Abstract: An element responsive to acoustic particle acceleration for sensing acoustic signals in a region of low acoustic pressure is disclosed. The element may be isolated from acoustic noise when positioned adjacent an acoustic noise generating high acoustic impedance structure by a baffle which provides isolation from radiated and evanescent acoustic signals and structure vibration.

Abstract: Controlled phase marine seismic subarray for use in a marine seismic array and methods for constructing such subarray are provided. A controlled phase marine seismic subarrays of the present invention are arranged to operate at a preselected depth and to provide generally downgoing (for angles of emergence from the array that are of interest) far-field pulses having phase spectra that match the phase spectrum of the vertically downgoing far-field pulse up to a ghost-notch frequency. The methods select the depth of operation and type of sources for the subarray, select a maximum number of identical elements and spacing based upon the highest incidence angle and frequency for which phase control is desired, and construct a plurality of parallel, linear, subarrays.

Abstract: An adhesion system utilizes a pair of liquid suction systems for adhering a lanket transducer array to the external hull of a vessel. Both liquid suction systems can be individually controlled. The first suction system produces a low liquid pressure under rigid saucer-like shells and causes these shells to press against the hull surface. The second suction system operates similar to the first and is located in the area surrounding the shells. In operation it is possible to enhance the adhering ability of the system by maintaining a lower pressure in the first system. This is feasible due to the rigidity of the material in the first system.

Abstract: A side-looking sonar transducer which has sound absorbing material extending forwardly of the active surface of the transducer elements to diminish the acoustic response over a predetermined zone for reducing the effect of erroneous reflection signals. The surface of the sound absorbing material has a series of sharp peaks and valleys.

Abstract: An acoustic array of special utility in deep operating antisubmarine torpedoes comprises a plurality of individual transducer elements supported by a back-plate member. An acoustic window made of an elastomeric or plastic material is mounted against the front faces of the transducer elements and forms part of the water-proof housing of the torpedo. The backplate provides abuttive support to the transducer elements against crush pressure exerted by ambient water against the acoustic window. Inserts, made of an acoustic decoupling material which exhibits high crush strength characteristics, are interposed between each transducer element and the backplate. The backplate is made of body sections having interposed therebetween very thin layers of a compliant material, with the layers bondingly confined between the body sections. The compliant material is chosen to be of a type which damps acoustic vibrations which may be present in the backplate by the mechanism of "coulomb friction damping".

Abstract: A wideband, derivative-matched, continuous aperture acoustic transducer includes a first sensor area having a predetermined spatial shading and a second sensor area having a spatial shading which is the spatial derivative of the spatial shading of the first area; the first and second spatial shaded areas are superimposed and co-extensive along the sensing axis.

Abstract: A seismic sensor platform comprises an open frame and a plurality of seismic motion sensors vertically positioned in a common horizontal plane in spaced relationship around the periphery of the open frame. A spike associated with each of the sensors extends beneath the open frame for anchoring each of the sensors in the earth. The frame includes a shield for protecting the sensors from physical damage and for shielding them from seismic noise. Second and third pluralities of horizontally positioned sensors may be provided on the frame, orthogonally positioned with respect to each other to sense orthogonal components of reflected seismic waves. The sensors may each be of a different natural frequency to optimize the multifrequency output of the sensor array.

Abstract: A hydrophone array employing a plurality of laser sources coupled onto a single optical fiber communications link. A matching plurality of optical fiber resonant rings, each having a resonance peak at a wavelength substantially equal to the center wavelength of one of the lasers, is selectively coupled to the optical fiber communication link so that substantially only optical energy in a narrow bandwidth around one of the laser center wavelengths is coupled to the corresponding one of the optical fiber resonant rings. Corresponding photodetectors are also wavelength selectively coupled to the optical fiber communications link so that each detector receives only optical energy corresponding to the wavelength of one of the lasers and its corresponding resonant ring, to provide an output signal indicating variations in acoustic pressure at individual resonant rings in the array.

Abstract: A sonobuoy comprises a sonar array mounted on arms 2 that are pivotally connected to a central support 3 and housed by an outer housing 1. Upon entry of the sonobuoy into water a float 8 is deployed which since it is connected to the central support 3 by a line arrests the downward motion of the central support 3. The outer housing 1, by virtue of its inertia, travels on uncovering the arms 2 and positively locating the arms 2 by pulling on lines 17 connected to the arms 2. The use of the motion of the housing 1 to deploy the arms 2 eliminates the requirement for spring powered motors reducing the cost of the sonobuoy.

Abstract: An apparatus for detecting a person in a body of water includes a transmitter for generating an electrical swept frequency signal having a frequency that continuously varies between upper and lower limits, at least one pair of transducers disposed in a body of water including a transmitting transducer connected to receive the swept frequency signal for launching a beam of acoustical waves in response to the swept frequency signal in the body of water and a receiving transducer disposed opposite the transmitting transducer for receiving the acoustical waves and for converting received acoustical waves into an electrical received signal, and a receiver connected to the receiving transducer for producing a detected signal in response to the received signal, for producing a threshold signal in response to the detected signal, and for initiating an alarm when the detected signal falls below the threshold for at least a predetermined length of time.

Abstract: An underwater location system (16) is disclosed having a plurality of locator modules (18), each capable of finding the relative range and bearing of other modules. The modules may be diver mounted, placed on movable objects such as a boat (14) or on fixed positions such as the sea floor (12). Range and bearing to each module of the system is displayed, upon request, on a console (20) which may be hand held or mounted in a diver's instrument console. Each module can interrogate other modules with an acoustic pulse which is answered, after a unique time delay stored in each module, by an acoustic response pulse. Response pulse sources are identified by their arrival in a time detection window set by their unique time delay. Range to each identified transponder source is calculated from a receipt time within each detection window.

Abstract: In seismic surveys at sea, with seismic devices, especially sources of seismic energy being towed behind a vessel and kept at a mutual configuration relative to each other, and with the devices being suspended from a buoyancy member (1) mechanical structure of the equipment permits undesirable forces which influence the sources of seismic energy (3), especially during firing, to be absorbed. Mutually arranged flexible, resilient members (4) are provided between the suspension line of the seismic devices (3) and the seismic devices (3) and/or between the seismic devices. Seismic devices are supported on two or more rigid fastening members (5) and flexible resilient members (4) extend between the fastening members and the suspension line. The flexible resilient members (4) preferably extend in a curved path between the fastening members (5) and the members together form an integrated unit.

Abstract: Methods for the construction of and controlled phase marine source arrays provide phase control for source array pulses radiated into emergence (or incidence) angles of interest. Phase control means that the phase spectra associated with source array pulses radiated in a generally downgoing direction, (i.e. for angles of emergence from the array that are of interest) will match the phase spectrum associated with a vertically downgoing source array pulse out to the "ghost-notch" frequency associated with the vertically downgoing pulse. Although the range of emergence angles over which phase control is possible may be limited by the array geometry, proper attention to and control of array geometry and the radiation characteristics of the individual array source elements provide such controlled phase marine arrays.

Abstract: An apparatus for preventing the transmission of sound in an underwater medium. A resilient housing encloses at least two voids. A first void contains a compliant tube consisting of two T-shaped support structures, each T-shaped support structure supporting a free-bending span designed to resonate at a predetermined frequency. A second void contains a viscous liquid in which metal fibers are suspended. The resilient housing may be surrounded by a rigid cover material which may include means for fastening the apparatus to a surface. The viscous liquid dissipates sound. The compliant tube attenuates the sound waves and decreases the velocity of the sound waves, consequently decreasing the wavelength of the waves.

Abstract: An air deployable, volumetric hydrophone array uses three horizontal booms adiating from a central hub suspended at the array operating depth. Loose lines of hydrophones are hung from pairs of points on the boom structure and hang in arcs approximating catenaries.

Abstract: In a phased array acoustic transducer which has elements of different sizes, the piezoelectric material of large elements is subdiced to produce smaller segments to limit the overall piezoelectric segment size variation within the array to up to 55% or more without significant adverse effect on phased array processsing.

Abstract: An expandable sonar array structure includes a central body with a plurality of radially extendable hydrophone support arm assemblies attached to said body and including a motor-driven drive member to which all the arm assemblies are attached through pushrods. Each arm assembly includes three substantially vertically aligned, radially extending arms carrying hydrophones with top and bottom arms attached to the pushrods through short arms with pivots chosen so that the arms move in opposite directions. The center arm is attached to the lower arm by means of a link which closes a parallelogram arrangement such that the center arm moves essentially in parallel with the lower arm. An additional arm is pivotally attached to the outboard end of the center arm and extends the center arm to essentially the diameter of the upper and lower arms, and its outboard end is attached through a link to the outside end of the upper arm.

Abstract: A piezoelectric ultrasonic array transducer has its individual elements connected to external electronics via a high density interconnect structure which facilitates signal connection and uniformity from array-to-array. The array fabrication process is preferably modified for use with a high density interconnect structure in order to obtain maximum transducer quality.

Abstract: A hydrophone with crossed pairs of geophones is provided with a strong light weight housing allowing use at several thousand feet deep in the ocean while still maintaining good sensitivity. The cruciform housing has a cylindrical portion conforming to each of the four geophones so that each cylindrical wall has small diameter and requires small thickness. The cylindrical portions are joined to a central body to complete the housing.

Abstract: The method and the device are designed to cause the signal of each hydrophone of an antenna to be rid of the component due to the vibrations of a wall close to which the antenna is placed. To this end, a correction signal is deducted from the signal of the hydrophone. This connection signal takes account of the vibrations of the wall measured by sensors placed on the wall, in the vicinity of the antenna. The study of the circuit which enables this correction signal to be given is done by resolving the vibration of the wall into its dominant modes of deformation.

Abstract: A fastening device for fixing seismic circular devices is designed with a rigid, split, annular clamp (4) with an open void facing the seismic device (1) for insertion of at least one shock absorbing member (7) in the void. Such a clamp (4) is provided in the region of the device which is most subjected to strain, where a concentric securing ring (8) is also mounted, about which the clamp is fitted with a shock absorbing member (7) on each side of the ring. One more such clamp is provided on the seismic device (1) in order to distribute the load. This arrangement is especially suitable for use in connection with seismic airguns which are to be fixed at predetermined mutual distances in a frame structure (2).

Abstract: A magnetic heading sensor alignment device for an acoustic towed line array s described. It includes a generally cylindrical non-magnetic piece having a longitudinal opening along its central axis to accommodate the heading sensor. A plurality of longitudinal non-magnetic strips or springs are provided around the cylindrical piece by securing them at the ends of the cylindrical piece to form a cage. This provides a spring-like action when the alignment device including the heading sensor is inserted inside the hose of the towed line array and thus keep the heading sensor aligned during the deployment of the acoustic towed array.

Abstract: An acoustic array, useful for sonar, comprises a plurality of transducing ements which are free floating and not connected to each other. Means are provided for locating the position of each of the transducer elements. The acoustic array may be one-dimensional, that is, a line array, a two-dimensional array, or a three-dimensional array. In another embodiment of the acoustic array, the transducing elements are free-floating but connected to each other by a flexible tether, which limits the range of separation of one transducing element from any of the others. The locator comprises a centrally located element to which there are attached three horizontal rigid arms. On the end of each arm is a high-frequency acoustic transducer. Periodically, each of the transducers transmits a high-frequency broadband pulse. The pulse from each of the three transducers is unique and identifiable.

Abstract: A transducer assembly comprising: a diaphragm; at least one transducer elnt bonded by its head to the diaphragm; a pressure-resistant means, for supporting the transducer assembly; an acoustic isolator mounted about the transducer element and located between the diaphragm and the pressure-resistant means; the material of the acoustic isolator being elastically linear and equal in thickness to one-quarter wavelength of the corresponding operating frequency of the transducer element.

Abstract: The housing of a transducer supports both dynamic and static pressure sensors to obtain depth information as well as pressure wave signals. A semiconductive diaphragm with diffused resistances connected in a bridge is used as the static sensor which is centrally located on an end face of the housing. Several parallel-connected dynamic sensor elements are arrayed around the static sensor. Each dynamic sensor element is an edge supported brass disk with a thin piezoelectric ceramic disk soldered to it such that the disks flex in response to low frequency pressure waves to generate corresponding electrical signals. A low noise amplifier and filter is capacitively coupled to the dynamic sensor array to process hydrophone signals at a frequency below 1 Hz.

Abstract: The disclosure concerns a directional hydrophonic antenna, consisting of several pairs of dipoles formed by omnidirectional hydrophones superimposed in a streamer and keeping the same reference angle for all the pairs of dipoles. The goal sought is achieved by means of a chain of superimposed, directional modules each bearing a hydrophonic sensor on each lateral face and joined by ringed tubular elements through which there goes a central rod made of fiber glass and a strand of electrical connection cables.

Abstract: A low drag nose assembly for use with an acoustic homing torpedo in an aqus environment has at least one planar array mounted in the slanting side of a substantially conical support member and provides a plurality of preformed sonar beams which display an azimuth selectively extending from fore to aft simultaneously.

Abstract: A three-dimensional large scale rectilinear array of hydrophones comprising a plurality of equally spaced, fixed position, omni-directional, electro-acoustic transducers, utilizes aperture steering circuits to create a polar coordinate map indicating the bearing and elevation of incoming sound signals. The attitude and depth of the array is controlled by an array maneuvering system to position the array for maximum signal strength and to rotate the array to a horizontal position for maneuvering in shallow water. The geometric configuration combined with digital signal processing circuits provide improved sound detection threshold over linear and single planar arrays. An acoustically transparent housing is used to enclose the array. The shape of the housing and supporting structural frame are adapted to limit self-induced background noise.

Abstract: An apparatus for positioning a plurality of marine seismic sources in an array. The marine seismic sources are retained in retaining means which are mounted to a frame so that each source is separated from the nearest other source in the array by a predetermined distance. Shock absorbing means are mounted in the frame intermediate each of the retaining means and each other retaining means mounted to the frame.

Abstract: A method of measuring the shear modulus profile of a seabed floor using one or more bottom shear modulus profilers, each having a seisometer package to measure the seabed motion in three dimensions and a sensor for measuring the pressure at the seabed floor, placed on or below the seabed floor, and a means for converting the measurements derived therefrom into a shear modulus profile.

Abstract: An apparatus and allied method for detecting the presence of submerged, possibly distressed swimmers in a body of water employs a plurality of pairs of transducers arranged on opposite sides of the body of water. Pulsed sequential excitation of the transducers is employed to monitor the body of water. A person disposed between a pair of transducers interrupts the transmission of ultrasonic waves. An alarm is triggered upon the interruption of the ultrasonic waves or after a delay to avoid false alarms, warning of the presence and location of a submerged, lingering swimmer even in the presence of other active swimmers in the body of water. The same apparatus can be employed as an intrusion detector to detect unauthorized entry of a person into an unguarded body of water.

Abstract: An omnidirectional acoustic transducer achieves a broadband radiation or reception pattern with high efficiency by using several transducer rings located side-by-side with each ring comprising a plurality of radially directed individual transducer elements. The transducer elements in each of the rings are tuned to a particular natural frequency and are designed accordingly. Within each ring the transducer elements are energized in phase with one another. The natural frequency of the individual transducer elements differs from one ring to the other.

Abstract: A focussing transducer for the destruction of objects internal to a patient's body by pulses of ultrasonic waves. The transducer comprises a concave transducer surface which is divided into areas and there is a control means which can selectively activate the areas of the transducer so that the waveform arriving at the focus can adjusted.

Abstract: The present invention is directed to an ultrasonic device comprising a plurality of transducer elements arranged in rows and columns and acoustic insulation material maintained between each two adjacent rows of transducer elements. The ultrasonic device comprises (i) a plurality of rows of the transducer elements, each row being disposed on an imaginary circle, (ii) a plurality of circular plates each supporting one of said rows and (iii) spacers for spacing adjacent plates of the plurality of plates at a predetermined space interval, thereby forming a cylindrical array.

Abstract: A hydrophone assembly for use in a marine streamer cable comprising a housing adapted to be mounted in the cable, such housing having a cavity containing a moldable material, an acoustic energy transducer positioned in the moldable material and a rigid body positioned adjacent to the housing such that the rigid body covers a portion of the cavity.

Abstract: A baffle for use in baffling or reflecting acoustic frequencies in a marine environment wherein a core ply of fiber or fabric reinforced rubber sheet is sandwiched between a pair of plies formed of an elastomeric substance and having fluid filled pockets embeddedly positioned therein in a regular, spaced relationship. The reflector functions to baffle or reflect undesired acoustic frequencies typically in conjunction with the operation of sonar arrays.

Abstract: An apparatus for measuring the shear modulus profile of the seafloor by measuring the motion of the seafloor in three dimensions and the wave induced pressure at the seafloor and converting these measurements into a shear modulus profile using the Yamamoto equation and the linear inverse theory of wave-seabed interaction.

Abstract: A cylindrical array employs rectangular planar array segments which extend in the axial direction when assembled on a cylindrical conducting plate having flat longitudinal portions to which the planar array segments are attached. Each planar array segment comprises two columns of planar transducer elements with each column extending in the axial direction of the cylinder. The acoustic center of each transducer lies on the circumference of a right circular cylinder. The acoustical requirements of a cylindrical array are satisfied to allow multiple beams to be formed with a minimum of complexity and with the same versatility as in the curved array segment cylindrical array embodiment.

Abstract: A transducer array which includes backing and an acoustic window separated by a plurality of elongated parallel rail members having notches in the sidewalls thereof. Notches in adjacent rail members accommodate a stave member which carries a plurality of transducer elements. A stave member may be placed in the notch and slid into position from which it may be easily removed by reversing the process. The design is such that when used with a fairing to provide hydrodynamic shape, the assembly may be free-flooded with the surrounding water medium. In situ replacement of a transducer element may be accomplished by removal of a small section of the fairing and the subsequent removal of one or more stave members.

Abstract: A radiation source launches a radiant pulse of a desired width into a plurality of parallel-coupled optical sensors for modulation by a quantity to be measured. The modulated output from any two sensors taken in all combinations are interferometrically combined to generate a series of time-separated interference patterns. The interference patterns are probed by a photodetector and vectorially combined to provide the vector gradient of the quantity under measurement.

Abstract: A sonar antenna is provided which can serve as the head of an underwater device, e.g., a torpedo, and a method for manufacturing the same. The sonar antenna is formed of a block of syntactic foam rigid enough to withstand submersion hydrostatic pressures. The block has a plurality of housings formed in the outer surface thereof, with at least one electro-acoustic transducer in at least one housing flush with the outer surface of the block. The base of the block is provided with a flanged sleeve by which the antenna can be mounted to the front end of the underwater device, with an acoustic decoupling fitting provided between the flange and the underwater device. The entire block, transducers and flange are surrounded by a sealed envelope which is transparent to acoustic waves. The outer surface of the sealed envelope serves as the outer surface of the sonar antenna and as the front end of the underwater device.

Abstract: The invention is a deployment system for a marine seismic source array. A plurality of sources are suspended at different depths from a float. The system is adapted for deploying the float and the sources into the water and retrieving them for reloading onto the vessel. When the float is positioned on the water surface the sources sink to preselected water depths. The sources are retracted to the underside of the float in the retrieval process.

Abstract: A 60 to 100% coverage of downhole casing condition is obtainable by the improved system comprising, a sufficient number of piezoelectric transducers 1/4 inch in diameter about a probe head, preferably, 40 or more and usually 60-120 piezoelectric transducers located in a housing coupled to an electronic package also in a suitable downhole housing. The system reports all exceptional data and certain selected regular or non-exceptional data, displaying it topside and establishing a permanent record using existing wire line facilities.

Abstract: A hydrophone mount for use with a marine streamer cable having solid foam flotation. The mount comprises a semicylindrical housing having a cavity formed on its outer surface for receiving the hydrophone. The hydrophone is mounted in the recess and the voids filled with an acoustic responsive material. The mount is positioned in a semicylindrical recess formed in the stream cable coaxially with the center of the cable. The stress member and electrical conductors are located at the center of the streamer cable.

Abstract: An assembly for use in seismic surveys of the sea bed is towed behind a vessel and comprises groups of seismic signal transmitters which are towed through the water, being suspended from float buoys which are combined to form one body which may be formed as a sleeve having limited flexibility. The body is formed with a head member shaped for reducing resistance to the water, and connected to a coupling point for a tow wire to the vessel, which point lies forward of the head member and at the same depth as the transmitters.

Abstract: A hydrophone comprises a microphone pivotally mounted on each end of a gimballed tube. A coiled cable connects each microphone with a housing for a receiver. A tube having an external diameter equal to the inside diameter of the cable coil is inserted partially into the coil. The end of the cable is threaded through a lateral hole in the tube and through the interior of the tube into engagement with the microphone or the housing, as the case may be.

Abstract: A passive sonar system which forms multiple receiver beams for detection of possible targets. The transducer array for the system includes a plurality of pairs of transducers, the transducers of each pair lying along a generally radial line emanating from a central point. The output signal from the outer transducer of each pair is delayed by 90.degree. or .lambda./4C relative to the inner transducer, and the delayed signal is combined with the output signal from the other transducer of the pair in a summing amplifier so that only one signal per transducer pair need be sampled by a multiplexer for transmission via a coaxial cable to beamformer apparatus. The concept is applicable to groups of transducers with more than just a pair, i.e., with three or more transducers. Appropriate additional delays are provided with all of the output signals and delayed output signals of a group being received by a single summing amplifier.

Abstract: A structure for support of a volumetric transducer array that self-erects en deployed in water. Dual assemblies of radially arranged telescoping arms are coaxially aligned to support a plurality of linear transducer arrays which are secured to the ends of corresponding arms between the assemblies. The arms are each telescoped outwardly by respective support cables which are tensed by suspending the deployed array between a float and a terminal mass.

Abstract: A novel configuration of a low-frequency lightweight sonar system is described comprising a coaxial assembly of a transmitting transducer and a directional receiving array contained within a cigar-shaped streamlined cylindrical housing less than 1 ft. diameter which operates in the 3 to 4 kHz frequency region and achieves submarine target detection ranges in the order of 20,000 meters with a bearing accuracy within 2.degree.. The small cylindrical streamlined structural assembly results in a very great reduction in drag resistance while it is being towed underwater at high speeds as compared to conventional sonar domes which must be an order of magnitude larger in diameter to accommodate the larger conventional scanning sonar transducers which are several wavelengths in diameter at the operating frequency.

Abstract: A composite layered assembly of piezoelectric polymer layers and printed wiring layers are configured so that plated-through holes make electrical connection from the outputs of a plurality of polymer hydrophones formed on one or more polymer layers to a plurality of output conductors on a single plane after each hydrophone output is amplified in its associated amplifier.