Sonic boom is a loud noise caused by an object--usually an airplane--flying at a supersonic speed. To a person on the ground, it may sound like a clap of thunder. The noise results from a shock wave produced by the plane. A shock wave is a pressure disturbance that builds up around a plane flying at a supersonic speed. It results from a change in the air-flow pattern around the plane's leading edges. Sonic booms cannot hurt people, but they may damage plaster walls and break windows.