Comparative beamforming studies employing acoustic vector sensor data

Abstract

Data obtained from a vector-sensor line array (VSLA), while deployed vertically at Lake Pend Oreille during calibration, are examined in the context of propagation phenomena. Both broadband (FM sweep) and cw signals are analyzed. Only linear plane-wave beamforming is considered, based on well-established array processing techniques for vector sensors [Cray and Nuttall, J. Acoust. Soc. Am. 110, 324 (2001)]. Normalization is addressed, as is the determination of the vertical plane of propagation for proper steering of the vector components. Results show that the vector sensor array can be properly scaled and steered using a strong, single, cw source. Peak-to-sidelobe improvements of several dB were observed using vector beamforming rather than pressure-only beamforming. Arrival direction resolution using cardioid null is also presented. The vertical configuration allowed testing of predicted multipath interference behavior. As expected, arrival angle determinations with a single vector sensor is possible with the broadband signal. The difficulty of similarly resolving multipath arrival angles with one vector sensor and a single cw tone is shown. An array of vector sensors will resolve these angles. [Work completed with the support of Michael Traweek, Thomas Curtin, and Ellen Livingston, all from the Office of Naval Research, and by Daniel Deitz of NAVSEA-PMS403.]

Numerical Studies of Acoustic Particle Velocity and Acoustic Variability with a SSF/PE Model

“…This data was then used to test processing routines for plane-wave beamforming and processing of acoustic intensity. [3] Numerical investigations of matched-field processing with vector sensor data was also considered. [4] Once the routines were successfully tested, measured data from a NUWC vector sensor line array (VSLA) was processed.…”

“…These results are consistent with previous predictions of multipath influences and degradation of vector sensor array performance. [3] However, it is important to recognize that these degradations are due, in part, to the simplifying assumptions inherent in standard, linear, plane-wave processing. More sophisticated processing techniques that do not make such assumptions and attempt to account for the multipath structure may be more robust.…”