Triplane reflector with controlled frequency-dependent target strength

Claim 1

A TRIPLANE REFLECTOR HAVING A PREDETERMINED CUT-OFF FREQUENCY ENABLING THE REFLECTOR TO TRANSMIT SOUND WAVES OF A WAVELENGTH SHORTER THAN CUT-OFF AND TO REFLECT SOUND WAVES OF A WAVELENGTH GREATER THAN CUT-OFF, SAID REFLECTOR BEING ADAPTED TO SERVE AS AN ACOUSTIC TARGET IN A FLUID MEDIUM, COMPRISING A PLURALITY OF SUBSTANTIALLY ACOUSTICALLY-INOPERATIVE INTERESTING PERFORATED PLANAR FRAMEWORK MEMBERS MOUNTED TOGETHER AT RESPECTIVE RIGHT ANGLES TO ONE ANOTHER TO DEFINE A TRIPLANE FRAMEWORK STRUCTURE, A PLURALITY OF FLEXIBLE ACOUSTICALLY-OPERATIVE PERFORATED PLANAR MEMBERS EACH OF WHICH IS SUPERIMPOSED IN MATING REGISTRY WITH ONE OF SAID FRAMEWORK MEMBERS AND CONNECTED THERETO, SAID ACOUSTICALLY-OPERATIVE PLANAR MEMBERS BEING COMPOSED OF A MATERIAL HAVING A SPECIFIC ACOUSTIC IMPEDANCE LOWER THAN THE SPECIFIC ACOUSTIC IMPEDANCE OF THE FLUID MEDIUM IN WHICH SAID TRIPLANE REFLECTOR IS TO SERVE AS A TARGET, THE DIAMETERS OF THE PERFORATIONS IN EACH OF SAID PERFORATED PLANAR FRAMEWORK MEMBERS BEING CONSIDERABLY IN EXCESS OF THE THICKNESS OF EACH RESPECTIVE PLANAR FRAMEWORK MEMBER AND THE DIAMETERS OF THE PERFORATIONS IN SAID FLEXIBLE ACOUSTICALLY-OPERATIVE PLANAR MEMBERS BEING DETERMINED IN ACCORDANCE WITH SAID PREDETERMINED CUT-OFF FREQUENCY, THE MATERIAL OF SAID PERFORATED ACOUSTICALLY-INOPERTIVE PLANAR FRAMEWORK MEMBERS BEING ALUMINUM, THE MATERIAL OF SAID FLEXIBLE ACOUSTICALLY-OPERATIVE PERFORATED PLANAR MEMBERS BEING CORKNEOPRENE, AND THE DIAMETER D OF SAID PERFORATIONS BEING DETERMINED BY THE FORMULA D=113/FCO WHEREIN FCO IS THE CUT-OFF FREQUENCY AND D IS THE DIAMETER IN CENTIMETERS.