Just a little note:
The sonic boom is a “little” phenomenon that DOES NOT last for all the supersonic flight. It is not desirable to occur over populated areas, since it can cause (minor) material damages, but actually is nothing else than a wave conflict.
When the flight is subsonic, the air mollecules in front of the airplane start vibrating BEFORE the the airplane reaches to them, due to the sound propagation, travelling faster.
When the flight is supersonic, the nose (well, let's maybe say better “the needle” ) must cut the air mollecules that are immobile yet. Therefore there's actually a needle and not a nose, and therefore the use of special materials in order to support the high temperatures reached because of friction due to the “extra” work of cutting the air. Do not forget that, despite we do not feel it because of our low walking speed, air is something very very dense. Just try to take your hands off the window of your car when travelling at 130 Km/h (72 mph) in Europe (or 250 Km/h in Germany or in Montana daylight if you are that lucky), or even at just 55 mph (88 Km/h) in the US. Then try to imagine that speed made 1240 Km/h.
Back to the sonic boom, there is a moment, just when the speed of the plane is equal to that one of the sound, when both vibrations reach to the air mollecules at once. The sum of both vibrations creates a much bigger one which can be heard as an explosion, louder and deeper than the noise of the turbines, since the wave length is double.
Thus, a Concorde could take off from JFK, LGA or EWR east bounded, break the sonic barrier over the Atlantic, turn 180º, fly supersonic westwards absolutely silent (from earth distance, of course) over crowded land, slow down over the Pacific ocean, and land nicely and quietely at LAX.