"Sound" is due to something moving slower than, well, the speed of sound.  "Shock waves" travel faster than that.

Really Big explosions can create shock waves that move faster than sound for a long way, but your firecracker examples are just the usual form of sound-based noise.

The _sound_ of the explosion is propagated by the motion of the atoms due to their thermal energy.  One way to see this:  Far from the firecracker, the energy of the explosion has not increased the energy of the air molecules at all:  their mechanism for transporting sound energy isn't about the firecracker at all.