[Physics] Is a sonic boom a one-time bang or a continuous noise

Question

Is a sonic boom a one-time bang, caused when an object initially goes supersonic, or is it a continuous noise emitted by the object as it's travelling?

To be more specific, will an aircraft which is continuously accelerating cause a boom only over the point where it first transitions to supersonic, or does it cause a 'boom' to be heard over the whole length of it's supersonic journey by all of the observers along it's route (the same way that a fast boat will create a bow wave which follows it wherever it goes)?

Answer 1

I've received an answer/explanation from Jim Wild at Lancaster University. I'll add it here in case anyone's interested. Full credit to him :)

Jim Wild: But basically, no it's not just a single one-time bang. The pressure wave (which we perceive as a boom) is generated continuously as long as the aircraft is moving supersonically. This is why supersonic flights are usually prohibited over land - there isn't just one bang, it would "follow" the aircraft and be heard by lots of people!

Back when Concorde was flying, had you placed a chain of listening posts across the Atlantic, you would have been able to detect the aircraft moving across the ocean as it overflew each station, even if it only "broke" (i.e. accelerated through) the barrier once just after leaving the coast.

See: http://www.bbc.co.uk/news/science-environment-17701155