Zone of silence
The zone of silence is an annular region in the vicinity of an exploded situation in which the explosion sound is not perceived.
The phenomenon is based on the refraction of sound in different warm air layers. At the transition from a colder to a warmer layer of air, a sound beam is broken away from the perpendicular. The limit angle of total reflection can be achieved at a certain height above the earth's surface ; the sound beam then runs back to the earth's surface. In the immediate vicinity of the explosion site you can hear the direct sound, outside the zone of silence the totally reflected sound. The zone of silence itself, however, is not hit by either direct or reflected sound.