b. A crack and thump detection range is a live firing range. It is constructed on
terrain that slopes downward for 500 m and then upward for 200 m. The term "crack"
refers to the sound of a projectile (exceeding the speed of sound) as it passes near the
individual. The term "thump" refers to the sound caused by the expanding gases escaping
into the atmosphere when a weapon is fired (Figure 2-22).
Figure 2-22. Crack and Thump Target Detection Range.