booms as they move through the atmosphere. The shockwave created by an F-15 fighter plane, for instance, is visible.