AN INVESTIGATION OF THE ACOUSTIC EMISSIONS FROM A BUBBLE PLUME

This letter presents some preliminary results of an experimental study of the underwater sound field emitted by a bubble plume. The densely populated bubble plumes were generated by dropping a fixed volume of water, held in a cylindrical container, onto a still water surface. The characteristics of plumes were varied by changing the container volume and height above the surface. Acoustic emissions from these plumes appear to depend on the volume of the injected water, with the emitted frequency band decreasing with increasing plume volume. In addition, large-amplitude, low-frequency emissions correlate well with the observed detachment of "substructures" within the plume. The frequencies of the acoustic signals associated with the formation of these structures range as low as a few tens of Hertz.