Ducted propagation in the atmosphere, from audible sound to infrasound

Earth's atmosphere supports complicated and highly variable winds and temperature gradients. Temperature inversions and wind jets provide ducts in which sound can propagate efficiently to great distances from the source. Due to the intrinsic variability of the atmospheric winds, these sound ducts are also quite variable, both temporally and spatially. Further, the direction of the atmospheric winds can change dramatically with increasing altitude so that the behavior of the propagated field can become quite complex as the range from the source increases. Despite this, some systematic behavior has been observed in long range sound propagation. An overview will be presented, with an emphasis on the systematic behavior. The current state of our understanding of the sources and consequences of the atmosphere's variability will be discussed.