Abstract: A marine seismic vibrator includes a housing having first and second housing portions defining an internal chamber therebetween. A hydraulic cylinder or other energizing device is connected between the first and second housing portions. The first and second housing portions are maintained in a spaced apart, non-contacting relationship. Relative motion between the first and second housing portions is provided by the hydraulic cylinder in order to generate acoustic waves in a surrounding body of water. An annular flexible seal construction is connected between the first and second housing portions for isolating the internal chamber from the surrounding body of water. This seal construction includes first and second flexible web portions sealingly connected to the first and second housing portions. A rigid hoop is connected between the first and second web portions for supporting the seal against pressure differentials between the internal chamber and the surrounding body of water.

Abstract: An underwater speaker system having a pressure equalization system enabling the speaker to operate in its intended fashion over a wide range of water depths, e.g. from two feet up to sixty feet. Water pressure is applied to a diaphragm that forms one wall of a variable volume an internal face of a speaker membrane. Pressures are equalized on opposite faces of the membrane to enhance speaker performance.

Abstract: A tubular acoustic projector for underwater use consists of a ceramic, piezo-electric transducer (21A, 21B) contained in a coaxial, electrically-conductive cylindrical housing (10) whose side wall (11) is thin enough to vibrate with the transducers (21A, 21B). The side wall (11) maintains the transducer under a radial compressive pre-load so as to avoid ceramic failure due to tensile stress. The side wall is sufficiently thermally conductive to dissipate the heat generated in the transducer, in use, to prevent failure of the transducer under the effects of heat. Electrical isolation of the inner and outer surfaces of the transducer is achieved by filling the housing with an insulating liquid.

Abstract: A seismic energy source provides a bias pressure and oscillating pressure force on a piston mounted transversely to the major axis of the well bore and in pressure contact with the wall of the well bore. A seismographic energy wave is generated in the surrounding earth by oscillating the pressure of the piston against the well wall. This apparatus uses the pressure of ambient fluid in the well bore to reduce the power required to provide pressure contact and to oscillate the piston against the wall.

Abstract: Omnidirectional, wide pass band, elastic wave transducer comprising a rigid magnetostrictive diaphragm, each surface element of the diaphragm constituting a unidirectional elastic wave transducer in its normal direction, and an electric control means provided with two electric terminals for producing in the vicinity of the diaphragm a homogeneous magnetic field in keeping with an electric signal applied to the terminals of the control means or for supplying an electric signal in keeping with the variation of the magnetic field in the diaphragm as a function of an elastic wave received. The diaphragm is preferably a closed surface of revolution.Application in submarine transmission (hydrophone) and in high fidelity sound reproduction (loudspeaker, microphone) with a very wide pass band.

Abstract: A wide-range audio frequency underwater transducer is designed to make use of a massive small diameter vibratile piston driven by electromagnetic oscillatory forces to transmit omnidirectional uniform sound pressure level over the frequency range 100 Hz to 5 kHz. The rugged transducer design is adapted for low-cost mass production and can be used as a highly reliable expendable reference standard of source level for the calibration of in-situ stationary or moving sonar receiving systems. The magnitude of the source level can be accurately controlled by the magnitude of the electrical current supplied to the electrical winding over the entire frequency range of operation. A pressure equalization system is included in the design that permits use of the transducer at any depth down to 500 feet.

Abstract: A Tonpilz transducer having head and tail masses with an interposed active transducer section. The transducer unit is positioned within a housing which has a shoulder portion upon which rests a snubber member which extends to a position just behind the head mass. The transducer is supported from the head mass by means of a thin fiberglass tube which extends from the rear of the head mass and engages a flange portion of the snubber member in the vicinity of the housing shoulder. The housing has a waterproof covering as does the head member with the covering of the head member being secured to the covering by means of a removable strap such that the transducer assembly may be disassembled for repair.

Abstract: A mechanism for compensating an underwater transducer for the ambient hydrostatic pressure. The transducer housing includes a quantity of liquid which may be vaporized in the housing volume. The relative volumes of vapor and liquid depend on the temperature, pressure and type of liquid used. A small heater in the liquid increases the temperature of the liquid so that the pressure of the vapor increases and counteracts the increase in hydrostatic pressure at greater depths. The liquid chosen should have a high critical pressure relative to the operating pressure of the transducer.

Abstract: A ruggedized depth transducer for measuring ambient hydrostatic pressure adjacent an acoustic source wherein the transducer includes a housing having a depth sensor mounted therein. The housing further includes a bore for placing the depth sensor in fluid communication with the ambient pressure. Mounted within the housing bore are a series of mechanical filters for attenuating high-intensity pressure spikes generated by the acoustic source from damaging the depth sensor contained within the housing. The mechanical filters allow gradual changes in ambient pressure to pass into the bore and influence the depth sensor.

Abstract: A bladder shaped to conform to the form of the sonar transducer housing of a torpedo in which it is located compensates for volume changes because of temperature changes of the oil which fills the transducer housing. The bladder also compensates for the change in water pressure produced by the depth at which the torpedo is operating. The bladder is sufficiently stiff so that it maintains a predetermined shape substantially midway between its fully extended and fully compressed position during the time that the housing is air evacuated and then filled with oil at near atmospheric pressure. The bladder is thus capable of expanding or contracting to accommodate changes in the volume of the contained oil as the temperature of the oil changes. The bladder is preferably made of a material without substantial spring force or stretch.

Abstract: A microbending fiber optic acoustic sensor. A point hydrophone according to a first preferred embodiment of the present Invention includes two opposed pistons which are subjected to an acoustic pressure wave. In response to the pressure wave, the opposed pistons push a pair of deformer plates against an optical fiber to deform the fiber thereby intensity modulating an optical signal passing through the fiber. An extended hydrophone according to a second preferred embodiment of the present Invention includes an optical fiber wound in a helical groove formed in a cylindrical surface. A plurality of parallel axial slots are located in a spaced-apart relationship to each other at positions about the cylindrical surface and are oriented in parallel with the axis of the cylindrical surface. Each axial slot intersects with the helical groove at a plurality of locations and has a depth greater than the depth of the groove.

Abstract: An underwater transducer in which a ring of piezoelectric ceramic elements vibrates radially in response to an applied voltage. Spacer elements formed of steel are placed between pairs of ceramic elements and used to couple the ring movement to convex diaphragms. Each diaphragm is formed with radially extending fingers, which attach to the spacer elements. A water bladder assembly within the transducer forms a passive internal pressure compensation system. Preferably, the water bladder assembly is attached to the ring in a manner that mechanically decouples the bladder assembly from the ring.

Abstract: A hydroacoustic transducer provides an improved hemispherical radiation pern throughout a wide range of operating depths. A can-shaped transducer is nestled in the inside of a hat-shaped array of hollow spheres. Resiliently mounting the spheres with respect to each other and a hat-shaped shell holds the array away from the surface of the transducer and layering the hollow spheres assures the hemispherical pattern. Fashioning the spheres from hemispherical shells of aluminum and bonding them together makes the array insensitive to greater or lesser hydrostatic pressures and potting the array in polyurethane presents a more rugged structure capable of withstanding the routine abuses of the ocean environment.

Abstract: The invention relates to hydrophones which require liquid backing of the sensing plate, and more particularly, to compliance enhancing means for use in such hydrophones. In a practical embodiment, in which a compliant sensing plate in the form of a thin diaphragm is employed, liquid backing of the sensing plate is provided to balance the hydrostatic pressure across the sensing plate. To increase the compliance of the hydrophone, reduced by the presence of the backing oil, and to do so in a linear manner, a bellows is introduced into the backing chamber having the desired compliance and pressure rating. The invention is applicable to hydrophones having either compliant or stiff sensing plates. An improvement in hydrophone linearity and sensitivity is obtainable over a significant range of hydrostatic pressures.

Abstract: An optical grating hydrophone employs a dual grating construction and two pairs of optical fibers to provide a reliable output signal without the need for mechanically adjusting the system bias. A bias compensation circuit selects the output signal to be received based upon the output signals from the two optical cable pairs.

Abstract: A plurality of transducers, closely conforming to the surface of a low-drag ose, are baffle mounted in close pack configurations to eliminate grating lobes. The baffle assembly is mounted outside a pressure hull within a thin acoustically transparent fairing. A plurality of pressure compensators also attach outside the pressure hull. The cavity between pressure hull and fairing is filled with pressure compensating acoustic fluid. Larger portions of unused volume are first filled with a syntactic foam to minimize the amount of fluid required. The pressure compensators balance fluid pressure against external sea pressure to prevent fairing collapse. This array maximizes available nearby internal nose volume thus allowing beamforming electronics to be located within the pressure hull in close proximity to the array elements, connecting thereto via a plurality of short coaxial cables.

Abstract: This invention is a device that permits a flextensional transducer to function after the flextensional transducer experiences a pressure equal to or greater than the pressure found at the survival depth of prior art flextensional transducers. The foregoing is achieved by not bonding at least one end of the transducer's piezoelectric stack to the transducer's shell and having the other end or ends of the piezoelectric stack held in the vicinity of the transducer's shell by a pair of guide rails, etc. This permits the transducer's shell to move away from at least one end of the piezoelectric stack at pressures equal to or greater than the pressure at which the stack would experience tensile stresses in a conventional flextensional design. Thus, the piezoelectric stack will not fracture since it receives no tensile stress.

Abstract: A piezoelectric audible sound generator having a feedback type piezoelectric transducer, an amplifier, and a phase compensator for adjusting the phase shift due to the combination of a bias resistance of the amplifier and equivalent capacitance of the piezoelectric transducer.

Abstract: An electro-hydraulic (EH) actuator for converting electrical inputs into hydraulic output signals is described. The actuator features a pressure balanced design which permits operation at high absolute pressures without performance degradation. Internal portions of the EH actuator are filled with a non-conducting fluid, while a flexible diaphragm provides a movable interface between the fluid and the environment in order to equalize the internal and external pressures on the actuator.

Abstract: A housing for an electroacoustic transducer includes a filling or access port for introducing an inert liquid into the chamber defined by the housing. The access port includes a bubble trap and a vent for extracting gaseous bubbles from the fluid fill. The structure of the access port also comprises a substantially zero spring pressure expansion cavity for the fluid.

Abstract: A window for a sonar transducer housing is formed of an elastomeric plate which is bonded to a mounting ring for securing the window to the housing. The plate is bowed with a convex shape during the molding and the curing of the elastomer. During assembly of the housing, the convex surface of the plate faces inwardly and is depressed to a substantially planar configuration by the pressure of oil within the housing. The compression of the elastomer against the mounting ring inhibits separation of the elastomer from the ring.

Abstract: 1. A tuned electrolytic detector cell comprising an inert plastic casing of enerally cylindrical configuration, a pair of diaphragms closing the ends of said casing, an interior wall portion disposed transversely within said casing and having an opening for fluid communication therethrough, a compliant diaphragm secured to said wall portion and having an aperture centrally disposed therein, an orificed cathode box having a mass therein, attached to the central portion of said compliant diaphragm with the orifice thereof aligned with said aperture thereby to establish fluid communication therethrough, and an anode in said casing.

Abstract: A fiber optic hydrophone for use as an underwater electroacoustic standard. The hydrophone includes a fiber optic acoustic wave detector in one end of the hydrophone which is subjected to incident acoustical waves. A similar fiber optic is in an acoustically isolated compartment where the optic fiber is not affected by the incident acoustical wave. Comparison of light passing through each coil will determine incidence of an acoustical wave on the detector fiber.

Abstract: A hydrophone comprising a tubular thin-walled member of a piezoelectric polymer such as polyvinylidene with electrodes covering the interior and exterior surfaces of the tubular member. An elastomeric core is inserted into the interior of the tubular member and then brought into radial compression against the interior surface of the tubular member.