Acoustic signatures from deep water implosions of spherical cavities

Abstract

Hollow glass spheres of various sizes have been preweakened to implode at ocean depths of approximately 3 km and sunk using chain weight. Acoustic signals generated from the implosion of these spheres have been analyzed. Pressure signatures, energy-density spectra, and total acoustic energy in the frequency band 96–5000 Hz are presented. The signatures of all the implosions have many features in common. Basically each consists of a low flat negative-pressure pulse followed by a sharp positive-pressure spike of roughly 0.2-msec duration. The efficiency of the conversion of available potential energy to radiated acoustic energy is approximately 18%. Total radiated acoustic energy for spheres of 43.2-cm diameter imploding at a 3-km depth is about 53 dB re 1 J. Preweakened glass spheres show promise as a tool in the study of the sedimentary structure of the ocean bottom due to the impulsive character of the signal that is radiated upon implosion. Subject Classification: [43]30.50, [43]30.60, [43]30.70.