Abstract: An acoustic projector device having a piston exposed to pressure balanced air and water in an acoustically ideal position thereof within a piston chamber enclosing sleeve disposed in an outer housing to which deaerating water is selectively supplied in surrounding relation to the piston chamber sleeve while in communication with one side of the piston through axial slots in the sleeve uncovered by displacement of the piston from said acoustically ideal position.

Abstract: A crescent internal gear pump achieves greatly improved sealing against cter flow of fluid and greatly reduced noise by increase of the number of teeth of each of the ring and pinion gears which form discrete volumes of pumped fluid against a crescent-shaped member or insert. Reduction of the size of the teeth on the ring and pinion gears allows an increase in the angular extent of the crescent-shaped insert in order to increase the number of discrete volumes to be increased to a minimum of nineteen for each of the ring and pinion gears. The reduction in noise is accompanied by an increase in the fundamental frequency of the remaining noise, which can be more readily attenuated by acoustic filtering and isolation. Perfecting features of the invention include shaping of the crescent-shaped member to equalize the number of discrete volumes formed by each of the ring and pinion gears and shaping the teeth of the pinion gear to equalize the volumes of the discrete volumes formed by each gear.

Abstract: Pinion and ring gears intermeshed at one location within a pump chamber are rotationally supported therein by a cylindrical bearing portion of a housing sealingly enclosing said pump chamber between side plates of the housing within which stator windings are mounted in operative alignment with permanent magnets carried in one of the gears acting as a motor rotor as a result of interaction between such magnets and magnetic fields produced by electrical input power fed to the stator windings.