Directionality of ground-based exploding balloons

The directionality of an explosion should be accounted for when estimating sound power. Our goal is to estimate the directionality of explosions from measurements on an arc not concentric with the origin of the explosion. To learn how to interpret such data, a test was conducted in a grass-covered field using exploding balloons. The balloons were filled with a stoichiometric mixture of oxy-acetylene and when ignited produced acoustic shock waves. The gas-filled balloons were placed in the ground in preformed “craters.” The craters were different shapes to hopefully produce different directionalities. Measurements were taken using both circular microphone arrays centered on each of the four crater locations and a single semi-circle array that was not concentric with any of the craters. The goal is to connect the two measurements by including the effective flow resistivity of the ground and determine how to interpret the directionality from data collected from the semicircle setup. This study was in preparation for a later volcano hazards workshop with buried explosives.