I saw this trailer for the new movie Ironman, which comes out later this year. I should probably add that I have nothing to do with the movie.
If you skip to 2:20 (the last 9 seconds), Downey goes supersonic, creating a shock wave which then dissipates as I assume he gains velocity beyond Mach 1.
Wouldn’t a second shock wave, known as a bow wave form at the base of his body? Would we hear anything after the sonic boom? two booms?
Here’s a well-done page where I found some information.
Video here gives good overview.