Measurements of Reflectivity by Explosive Signals

Abstract

Two types of reflectivity measurements were made in support of a long range acoustics propagation experiment. The objective was to obtain low frequency third octave reflection coefficients on a sloping bottom. The two types were made by (1) varying the depth of the shots at constant range and (2) varying the range of surface shots for the purpose of changing the angle of incidence. The direct and reflected arrivals were processed by a fast Fourier transform technique. The display of the arrivals and their transforms give insight to some of the reasons for the wide variability that is observed in the third octave reflection coefficients that were measured here and those reported by others. The variability in the data and the resulting uncertainty in reflection coefficients lead to the conclusion that both types of measurements yield unsatisfactory results for use in low frequency propagation models.