How do supersonic sources create sonic booms?

[shadowzoid]

Why do supersonic waves (when the source is faster than the wave) create sonic booms? I understand that when a source breaks the sound barrier and travels at the speed of its waves, the waves just build up at the front of the source and create a condensed sound of multiply sound waves added together, creating a sonic boom. Yet, when a source is faster than the waves, there is no buildup of waves because a new wave is created in front of the last and goes the same velocity as it so it wouldn't catch up. How do these sources create sonic booms?

http://physics.info/shock/doppler-shock-4.html
see, they don't overlap

 

[russ_watters]

I understand that when a source breaks the sound barrier and travels at the speed of its waves, the waves just build up at the front of the source and create a condensed sound of multiply sound waves added together, creating a sonic boom.

Correct.

Yet, when a source is faster than the waves, there is no buildup of waves because a new wave is created in front of the last and goes the same velocity as it so it wouldn't catch up.

Well...

http://physics.info/shock/doppler-shock-4.html
see, they don't overlap

Well then what is the dark line on the edge of that wedge-shape they form? It's still a shock wave. All that has happened between that image and this one ( http://physics.info/shock/doppler-shock-3.html ) is the angle of the two shock waves has move back/closed from perpendicular to the direction of motion. It isn't like the sound waves for a Mach 1 shock wave stay in one place: they are still propagating out away from the source along the shock wave.

 

[Matterwave]

You must consider not only the "front end" of the cone, but also the sides. For speed faster than the speed of sound, the sides of those circles still add up.

Remember, sound travels in all directions, not just forward.