Piezoelectric Single Crystal Applications - Development of Highly Directional Sonobuoys Using Scalar, Vector, and Dyadic Sensors

Acoustech plans a two-year effort aimed at evaluating acoustic dyadic sensors for prospective use in directional sonobuoys utilized by the U. S. Navy. The chief sonobuoys targeted in this study are the AN/SSQ-53 DIFAR, AN/SSQ-77 VLAD, and AN/SSQ-62 DICASSunits. The DIFAR and VLAD buoys are passive devices that have a bandwidth of 5 - 2400 Hz, whereas the DICASS buoy is an active device that has a bandwidth of 6.5 - 9.5 kHz. All of the sonobuoys contain an orthogonal set of vector sensors of variousdesigns (i.e., dipole hydrophones) and an omni-directional hydrophone (i.e., the so-called scalar sensor) to determine the bearing of a submerged submarine in the horizontal plane. Nevertheless, the overall intent of the project is to integrate dyadicsensors and the associated signal processing techniques into existing sonobuoy systems so that they have improved directivity and greater noise rejection without changing the aperture. Of particular interest is using scalar, vector, and dyadic sensors ina synergistic fashion to form the cardioid-squared beam pattern, which has a 3 dB beam width of 94 degrees. This represents a step gain in performance over current sonobuoys that exploit the cardioid beam pattern, which has a 3 dB beam width of 131degrees. The use of piezoelectric single crystals will play an important role to support development of small transducers that exhibit high sensitivity and low noise. A step gain in performance over current directional sonobuoys can be achieved if dyadicsensors are used in conjunction with the existing sensors they employ. It is speculated that the historically large scale production of sonobuoys (e.g., over 10,000 units per year) will drive the cost of single crystal transducers to economically viablelevels that are consistent with those associated with conventional PZT.