A High Resolution, Low Frequency Parametric System for Oceanographic Research

摘要

The development and application of a parametric acoustic array system is described. Key features include a 720 element primary projector measuring 2.3 m in diameter, with a fundamental resonance in the 11-16 kHz band. Eighty kilowatts of primary pulse power are applied to this array to develop difference frequency radiations in the 500 Hz to 5 kHz band. Half-power beamwidths of the primary and difference frequency radiations are on the order of 2.5 deg. An array of 30 low frequency elements is interleaved in the primary array for reception of the difference frequency echoes as well as for transmission of linear signals in this band. The system has a capability for alternate parametric and linear transmission to enable near simultaneous acquisition of parametric and linear data. A capability for sequentially stepped center frequencies is also provided for near simultaneous frequency response measurements. Shaped pulse (i.e., gaussian, box-car, etc.) as well as variable bandwidth FM pulse operaton is also provided. Mechanical features include mounting on an offshore platform with continuously variable transducer tilt, train, and depth positioning, as well as VDS towing in a spherical fish with rope fairings. Application of the system to environmental acoustics research is also described. (Author)