Ok, I watched a TV show where they showed a test of a building designed to handle an attack like the OKC incident. There was a visible overpressure wave on the high-speed film that hit the building and cracked the glass and knocked a couple pieces of sheetrock loose (the building otherwise held up very well). They listed the speed of the shock wave as something like 4000 m/s. Since that's nearly Mach 4 and I thought speed of sound was the rate at which a pressure change equalized in the air, I found this strange. But from what I've looked up online, it seems its only true for a compression wave, not a shock wave which is denoted by its sharp change in pressure and can travel supersonic because of the sheer amount of air displaced. First, is this correct? Its been a while since a prof talked about this in dynamics (he worked for a defense contractor) and his explanation of the rarefraction from a detonation causing more damage than the compression wave because of the flying debris didn't sit well with my idealistic thinking at the time.... Second, at what rate of change does this transition occur from compression wave to shock wave?