An Analysis of the Distribution of Measured Bubble Pulse Periods of Explosive Sources

Small explosive charges are often utilized as acoustic sources in the measurement of signal propagation in the ocean. Of particular importance when used as investigative tools is the consistency of the generated power spectrum. A measure of consistency is the degree of variation in the first bubble pulse period, defined as the interval from the onset of the initial shock wave to first bubble pulse maximum. To determine the degree of consistency that can be expected from a series of detonations, an experiment was conducted in which over 1300 charges were detonated at nominal depths of 60 and 300 feet. Using the pressure time histories, the bubble pulse periods were first determined and then analyzed from two viewpoints: first in relation to the charge specifications, and second with regard to the possible physical reasons for the shapes of the distributions. The effects of charge weight, detonation depth, temperature and wave height on the observed bubble pulse period distribution were analyzed.