Development of a High Target Strength Passive Acoustic Reflector for LowFrequency Sonar Applications

摘要

Our objective was development of a broadband passive acoustic reflector with ahigh target strength to serve as a low-cost target for low frequency sonar trials and fleet exercises. The primary development goals included calibrated, stable monostatic and bistatic reflectivity and adjustable deployment depth down to 90 m. The development used both computer models and 1/4-scale physical models. Resonant air-filled cylinders were found to provide the highest TS values for a given reflector volume, the resonance occurring at ka = 0.02, at the depth of interest. Their target strength at resonance approximates that at ka 1.0 with a variation of only +/-4 dB between, yielding a broad operating range. A prototype reflector was assembled using a 16-m length of gum-rubber tubing (3.2 cm-ID). Tubing inflation was maintained by a SCUBA regulator. Test results at a depth of 90 m showed an effective target strength of 12 dB at 250 Hz. varying within +/-2 dB from 200 to 400 Hz. Subsequently, a 32-m unit was designed, built, and utilized in a sea test. This unit has enhanced bandwidth to a lower frequency of 100 Hz, achieved with four tubing sizes ranging from 3.2 to 7.6 cm ID. Passive reflector, Cylindrical reflector, Target, High target strength, Low Frequency, LFA, Low cost, Calibrated, Stable, Monostatic target strength, Bistatic target strength, Air-filled, Rubber tube.