iirc there should be a sonic boom for every multiple of the sound barrier iirc there should be a sonic boom for every multiple of the sound barrierGeez, I don't think so! Why would there be? The angle of the shock wave to the flight path just gets steeper as the Mach number increases. I believe at high Mach numbers, there are qualitatively new effects, but this is due to intensification of the shock front.
The double boom from the Space Shuttle was due to two separate shock waves orginating from the nose and the tail, I think.