Over the weekend, an F-16 fighter jet was sent to investigate a small private plane that wasn’t communicating with air traffic controllers. It then changed course, heading toward Washington, D.C., which is restricted airspace.
The F-16 was in a hurry, traveling fast enough to create a sonic boom. The
explosion-like sound was heard throughout D.C. and even in Baltimore, Maryland. Buildings even shook a bit.
How did a sonic boom happen in Washington, D.C.?
To explain a sonic boom, look at a boat.
As a slow-moving boat moves through the water, it creates a series of waves that move out
from the boat. These waves have plenty of room to rise and gently subside.
But if a boat is moving faster, these waves don’t have time to get out of the way of the
next wave, so instead of many small waves, it creates a large one. It’s called a wake.
Another example is the crack of a whip. The handle is thicker and has more mass. The whip tapers off to a very thin tip, called the “crack.” As the speed moves down the thinning whip, it speeds up and breaks the sound barrier. This gives us a crack that is a “mini” sonic boom.
With that in mind, let’s get back up into the air.
When a plane is traveling less than roughly 760 mph, the sound waves push out with room to
rise and fall. That’s why when you hear a plane, the noise isn’t constant but comes and goes
in a pattern. Those are the waves.
How fast does a jet need to travel to create a sonic boom?
It depends on atmospheric conditions and temperature, but generally, when a jet gets above 761 mph, the sound waves don’t have enough room or time to “get out of the way.” So for a moment, there is silence, then we hear the large wave, or the sonic boom.
It’s actually illegal to fly supersonic, or MACH 1, over the mainland of the United States. However, this event was cleared by the FAA.
How far away can you hear the sound of a sonic boom?
How far can a sonic boom be heard? It can be heard around one mile for every 1,000 feet of altitude. So an aircraft flying supersonic at 30,000 feet will spread a lateral boom about 30 miles.