To calculate the distance from a stationary visible object using the speed of sound when dealing with a supersonic blast wave from that object, how would one proceed? Is the standard 340m/s good enough reference? How is the velocity reduction over time and distance? Does all the variables (temperature, elevation and such) have a notable impact on velocity reduction? For these examples lets say sea level at 20C. Example 1: Looking at a large amount of high exploive, TNT, going off from far away, say 5km. How to calculate distance? Example 2: This is what triggerd me into reserching this. A volcano eruption caused a shock wave that traveles for 13sec from point of origin to the viewer. At the viewer it still sound like the wave was supersonic (through a video).