Abstract: An interferometer inhibits a received low frequency acoustic signal that is elow the pass band of interest from appearing in the output. The interferometer has a conventional optical hydrophone in the signal leg to sense both the high and low frequencies of an acoustic signal. The reference leg has means for accepting a low frequency acoustic signal to modulate the coherent light path length while inhibiting the desired high frequency signal. On recombining the signals from both the signal and reference legs the low frequency signal appearing in both legs is canceled and only the high frequency signal appearing in the signal leg reaches the output. In an alternate embodiment the reference leg mandrel is placed internal to the sensor mandrel and provides a low frequency compensation chamber.

Abstract: A compact apparatus for transmitting and receiving multiple sonar beams utilizes an acoustic lens to direct plane waves incident in desired directions to collimating lenses for presentation in phase to electroacoustic transducers having planar surfaces. The electroacoustic transducers emit sound waves which are transformed by the lenses into plane waves emergent in the desired directions.

Abstract: A hydrophone streamer that includes several arrays of optical fiber pressure sensors. Each array consists of at least three sensors symmetrically disposed around the inside of the streamer skin to form a vertically-disposed array. Each sensor modulates a coherent light beam in accordance with the instantaneous ambient water pressure. The output signals of the sensors include an AC component due to seismic waves and a DC component due to hydrostatic pressure difference between the sensors of an array. Means are provided to resolve the AC and DC components to determine the arrival direction of the received seismic waves.

Abstract: A seismic cable assembly having an acoustically transparent tubular enclosure has at least one hydrophone electrically connected and positioned within the cable assembly enclosure. The hydrophone is made up of a pair of formed, electrically conductive plates that fit against an insulating seal which also forms a fluid seal, providing a sealed chamber defined by the inside surfaces of the conductive plates. A pair of piezoelectric elements are interconnected and positioned within the sealed chamber, one element mechanically and electrically connected to the inside surface of one of the conductive plates and the other piezoelectric element mechanically and electrically connected to the inside surface of the other conductive plate. When pressure is applied to the conductive plates, they deform, causing the piezoelectric elements to flex. When the elements flex, an electrical output is presented on the conductive plates which serve as terminals.

Abstract: An ultrasound transducer for medical pulse echo applications is apodized by causing the level of response to vary as a function of position on the transducer aperture. In a preferred embodiment, the response varies as a Gaussian function of distance from the center or centerline of the transducer so that the response at the edge of the transducer is approximately 30% of the response at the center or centerline. The response may be varied by causing the polarization of a piezoelectric ceramic transducer to decrease as a function of distance from the acoustic axis. In a preferred embodiment the transducer comprises a matrix of parallel rods of piezoelectric ceramic in an inert binder. The polarization of the piezoelectric body may be controlled by locally polarizing regions of the transducer with different voltages or for different periods of time. A polarization profile may also be produced by selectively heating localized regions of a previously uniformly polarized transducer to selectively depolarize them.

Abstract: An expendable sound source provides a cost effective projection of acoustic nergies in the ocean. A tubular housing contains a d.c. motor that locates its shaft coaxial with the housing. Cylindrically-shaped camming blocks engage spurs in a pair of rigid pistons at both ends of the tubular housing to reciprocate them in accordance with the pattern of the camming surfaces and the motor speed. A flywheel on the shafts and journaling supports assure the projection of arbitrary waveforms and a key-and-keyway cooperation between the housing and prevents the pistons turning in the housings. A self-contained, high energy battery pack is actuated by magnetic reed switch to assure reliable long term projection after deployment. Pressure compensation can be included.

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: This invention is an electrical connector held together by flexible magnetic substrates which also form the support for the connector's electrical contacts. The connector has many uses but is especially suitable for the connection between sections of hydrophone streamer cables.

Abstract: Slowly tapering the cone angle as a function of distance along the cone results in a horn transducer that has a sharp focus in the near field and a large depth of field. The horn is simulated by time delaying the excitation pulse sequence to an annular array. An ultrasonic imaging system, particularly for contact B-scanning, uses an annular array to simulate both a horn transmitter and a fixed-focus receiver. This device has good resolution over a large depth of field and is easy to implement.

Abstract: The acoustical energy absorbing baffle has a pair of restricted orifice screens rigidly secured in parallel, spaced relation by a lattice stiffener. The screen-stiffener assembly is immersed in a viscous fluid contained within a tank sealed with an elastic diaphragm. Incident acoustical energy is transmitted through the diaphragm and translated into energy absorbing motion of the fluid through the restrictive screens. A compliant mass is acoustically coupled to the fluid to augment fluid particle velocity through the screens and to further absorb energy.

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: A wide-area acousto-optic hydrophone which uses signal and reference laser beams together with interferometric methods for detecting underwater acoustic signals. The signal beam is distributed across the wide sensing area of the hydrophone using beam folding techniques while being directly transmitted through a sensing chamber filled with an optically transparent bulk material, the refractive index of which varies with the incident acoustic pressure thereby modulating the signal beam. Concurrently, a reference beam of equal length and folded in an identical pattern is directly passed through an adjacent chamber filled with the same bulk material. A microhole joins the two chambers, to expose the reference beam to the same static pressure and temperature fluctuations as the signal beam thus serving as a low pass filter.

Abstract: The thinned arrayed transducer for a sonar system includes an array of sonar elements mounted in rows (layers) and columns (staves) on a structure, preferably cylindrical, to form a checkerboard pattern wherein the spacing between adjacent elements in the rows and the columns is equal to or greater than .lambda..sub.m /2, where .lambda..sub.m is the wavelength of the signal of frequency f.sub.o transmitted in the medium where the sonar is being used. The transducer structure is made from a layered cloth impregnated with a phenol based material, and includes openings in which the sonar elements are mounted. The sonar elements which are effectively a half wavelength in length consist of a cylindrical ceramic section fixed end-to-end to a cylindrical metal section. The metal section is made of a loading metal, such as brass. The transmit-receive circuitry energizes the elements by row using a modulated signal to form a variable sonar beam.

Abstract: An acoustic array for use at high hydrostatic pressures comprises an acouc isolation baffle positioned adjacent to the hull; an intermediate acoustic conditioning module supported over the isolation baffle; and an outer layer containing a plurality of hydrophone units. The acoustic isolation baffle comprises alternating layers of rigid and compliant materials bonded together in sandwich fashion, wherein the compliant layer is provided with a regular pattern of air cells. In adjoining compliant layers the pattern of air cells is translated relative to each other so that the load bearing walls of one compliant layer overlap the open cell regions of the adjacent compliant layer with only a rigid layer disposed therebetween. The acoustic conditioning module comprises spaced coverplates with spacer elements extending therebetween to form a plurality of chambers which contain viscoelastic damping elements bonded to the outer coverplate.

Abstract: An underwater acoustic array comprises an acoustic skirt baffle positioned djacent to a hull surface for reducing the transmission of shipboard noise; an acoustic conditioning module positioned over the acoustic skirt baffle; and an outer layer secured to the acoustic conditioning module and containing a plurality of hydrophone units.The acoustic conditioning module comprises inner and outer spaced coverplates; a plurality of spacer elements extending between the coverplates to form a plurality of closed chambers therebetween; and "tuned" viscoelastic damping elements secured to the outer coverplate.

Abstract: A magnetic drive is provided for a flextensional transducer in order to adapt the flextensional transducer for operation at increased ocean depths without the necessity of liquid filling and complex decoupling devices. In one embodiment an electro-magnetic actuator is positioned between the walls of the flextensional shell and is driven electrically so as to deflect the shell walls outwardly. The magnetic actuator in one embodiment includes a permanent magnet and pole pieces supported on one of the interior walls of the shell, with a moving coil positioned between the pole pieces and supported on a diametrically opposite wall of the shell. In an alternative embodiment, the magnetic actuation may be in the form of a rod of magnetostrictive material between opposing interior walls of the shell, which is actuated by an overwound electrical coil, with the shell being of magnetic material such as magnetic iron.

Abstract: The thinned arrayed transducer for a sonar system includes an array of sonar elements mounted in rows (layers) and columns (staves) on a structure, preferably cylindrical, to form a checkerboard pattern wherein the spacing between adjacent elements in the rows and the columns is equal to or greater than .lambda..sub.m /2, where .lambda..sub.m is the wavelength of the signal of frequency f.sub.o transmitted in the medium where the sonar is being used. The transducer structure is made from a layered cloth impregnated with a phenol based material, and includes openings in which the sonar elments are mounted. The sonar elements which are effectively a half wavelength in length consist of a cylindrical ceramic section fixed end-to-end to a cylindrical metal section. The metal section is made of a loading metal, such as brass. The transmit-receive circuitry energizes the elements by row using a modulated signal to form a variable sonar beam.

Abstract: A mechanoacoustic transducer is described which comprises a plurality of circumferentially spaced contiguous vibratile plate members which are driven in phase by a rotating cylindrical cam. The cam is shaped to provide radial oscillatory displacements of the vibratile plates of sufficient amplitude to generate acoustic power density levels in liquids in the order of 100 kW or more per square foot of radiating surface of the cylindrical transducer. The transducer has a diameter of several inches, and it can be lowered into a flooded hole of such size as is usually drilled in an oil field. The mechanically-driven transducer provides an economical means for transmitting very intense low-frequency acoustic power into an oil-bearing shale or sandstone deposit for the purpose of dislodging the trapped oil and increasing the flow rate out of the sediment within which the oil is entrapped.

Abstract: A deep water explosive echo ranging system capable of detecting high perfance submarines by using favorable acoustic paths available at deep depths. An umbrella hydrophone array is deployed from a sonobuoy to deep depths; an electrical subsystem transmits data from the hydrophone array to a transmitter housed in a surface float unit; a multichannel receiver and signal processing and display apparatus in an aircraft receives and processes radio data signals sent from sonobuoy transmitters; and an explosive underwater charge package is remotely triggered by a command generator in the aircraft.

Abstract: A wide seismic source for use in marine surveys comprising at least two arrays of seismic sources disposed to be towed in a spaced parallel arrangement. Each array includes an elongated float having discrete seismic sources mounted thereon and provided with a steering means to maintain the float in the desired lateral position.

Abstract: A compact, unitary sensor array support structure for use in a water medium omprises a plurality of scissor arms mounted on a support. The scissor arms are extended from the support to expand the sensor array, and are retracted to the support when the array is to be recovered. The support with the scissor arms retracted thereto is slidably housed within a container. Together, the support and the container form a hydrodynamic body which can be transported by towing in the water or removed from the water for transport or storage.

Abstract: A method and apparatus deploys a hydrophone array in a predetermined patt. A master buoy includes a float and an anchor which hold a central portion at a predetermined depth in the water. A number of hydrodynamically shaped glide vehicles are disengaged from the central portion and glide radially outwardly from it. When the glide vehicles come to rest, strings of hydrophones are released and buoyed from the bottom in a preestablished pattern. Acoustic energy impinging on the hydrophones, optionally is fed to a transmitting unit on the float or to a remote installation via a cable lying on the bottom.

Abstract: A cylindrical array radiator that reduces the intensity of energy radiated n undesirable directions. The radiator is constructed so that vertical staves placed on the face of a cylinder are staggered in the vertical direction by a predetermined distance to cancel energy in the undesirable directions.

Abstract: A sonar array consists of a significant number of interconnected disk-shaped transducer projectors operating in the bending mode and packaged in a cylindrical housing including a first or lower section including an electronics and battery package for powering the transducer projectors; a main housing containing the stacked, interconnected transducer elements and having padding of foam material for protecting the transducer elements during deployment and handling; and a rear case section which contains a parachute to control rate and attitude of descent from the launching aircraft, a float or buoy in association with the parachute for providing flotation during operation, and a coiled length of nylon rope for suspending the deployed array at the desired distance below the surface. A retaining line or spring clips are used to hold the transducer elements in the main case section during descent in the water following separation of the rear case section and uncoiling of the nylon rope.

Abstract: A directional hydrophone comprises a plurality of coil elements each disposed in an air gap in a common magnetic circuit. In a first embodiment of the invention two coil elements each have a single degree of freedom of motion which is orthogonal to the other. The force due to an acoustic wave impingent upon the hydrophone is resolved into two orthogonal components by the two coils which give rise to two distinct electrical output signals proportional to the sine and cosine respectively of the angle at which the acoustic wave arrives. In another embodiment of the invention each coil element has two degrees of freedom of motion and the movement of each of the coil elements is resolved into two orthogonal components by the effective length of the coil which varies in a known manner with the angle of coil motion with respect to the polarity of the magnetic circuit.

Abstract: 1.

Abstract: 1.

Abstract: A linear sensor array is deployed horizontally on the ocean floor by first deploying a vertical array, between an anchor and a float from which the array is suspended, and then decreasing the buoyancy of the float gradually as the float is carried away from the anchor by ocean currents. The float is comprised of a suitably large volume of buoyant material such as hollow glass microspheres freely floating inside a liquid filled plastic container. To gradually reduce buoyancy, the microspheres are allowed to flow out through a neck near the top of the container while water is allowed to enter the bottom of the container through a liquid permeable membrane. The diameter of the neck is selected for optimum sinking rate of the float.