A sonic boom is a powerful shockwave generated when an object, such as a rocket or supersonic aircraft, travels faster than the speed of sound. This phenomenon occurs because the object compresses air in front of it, creating a wave of pressure that propagates outward at high speed. From the perspective of an observer, a sonic boom is experienced as a sudden and very intense burst of sound that typically lasts under a second. The image below shows the point at which the observer on the ground experiences the boom as the sonic boom cone edge or “carpet” passes them.
In the United States, supersonic commercial flights over land were banned in 1973. This law is still in effect today, but there are certain situations that these laws do not cover (including certain supersonic test areas and rocket launches).
It is important to distinguish a sonic boom from the engine noise—often referred to as a “rumble”—that accompanies rocket launches or the operation of supersonic aircraft. While the rumble is a lower-intensity sound that can last for around a minute, the sonic boom is a much shorter-lived but highly intense sound event. Understanding this distinction helps us better appreciate the nature and impact of these phenomena on communities and the environment.
In the video below, you can hear the intense sonic boom of a returning Falcon 9 booster followed by the continuous rumble of the engine to slow its descent before landing. Note that it isn’t possible for standard audio equipment (or smartphones) to accurately record, measure or playback a sonic boom as the sound frequencies are in the 0.1–100 hertz frequency range, typcally referred to as “subsonic”.