# How do supersonic sources create sonic booms?

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 [Broken]
see, they dont overlap

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russ_watters
Mentor
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 [Broken]
see, they dont 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 [Broken] ) 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.

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Matterwave