Measurements of underwater sound intensity vector

Localization of underwater sound sources and characterization of ambient noise fields can be achieved through measurement of the sound intensity vector. To evaluate this concept, a passive hydrophone array called SIRA (Sound Intensity Receiver Array) has been developed for measurement of underwater sound intensity in the frequency range 100 to 6000 Hz. The array is composed of three pairs of omnidirectional hydrophones with the pairs aligned along orthogonal axes. The intensity is the time average of the product of instantaneous acoustic pressure and particle velocity. The instantaneous pressure is the average of the pressures measured by a hydrophone pair and the velocity is derived from the pressure gradient. Each hydrophone pair provides one of the components of the three dimensional intensity vector. Preliminary intensity measurements made at the Defence Research Establishment Atlantic (DREA) calibration barge facility are presented. The high angular resolution of the intensity measurements is demonstrated as well as the effect of ambient noise on the magnitude of the intensity.