Experiments with a large aperture parametric acoustic receiving array

The Parametric Acoustic Receiving Array (PARRAY) is a receiving array which achieves the directional reception characteristics of a continuous end-fire line array by the use of only two transducers (pump and hydrophone). The PARRAY synthesizes a virtual receiving array with acoustic aperture equal to the pump-hydrophone separation. Since the PARRAY is a system involving a number of active components which are required to process signals with wide dynamic ranges, the implementation of a practical and useful PARRAY involves meeting stringent system self-noise requirements. A PARRAY with 340 m pump-hydrophone separation operating over the 35 to 800 Hz range has been tested in a fresh water lake, with results showing that the self-noise level of the PARRAY is below the ambient noise level in this environment. A description of the PARRAY implementation is presented with the test results.