Experimental measurements with a large aperture PARRAY

A parametric acoustic receiving array (PARRAY) is characterized as a continuous, virtual end-fire array of length equal to the separation between the pump and hydrophone. Therefore, the directivity index of a PARRAY is approximately equal to 10 log (4 L/λ) where L is the pump-hydrophone separation and λ is the wavelength of the acoustic signal. A PARRAY with a pump-hydrophone separation of 340 m has been installed in 45 m of water at the Lake Travis Test Station of Applied Research Laboratories, The University of Texas at Austin. Measurements over the frequency range from 40 to 800 Hz show spatial processing gains approximating the directivity index of the PARRAY. The geometry of the experiment will be described and data obtained with the 340 m PARRAY will be presented and discussed. [This research was supported by the Advanced Research Projects Agency of the Department of Defense and was monitored by the Naval Electronic Systems Command under Contract N00039-76-C-0231.]