A theoretical treatment of the long range propagation of impulsive signals under strongly ducted nocturnal conditions

On clear nights, over flat land, a sound duct develops in which sound can carry to great distances. As is the case with all ducted propagation, there is strong dispersion so that a broadband signal undergoes severe distortion as it propagates. The signal received at long ranges from an impulsive source is a wave train, of much greater duration than the initial impulse, consisting of a series of arrivals. The long range ground to ground propagation of an impulsive signal in a typical nocturnal duct is studied and the natures of the various arrivals are explained. A direct connection is drawn between the meteorological and ground conditions and the structure of the propagated signal.