ASA 124th Meeting New Orleans 1992 October

4aEA10. Conformal baffled line array for the AUTEC ocean haul down facility.

Richard K. Menoche

Gerald M. Santos

Naval Undersea Warfare Ctr., Code 382, Newport, RI 02841

Peter J. Stein

Atlantic Appl. Res. Corp., 4 ``A'' Street, Burlington, MA 01803

The radiated noise goals for various underwater vehicles are becoming more stringent. As these goals are approached, novel acoustic test and evaluation schemes will be required to overcome ambient noise limitations and confirm performance. Customized directive arrays will be required in order to make the measurements. Large multielement volumetric arrays will be cost prohibitive. Here, a unique baffled vertical line array deployed at the AUTEC ocean haul down facility is described. This device was designed to overcome shrimp noise from a nearby reef and make acoustic measurement of buoyant test vehicles and weapons under shallow-water conditions. This array meets the following specialized criteria: (1) very high backside rejection to shield the array from shrimp noise, (2) very wide (120(degrees)) frontside horizontal beam pattern to ensure capturing the vehicle as it passes the array, (3) beam patterns stable to within 1 dB over the beamwidth for accurate measurements, and (4) the ability to discriminate against surface noise. Diffraction problems from the edge of the baffle were solved by randomizing the edges thereby creating what is called ``diffraction wings.'' Plate vibration problems were solved by constructing a baffle with blocks welded to the back of a relatively thin plate (thereby having mass with no stiffness) and the addition of damping treatment. Receiver standoff problems were solved by the use of conformal PVDF sensors.