What is the difference between a shock wave and a sound wave?

That's how a shock wave develops from sound waves that pile up. Physics in the shock front can become quite complicated. When you have a very strong supersonic shock with a large pressure differential, entropy can also be created across the shock discontinuity. read more

A sound wave is a limiting case of a shock wave, in which the pressure discontinuity across the shock tends to zero. The disturbances are effectively assumed to be infinitesimal in the treatment of sound waves, and there is no change of entropy during the process. read more

Sound waves are generated when something alternately compresses and decompresses air. If the molecules are pushed faster than the sound wave can propagate then the wave is a shock wave. read more

One thing that distinguishes a shock wave from a normal sound wave is that it travels faster than what we typically call sound. This is because its intensity is such that it significantly heats the gas media adiabatically. The speed of "sound" is an increasing function of temperature. read more