Design of a curved-face parametric projector

A transducer capable of penetrating marine sediments with multiple, rectangular beams which are broad (20°–30°) in one plane and narrow (2°–3°) in the other plane at frequencies of 10–20 kHz was desired. Transducer size constraints prohibited attaining such a beam conventionally; thus, parametric operation of a rectangular transducer was examined. A relatively high parametric source level of 190 dB re 1 μPa at 1 m was also desired, and the resulting cavitation and acoustic intensity considerations dictated a curved-face transducer design. Primary and parametric beam patterns and propagation data obtained for both a rectangular transducer and a curved-face transducer confirmed the prediction techniques being employed. Parametric beam patterns in the broad plane exhibited minor lobes with the minor-lobe structure of the curved-face transducer beam less pronounced than that experienced with the rectangular transducer. Sound pressure levels and beam patterns measured for the curved-face projector confirmed that a curved-face transducer can be operated parametrically to produce high-power, low-frequency rectangular beams.