Advanced Binaural Sonar Display for Collision Avoidance: Applying Spatial Vernier Beamforming to the Wide Aperture Array

Operating in a dangerously sensor-limited closed environment, submarine sonar operators are plagued by primitive sensory interfaces inherited from earlier hardware designs. The inefficient match to the operator's perceptual capability is exacerbated as submarines increasingly operate in the littoral where, at now reduced ranges from quieter threat targets, detection requires immediate action for crew safety. Present use of the sonar operator's auditory ability ignores the superior acuity of the mammalian binaural system. In humans, this system is sensitive to minute instantaneous differences in phase, intensity and time of arrival between its two channels. This research developed, and perceptually tested, a binaural auditory display that optimized the essential noise correlation between a pair of formed listening beams. To generate the necessary perceptual characteristics for the binaural display, a breakthrough audio beamforming process formed beams from a hull mounted wide-aperture hydrophone array (WAA) which were focused at two different distances but in the same direction. This unique processing, named Spatial Vernier Beamforming (SVBF), maintained the essential high noise correlation between the pair of formed directional beams. Once appropriate beamforming was proven feasible, laboratory testing was undertaken to quantify perceptual performance. A representative sample of 15 sonar contacts were beamform processed, stored as wavefiles and systematically presented to a group of 18 highly experienced sonar operators. Results show a highly significant 8.6 dB detection improvement over the current single beam display. This improvement represents the ability to acoustically detect targets at more than twice the distance currently achieved. The original document contains color images.