Generation of Transient Acoustic Impulses, Using a Novel Underwater Spark Sound Source

Abstract

Investigations of an underwater, impulsive-sound-generating device are described. The device employs electric spark discharge between two volumes of sea water that are separated by a dielectric containing a small aperture. The spark occurs in and adjacent to the aperture, remote from the metal electrodes. Parametric relationships are shown for the pressure-time characteristics of the impulses radiated from single sparks as functions of circuit variables, aperture-electrode geometry variations, and static pressure. Results of input energy level variations up to 5000 J are reported, with corresponding peak-pressure outputs at 1 yd ranging up to 130 dB re 1 dyn/cm2 and pulse durations of 50 μsec. Parallel operation of more than one spark is also described, as are aperture deterioration and failure mechanisms encountered during the investigation. It is concluded that the operating characteristics of the device offers advantages within limits where precisely controlled, transient acoustic impulses of relatively low energy are desired.