A sonic boom is a thunder-like sound produced when an aircraft or other type of aerospace vehicle flies at the supersonic speed. Supersonic travel is defined as the rate at which an object travels higher than the speed of sound. In other words, supersonic speed is greater than the speed of sound.
When an aircraft flies faster than the speed of the sound(1,235 km/hr) in air, it displaces the air molecules with great force, causing the generation of sound waves. As the aircraft moves at the supersonic speed, sound waves will get emanated quickly before the previous sound wave disappears. The piling up of sound waves causes the compression of the sound waves and eventually turns into a big wave called “shock wave”.
The shock wave appears in a cone-shape and moves in all directions. Whenever, the shock wave hits the ground; a loud, startling noise is heard.
Altitude, flight path, size, shape and weight of the aircraft, and atmospheric conditions can affect the intensity of the sound boom. And, sonic booms are measured in pounds per square foot (psf) of “over-pressure”.