ASA 125th Meeting Ottawa 1993 May

4aUW12. Further comments on beamforming with acoustic measurements at a single point in the ocean.

G. L. D'Spain

W. S. Hodgkiss

Marine Phys. Lab., Scripps Inst. of Oceanogr., San Diego, CA 92152-6400

Previously, the idea of using multi-component acoustic measurements at a single point in the ocean, rather than spatially distributed measurements of pressure, to obtain information on the spatial dependence of the ocean acoustic field was introduced [G. L. D'Spain and W. S. Hodgkiss, J. Acoust. Soc. Am. 91, 2364(A) (1992)]. The basis for this single-point measurement approach is a Taylor series expansion of the pressure field. The purpose of this presentation is to further extend these ideas, including the use of adaptive time-varying array weights to perform correlated noise cancellation and the application of Capon's minimum variance method to measurements in a second order Taylor series expansion. In addition, ways of processing the data collected by a line array of multicomponent sensors in order to eliminate spatial aliasing when the interelement spacing is somewhat greater than the half-wavelength criterion will be presented. Finally, the application of high-resolution beamforming techniques with actual multi-component (hydrophone and geophone) data for the determination of the azimuthal directionality of the underwater sound field below 5 Hz in several experiments will be discussed. [Work supported by ONR and ONT.]