Resonant underwater hydrodynamic acoustic projector

Claim 1

APPARATUS FOR GENERATING UNDERWATER SOUND AT A SELECTED FREQUENCY COMPRISING: (A) A RADIATING PISTON, (B) MEANS RECIPROCABLY SUPPORTING SAID PISTON WITH A RADIATING FACE EXPOSED FOR DELIVERING SOUND ENERGY TO THE WATER, (C) A DRIVING PISTON RIGIDLY JOINED TO SAID RADIATING PISTON, (D) A CYLINDER IN SAID SUPPORTING MEANS AND MOUNTING SAID DRIVING PISTON FOR OSCILLATORY RECIPROCATION THEREIN AND TOGETHER THEREWITH DEFINING SUBSTANTIALLY IDENTICAL CHAMBERS FOR HYDRAULIC FLUID ON OPPOSITE SIDES OF SAID DRIVING PISTON, (E) IDENTICAL HYDRAULIC FLUID OCCUPYING BOTH CHAMBERS, THE FLUID CHAMBERS HAVING DIMENSIONS AND THE HYDRAULIC FLUID IN SAID CHAMBERS HAVING RHO AND C CHARACTERISTICS, (F) WHEREBY THE FLUID IN SAID CHAMBERS AND THE EFFECTIVE RECIPROCATING MASS OF THE APPARATUS WHEN UNDER WATER AND RESONANT AT THE SELECTED FREQUENCY, (G) A CONDUIT SEALED INTO EACH OF THE CHAMBERS FOR DELIVERING FLUID-BORNE ALTERNATING PRESSURE DIFFERENTIAL TO THE CHAMBERS OF HYDRAULIC FLUID AT THE RESONANT FREQUENCY OF THE APPARTUS FOR CAUSING OSCILLATORY RECIPROCATION OF SAID DRIVING PISTON OF NEGLIGIBLE PEAKTO-PEAK AMPLITUDE COMPARED TO THE LENGTH OF EACH FLUID CHAMBER.