Abstract: The sonar transducer is protected from explosion shock by a variable impedance device, such as a metal oxide varistor, connected in parallel with the energy conversion component. The varistor normally has a very high electrical impedance, but becomes conductive upon application of the very high voltage output of the energy conversion component as a result of a rapid increase in mechanical energy, such as would accompany an underwater explosion in the vicinity of the transducer, to limit both voltage and current to a safe level so that the transducer can thereafter operate within acceptable parameters.

Abstract: A sonar projector having a pair of opposed oscillating pistons driven by an electromagnetic assembly is rendered capable of operating at reduced resonant frequency by providing liquid mass loading for the pistons. The mass loading is achieved by utilizing a structure which constricts a body of liquid on one side of the piston. The constricted liquid may be sea water or a liquid sealed within the body of the unit. In accordance with a further aspect of the invention, a seal assembly is provided for the moving pistons which not only provides a sealing function but which also acts to radially center the pistons and to provide an axially directed restoring force thereto during piston oscillation. The electromagnetic assembly, in accordance with still a further aspect of the invention, is formed with a permanent magnet structure arranged in a cylindrical configuration with the opposed pistons on opposite axial ends thereof to reduce magnetic leakage losses.

Abstract: A method of establishing an ultrasonic standing wave in a fluid medium is described in which the standing wave is produced by an acoustic energy output along a path extending through the fluid medium, the frequency of said energy output being changed cyclically while maintaining an essentially constant mean frequency. The cyclic frequency change sweeps said energy output frequency between upper and lower limits that represent a difference of at least one half-wavelength at the mean acoustic frequency over the length of said path, so that a fully resonant standing wave appears in each cycle, regardless of transient ambient variations. For stability, the cycle time of the sweep is maintained substantially greater than the travel time of the acoustic energy output over the length of the path.

Abstract: This disclosure describes apparatus and method for overcoming stroke limitations of moving coil reaction-mass vibration dampers, by recovering armature stroke displacement. The coil housing is selectively coupled or de-coupled to the vibrating structure. If, when the armature reaches its travel limit, sufficient damping energy has not been applied to the structure, the coil-housing assembly is decoupled from the structure while the armature is pulsed back to its zero displacement position. The housing then is re-coupled to the surface, having displaced some determinable distance from its previous location relative to the surface. Additional armature movement in the same direction as the previous armature stroke is applied, thereby generating the needed additional damping force. The resetting of the housing to its normal position vis-a-vis the vibrating structure can occur at a selected time in the damping force-generating cycle when reset does not impart an undesired reaction to the vibrating structure.

Abstract: Hydrophones are installed in each tank of a liquid cargo tanker ship. In the unfortunate event that the tanker collides with an obstacle in the water, the hydrophones detect the shock wave due to the collision. The relative first arrival times of the shock wave at the respective hydrophones are measured and the arrival-time differences between two hydrophones of any two different selected pairs of hydrophones is calculated. Hyperbolic lines of constant time difference are projected on a map of the locations of the hydrophones on the ship. The intersection of the lines of position representing the calculated first arrival time differences marks the location of the impact of the ship with the obstacle.

Abstract: A geophone and a geophone planting tool adapted to engage the outer case of the geophone, to hold it securely during aligning, leveling and implanting into the earth and to release it upon lifting the geophone planting tool from the geophone have matable surfaces which enable forces to be transmitted from the geophone planting tool to the geophone.

Abstract: A laminate acoustic window for sonar systems having a pair of septa sandwiching a core therebetween, the core being made of a low shear high elongation to break material, the septa being formed of a relatively low density, high modulus material. The windows of the invention are characterizied by unusual freedom from attenuation loss over a wide frequency range. The windows are further substantially self damping and avoid thereby a generation of significant quantities of deleterious noise due to self generated vibration and transmitted vibration.

Abstract: An underwater acoustic reflector for sonar applications having a title or her geometric form of fibermetal enclosed in a neoprene waterproof envelope and having surface area free of sharp projections that might puncture the envelope when subjected to elevated hydrostratic pressure and which is supported in the vicinity of sonar equipment to reflect away unwanted noise, to modify the acoustic field pattern, or to adjust hydrophone performance by operating as a baffle in the near field.

Abstract: Alignment restoring apparatus for use with seismic shock generators that includes a support frame, a lift frame supported by the support frame, a seismic generator peripherally supported by the lift frame, and a base plate supported by the life frame and arranged to be impacted by the seismic generator. The alignment restoring apparatus includes biasing means located between the lift frame and the base plate to provide a restoring force upon movement of the frame relative to the base plate whereby the initial relationship between the frame and base plate is re-established assuring that the time lapse from initiating the propulsion of the seismic generator toward the base plate to the time of impact therebetween is repeatable.

Abstract: An acoustic detection device having a parabolic dish antenna for gathering ound waves and providing a first stage of amplification, an exponential horn located at the focus of the parabolic dish antenna for further acoustic amplification, a fluidic gainblock for a final stage of amplification, and acoustic earphones for listening. Either a hand operated latex bulb or a mechanical pump is used to pressurize a plastic fluid storage container that is used to supply fluid to the fluidic gainblock. Within the fluidic gainblock are four or more staged laminar proportional amplifiers having a bandwidth of 0 to 4,000 Hz.

Abstract: Geophones are placed around pipelines to detect third parties, e.g., heavy construction vehicles. Associated computer equipment acquires data from the geophones and discriminates for the frequencies associated with heavy construction vehicles.

Abstract: An apparatus is disclosed for balancing a seismic streamer cable. The housing is comprised of a first and a second valve coupled about the streamer cable. Each valve has a clasp adapted to engage a socket on the other valve to ridigly fasten the valves together about the streamer cable. The housing surrounds and retains weights applied to the streamer cable. An alternate embodiment is disclosed where the weight is integral with each valve. The exterior of the housing is designed to produce laminar flow conditions for the fluid passing over the housing as the cable is under tow, reducing ambient noise detected by the sensors within the streamer cable.

Abstract: A passive hydro-acoustic device for warning sea mammals away from shallow areas consisting of an anchor linearly arranged in front of a shallow area and a plurality of cables attached to the anchor at predefined intervals and extending substantially perpendicular therefrom and sonar reflecters affixed to each of the cables.

Abstract: A system and a method for counteracting marine fouling of e.g. a vessel hull (1) are provided.Electro-mechanical vibration transducers (2, 3) are arranged in pairs adjacent to fixed (clamped) nodal lines (4) on said hull (1), and are driven in an inverted phase relationship in order to provide a water particle movement in a hull parallel direction right outside said nodal lines (4) in addition to the hull perpendicular relative movements right outside said transducers (2, 3).The invention also comprises a combination of the mechanical system above and a special surface coating which counteracts fouling from other organisms than those influenced by said water particle movement in the infrafrequency range.

Abstract: A security window is a laminated pair of polymeric window panels having waveguides sandwiched therebetween for transmission of ultrasonic compression waves. The waveguide transmission medium is glass fibers extending from edge to edge of the plastic panels and distributed in plastic strips which cover the entire window area. The index of refraction of the glass fibers is as identical as possible to that of the surrounding plastics, making the waveguides substantially invisible. A transducer initiates an ultrasonic compression wave which travels the length of the waveguide, and is detected by a transducer at the other end of the waveguide. The received signal amplitude diminishes when the waveguide is damaged and such change is used to trigger an external alarm system.

Abstract: A visualizing method for three dimensional standing wave sound field comprises the steps of mixing into a liquid medium a large number of fine particles of the same density as said liquid medium and exposing the liquid medium containing the fine aparticles to a three dimensional standing wave sound field produced by ultrasonic waves thus causing the fine particles to move to positions where the amplitude of the sound pressure is minimum, the sound pressure distribution of the three dimensional standing wave sound field being visualized by the distribution of the fine particles.

Abstract: An underwater signaling device being removably mounted to the strap commonly found in scuba diving tanks. The device includes two elongated members an one of them being removably secured to the strap while the other one, hingedly mounted to the first one, is urged towards the latter by the spring action of the wound common ends connecting each other. A solid mass is rigidly mounted to the movable elongated member and an impact receiving plate is mounted to the fixed elongated member so that when the movable member is released the impact is taken by the plate and not directly by the tank.

Abstract: A sound source coupled to an acoustic levitation chamber is provided with horn loading to improve efficiency and to protect the sound source from heat. A dish sound source may be used, and the horn may include a half wavelength pathway from the rear of the dish to provide additional efficiency.

Abstract: The invention is a method of determining the acoustic velocity of a drill string in a borehole. An acoustic signal is generated at a first location along the drill string, and detected at a second location. The detected signal is autocorrelated and the time of occurrence of multipath reflections on the autocorrelation record is utilized to determine acoustic velocity.

Abstract: A transducer mounter comprises a portable housing adapted to have a wide variety of transducers fastened thereto. The housing is adjustable and releasably mounted to a boat transom by a suction cup and by an adapter that extends through the boat drain hole. The adapter and suction cup include resepective nuts that releasably hold the housing against the boat transom. Removing the nuts renders the housing and transducer portable as a unit. The present further includes a modified embodiment in which the housing is permanently mounted to the boat, but which, because of the housing design, permits adjustment of the transducer on the housing.

Abstract: A siren comprises a compressed air supply which is deflected by stationary deflectors to exit radially through stator ports. A rotor with spaced ports rotates between the stator and deflector thereby opening and closing the stator ports. Stationary vanes are disposed at circumferentially spaced locations, and constitute together with the deflector plate and stator and rotor housing, plenums. There are fewer rotor ports than stator ports, which generates an out-of-phase acoustical pattern which creates an acoustic combination from the stator ports of an acoustic output at a distance from the siren which is more uniform spatially. The thermoplastic seal between the stator and the rotor has minimal clearance under operating conditions having been run-in and plastically deformed at a temperature higher than for normal operation.

Abstract: A sonar dome having an external wall in which a central layer is formed by a plurality of woven webs of glass fibers impregnated with a resin and by two peripheral layers located on each side of the central layer, the peripheral layers being constituted by a plurality of woven webs of carbon fibers impregnated with a resin.

Abstract: A well-logging laboratory, for use with a well-logging tool which is suspended within a borehole by a wireline, includes a moveable frame upon which the wireless drum is mounted, and a moveable bulkhead is associated with the frame and various well-logging apparatus can be secured to the bulkhead, whereby the frame and bulkhead may be assembled as a modular unit, and moved within the well-logging laboratory as a modular unit.

Abstract: A hosewall terminating apparatus for a streamer section utilizing a load bearing flexible hosewall includes an inner sleeve having radially extending outward protrusions and an outer sleeve having radially extending inward protrusions. With the inner sleeve positioned within the outer sleeve, the radial distance between ends of these protrusions are spaced-apart to provide a gap for the position of the flexible hosewall of the streamer section. The hosewall of the streamer section is secured between these protrusions and the sleeve surfaces when the outer sleeve is reduced in diameter by swaging.

Abstract: A variable depth towed sonar line handling system is arranged to provide a level wind of the sonar cable onto a cable winding drum without significant lateral deflection of the cable. The system includes a boom with sheaves at the inboard and outboard ends and an inboard winch with a cable winding drum. The winch is mounted for axial movement past the boom and is translated axially in synchronism with its rotation so that the fleet angle of the cable remains constant. In preferred embodiments, the winch is located beside the boom and translates fore and aft. This allows the cable to be taken off along the pivot axis of the boom, eliminating cable excursion through the sheaves in boom bobbing. Other features include a fairleading saddle and a combined passive and active shock absorbing system.

Abstract: A reinforcing device to achieve stable fastening points for the inner portion (2) of seismic cables, especially cables that are towed laterally displaced in parallel in relation to the towing vessel and provided with at least two layers of armoring (5,6) intended for absorbing stretch loads on said cable, comprises a fastening means on at least one of the end areas of the inner portion (2), and gripping surfaces for external equipment and shaped with at least two securing chambers (3,4). For assembling the outermost layers of armoring (5,6) of said cable are separated and inserted into one chamber each (3, 4), wherein they are secured to form an integrated connection with said casing (2).

Abstract: An apparatus is described for acoustically levitating an object within a chamber by the application of acoustic energy of a single frequency resonant mode, which enables smooth movement of the object and suppresses unwanted levitation modes that would urge the object to a different levitation position. A plunger forms one end of the chamber, and the frequency changes as the plunger moves. Acoustic energy is applied to opposite sides of the chamber, with the acoustic energy on opposite sides being substantially 180.degree. out of phase.

Abstract: The apparatus and method are utilized in controlling an implanted device, such as a cardiac pacer, by use of acoustic vibrations generated by a tuning fork. These vibrations are applied externally to the skin overlying the implanted device and are sensed by a transducer within the implanted device. The transducer generates an electrical signal of a frequency correlated to the tuning fork frequency. An amplifier and tuned filter are utilized to detect predetermined frequencies within the electrical signals produced by the transducer and to direct the processed signals to a programmable electronic device for control of the implanted device.

Abstract: An apparatus for the detection of the arrival and for the determination of the velocity of disturbances such as shock-wave fronts and/or projectiles. Optical pins using fluid-filled microballoons as the light source and an optical fiber as a link to a photodetector have been used to investigate shock-waves and projectiles. A microballoon filled with a noble gas is affixed to one end of a fiber-optic cable, and the other end of the cable is attached to a high-speed streak camera. As the shock-front or projectile compresses the microballoon, the gas inside is heated and compressed producing a bright flash of light. The flash of light is transmitted via the optic cable to the streak camera where it is recorded. One image-converter streak camera is capable of recording information from more than 100 microballoon-cable combinations simultaneously.

Abstract: This invention relates to an integrated acoustic network system to provide warning of impending groundfall in underground mines. The system includes a plurality of geophones which derive acoustic signals by which the source of seismic disturbances is located, and an array of high frequency piezoelectric sensors which pick up signals from small ground disturbances which precede groundfall. A warning system is provided both at the scene of mining operations and at a central location of impending groundfall and of the location of its occurrence.

Abstract: A control system guides a boring tool in a borehole. The tool has a longitudinal tool axis and includes a driver for advancing the tool axially through the earth and steering mechanism for directing the motion of the tool relative to the tool axis in response to control signals. The control system includes an axial electromagnetic source for generating an axial alternating magnetic field directed along an axial source axis. A sensing assembly remote from the source means includes first and second pickup coils for sensing the alternating magnetic field. Each of the first and second pickup coils has a respective coil axis and is rigidly mounted in respect to the other with their respective axes at a substantial angle with respect to each other, defining a sensing assembly axis substantially normal to both coil axes. Each coil generates a respective null electrical signal when the lines of magnetic flux at the respective coil are normal to the respective coil axis.

Abstract: Ribbon termination member has thread therein for connection to a coupling between sections of the towed array. First and second pins have cylindrically curved front surfaces upon which legs of the flexible ribbon tension member are engaged. The curved surfaces permit transfer of tension loads between the flexible tension ribbon and the pins. The second pin has an extended bearing surface 92 for preventing damage to the ribbon when loads are out-of-line.

Abstract: The subject invention discloses a conventional method and apparatus for classifying terrestrial moving vehicles in which the seismic signal generated by the vehicle is broken into its Rayleigh and acoustically coupled components. The ratio of the Rayleigh component to the acoustically coupled component is used to classify the vehicle as heavy or light.

Abstract: A method and apparatus for gathering a geophone sensor string (10) is provided. The geophone sensor string (10) comprises individual sensors (12) for sensing motion of the earth, an interconnecting cable (14) and ring members (22). A line (30) is secured to a ring member (22) at one end of the geophone sensor string. The line is passed through the remaining ring members on the geophone sensor string and extends through the ring member adjacent the opposite end of the geophone sensor string. Drawing the line (30) in the direction of the arrow (32) lifts the sensors off the ground and gathers the sensors and interconnecting cable in an untangled and compact form for storage. The technique of the present invention is adapted for use with vehicles to eliminate manual labor.

Abstract: A connector assembly such that when a first half of the connector receives a second half, a vent hole is defined therethrough. With the second half disconnected and a third half coupled to the first half, the vent hole is sealed.

Abstract: A visualizing method for three dimensional standing wave sound field comprises the steps of mixing into a liquid medium a large number of fine particles of the same density as said liquid medium and exposing the liquid medium containing the fine particles to a three dimensional standing wave sound field produced by ultrasonic waves thus causing the fine particles to move to positions where the amplitude of the sound pressure is minimum, the sound pressure distribution of the three dimensional standing wave sound field being visualized by the distribution of the fine particles.