Effects of Frequency, Temporal, and Spatial Averaging on Image Interference
DAVID TAYLOR RESEARCH CENTER BETHESDA MD SHIP ACOUSTICS DEPT
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This report describes a significant phenomenon affecting the propagation of underwater sound at ranges less than 1000 yards, the image interference or Lloyd-mirror effect. Previous models for the effect do not adequately take into account the effects of frequency averaging and spatial averaging due to sea surface roughness and finite source size. These refinements on the basic theory are developed here. Also a clarification of the meaning of the surface reflection coefficient is given for the case of omnidirectional sources and receivers -- the situation that prevails in ship radiated-noise trials.