# Sonic Booms

How do Sonic Booms work? Y’know, when an aircraft breaks the sound barrier and produces an audible explosion. I assume it must have something to do with sound waves no longer being able to travel forward from the travelling craft and bursting back past the nose of the craft. Is the sound influenced by the shape of the aircrafts nose?

But what puzzles me even more is that (unless I’m misinformed about this) you get repeated booms every time the aircraft goes through different stages. i.e. MACH1, MACH2 etc. How does that work, cos I can think of no logic explanation for this latter phenomena?

Emphasis mine
Complete text and a pretty cool picture found at:

http://www.rlcnet.com/soap/soundbarrier.htm

Once again it should be emphasized that the “boom” is the sound heard as the shock wave created by the supersonic aircraft passes by. You don’t hear it in the aircraft since the shock wave is traveling with the plane. There is no audible clue onboard the aircraft to tell you that you have exceeded the sound “barrier”.

So, for the OP, the shape of the nose of the aircraft is not important in this regard. It does significantly affect drag and other flight parameters but not the presence or absence of a sonic boom. Also, there is only one sound barrier – the phenomenon doesn’t repeat at successive Mach numbers.

There are actually two sounds. The first when the plane approaches and the second when it leaves.

A sonic boom occurs anytime an object is exceeding the speed of sound, not just at the instant that it crosses the Mach 1.0 level. Don’t confuse breaking the sound “barrier” with the boom.

Think of the boom as the equivalent of the wake that comes out from a boat. As long as the boat is moving faster than the speed of a wave in water, then you’ll get the wake. It will hit you on the shore sometime after the boat passes in front of you. The wake will be shaped like two sides of a triangle (or a cone for a jet’s 3-D sonic wake), and as the boat goes faster, the point angle will get sharper. A bow wake is really just a two-dimensional sonic boom.