Abstract: An acoustic projector which includes an outer shell formed of a reinforced epoxy resin having a longitudinal slot has an inner reinforcing liner formed of metal to reduce mechanical stress. The liner extends throughout the length of the outer shell and has a longitudinal slot aligned with the slot formed in the shell. An arcuate shaped driver is mounted along a portion of the I.D. of the metal liner and separated therefrom by insulation. In an alternate embodiment, the outer shell is formed of a plurality of overlapping layers of epoxy/graphite strips extending at various angles to increase the Z-axis stiffness.

Abstract: An acoustic projector which includes an outer shell formed of a reinforced epoxy resin having a longitudinal slot has an inner reinforcing liner formed of metal to reduce mechanical stress. The liner extends throughout the length of the outer shell and has a longitudinal slot aligned with the slot formed in the shell. An arcuate shaped driver is mounted along a portion of the I.D. of the metal liner and separated therefrom by insulation. In an alternate embodiment, the outer shell is formed of a plurality of overlapping layers of epoxy/graphite strips extending at various angles to increase the Z-axis stiffness.

Abstract: An acoustic projector which includes an outer shell (8) formed of a reinforced epoxy resin having a longitudinal slot (14) has an inner reinforcing liner (20) formed of metal to reduce stress. The liner (20) extends throughout the length of the outer shell and has a longitudinal slot (22) aligned with the slot (14) formed in the shell (8). An arcuate shaped driver (10) is mounted along a portion of the I.D. of the metal liner (20) and separated therefrom by insulation (24).

Abstract: An underwater acoustic projector comprising one or more cylindrical shell segments (8), each shell segment (8) having an even number of drivers (10) mounted therein, and the method of manufacturing said projector. The shell segments (8) preferably are formed with a longitudinal slot (14) and have arcuate segments (16), preferably of a dielectric material extending along the sides of the slot (14) for retaining the drivers (10) within the shell segments (8). The combined lengths of the driver is between 70% and 90% of the shell segment (8) length.

Abstract: A retractable sensor array system is used to provide a large aperture sen array, such as a sonar array, that receives acoustic energy in a deployment medium. The retractable sensor array system includes one or more sensor array sheets having one or more sensors and a sensor array positioning mechanism for deploying and retracting the sensor array sheet from a platform, such as a ship, submarine, aircraft, space vehicle or medical device. The sensor array positioning mechanism preferably includes a motor that automatically and selectively deploys and retracts the one or more sensor array sheets by rolling and unrolling the sensor array sheets. The retractable sensor array system allows the one or more sensor array sheets to be deployed from various locations on a platform and also in various directions from the platform depending upon the desired usage, platform orientation, position and deployment medium conditions.

Abstract: A small diameter towed acoustic line array comprising a plurality of miniature fiber optic lever hydrophones spaced at preselected locations along the array and held in place by fiber holders. The array hydrophones are enclosed within a tubular outer sheath which is filled with an acoustically transparent fluid. The hydrophones respond to either the pressure mode or the pressure gradient mode, each hydrophone further comprising at least one receiving and one transmitting optic fiber of the same diameter, a covering sheath, a clear elastomer and a small reflector. The information received is transmitted to and processed by a beamformer external to the array.

Abstract: An acceleration insensitive interferometric hydrophone sensor having increased sensitivity comprises a rigid cylindrical support mandrel that is coaxial with and between thin walled sense and reference mandrels. Flanges on the reference and support mandrels form air filled cavities above and below optical reference and sense fiber windings, respectively, that are symmetrically wound on associated mandrels. The walls of the sense and reference mandrels are thin so that they both respond to the same incident acoustic wave signal although 180.degree. out-of-phase. A central collar on the support mandrel provides an acceleration insensitive location for making attachment to the hydrophone. In another embodiment, the reference mandrel is much thicker than the sense mandrel and cavities supporting the sense fiber are caused to operate as acoustic impedance mismatches for rendering the reference fiber winding substantially insensitive to and acoustically decoupling it from an incident acoustic pressure wave signal.

Abstract: A piezoelectric film strip is wrapped a plurality of times around a flexible inert mandrel that has standoff collars on each end. The film-wrapped mandrel is hermetically sealed inside a hollow rigid inert cylinder. Electrodes provide electrical communication with the film strip which forms the active element of the transducer. Variations in hydrodynamic pressure flex the film strip in tension to generate a voltage.

Abstract: An acoustic array having polymer hydrophones is disclosed. The array compes a plastic roll, a plurality of polymer piezoelectric sensors affixed to the roll and electrodes that interconnect the sensors to utilization means such as those found for underwater detection systems or geophysical detection systems such as seismic detectors. The plastic roll has a pliant characteristic so as to readily assume a predetermined shape as well as, preferably, having a strong tendency to unravel and is of a relatively thin material. Similarly, the piezoelectric sensors have a pliant characteristic, are relatively thin, and are affixed to one of the surfaces of the plastic roll. Further, the electrodes have a pliant characteristic, are relatively thin, and are affixed to the same surface of the roll as the sensors.

Abstract: A piezoelectric sensor comprising at least one pair of flexible sensitive elements of great length whose respective electrodes are connected in parallel. The interconnection is provided by interlacing the sensitive elements so that the two electrodes of each of the flexible sensitive elements are alternately in electric contact with the two electrodes of at least one other sensitive element. The sensor may be formed by winding at least one pair of sensitive elements on a support in two spirals of opposite directions with interlacing. The chosen assembly method provides both good mechanical strength and simplifies the electric connections because of the multiple electric contacts between the electrodes.

Abstract: A tubular piezo-electric sensor has at least one sensitive element disposed against an outer surface of a tubular support. A substance whose acoustic impedance is very different from that of the material forming the tubular support is disposed therein and a remaining volume of the tubular support is filled with liquid. Glass fiber cords or open cell foams, for example, are used as the substance, and the liquid may, for example, be that which fills a seismic streamer and, in this case, the tubular support is left open. The tubular support may also be closed at both ends by sealed caps and included in a protective sheath. The dimensions of the tubular support and the material from which it is made are chosen so as to optimize the sensitivity of the piezo-electric sensor.

Abstract: A towed piezoelectric cable having a plurality of receiver element units which are arranged on a nonshrinking flexible core with leaving a buffer zone therebetween, each of said receiver element units having two piezoelectric elements which are polarized in a predetermined direction, and are provided with inner electrodes connected to each other and outer electrodes between which an output signal is produced, respectively, the assembly of said receiver element units and said flexible core being contained in a flexible tube which is filled with an insulating oil.

Abstract: Piezoelectric transducer for the production of, for example, hydrophones, with the transducer including a plurality of sensitive coaxial elements interconnected so as to compensate for the effects of accelerations and deflections.A transducer includes at least one pair of sensitive elements composed of sections of radially polarized coaxial piezoelectric cables having an opposing orientation, with an external armouring of one being connected with an internal armouring of the other, and vice versa. By increasing the number of parts of sensitive elements and selecting the relative disposition, it is possible to improve the immunity of the transducer to noise due to accelerations and deflections, regardless of the direction or the need to license a direction where the transducer is sensitive to such noise. A predetermined number of pairs of sensitive elements can be combined around a central column for accommodating connectors or cables.To be applied, for example, to the production of hydrophones.

Abstract: Underwater piezoelectric arrangement in which it comprises two piezoelectric elements made of piezoelectric ceramic-polymer composites and juxtaposed to form a single layer structure, one of the element(s) having larger hydrophone constant than that of the other element(s), and by noise cancelling of the piezoelectric assembly there can be selectively detected only charges or voltages generated by acoustic waves which acts on each element.

Abstract: A support for an elongated piezoelectric pressure sensor, which is general cylindrical in shape is mounted on a hollow support member that has a thickness and strength selected to meet desired conditions. The elongated piezoelectric pressure sensor is wound in a helical depression on the exterior of the support member, and the support member in turn is filled with a potting material having a bulk modulus of elasticity selected to provide a sufficient flexibility so that the elongated piezoelectric sensing element generates signals that have a desired sign characteristic and improved acoustic response.

Abstract: A pressure wave sensor device is provided including at least two sensitive flexible piezoelectric elements wound in two helices in opposite directions of a tubular support and a method for manufacturing same, said device including a copper conducting ribbon wound helically between the two windings of opposite direction and in the same direction as the underlying winding so as to avoid short circuits at the crossing points of the turns and to improve the electric and mechanical couplings between the two sensitive elements, said tubular support being provided with collector assemblies at regular intervals and wound over the whole of its length with the sensitive elements and the conducting ribbon, the different windings then being cut to the right length at the level of the collector assemblies and connected electrically thereto.

Abstract: An acoustic transducer is provided that uses a layer of magnetostrictive ferromagnetic material having high magneto-mechanical coupling. The ferromagnetic material is adhered to a part of the outer surface of a resilient rod, so that an incident acoustic signal causes a change in stress in the magnetic material and, in turn, a change in the material's magnetization. An electrical coil surrounds the magnetic material and converts the changing magnetization into an electrical signal. A plurality of transducers may be assembled into an array and towed behind a ship to detect underwater acoustic signals.

Abstract: Underwater piezoelectric arrangement in which it comprises two piezoelectric layers made of piezoelectric ceramic-polymer composites, one of the layers has larger hydrophone constant than that of the other layer, and by noise cancelling based on the specific construction of the piezoelectric layers only charges or voltages generated by acoustic waves which act on each layer can be selectively detected. The piezoelectric arrangement may be utilized to provide a piezoelectric cable for use in a submarine earthquake searching or fish finding hydrophone, or an acoustic measuring element under water.

Abstract: A sonobuoy has several components slidably mounted in an elongated tube. The components are longitudinally stacked one above the other at the lower end of the tube when the sonobuoy is in a pre-deployed state and are caused to slide longitudinally upwardly in the tube during sonobuoy deployment to provide a predetermined longitudinal spacing between the components when the sonobuoy is deployed. The components typically include an electronics canister, acoustic wave phase controls and one or more active electroacoustic transducers. The components are attached to a plurality of flexible support cables. The cables are attached at their respective upper ends to the bottom of the canister and are attached at their lower ends to the bottom of the tube. The cables are collapsed during the pre-deployed state and tautly extended during the deployed state. Axial guide strips are affixed to the inner surface of the tube.

Abstract: A long, continuous, constant diameter, neutrally buoyant oil filled line array hose without couplings comprising a plastic inner hose having a layer of conducting and/or optical fibers wrapped helically around and bonded to the outer periphery along the neutral axis thereof. A strength member layer is encased within and bonded to an outer plastic sleeve which covers the conducting layer. Sensors are placed within the inner hose cavity through incisions formed at predetermined locations, attached to the conducting layer, and sensor-conductor junctions are sealed with a waterproof coating; the incisions are then chemically sealed. The hose cavity is filled with an insulating oil providing a continuous, oil filled constant diameter, line array hose devoid of coupling members.

Abstract: A distributed microbending sensor cable is described comprising a core structure having discontinuities or ridges on its surface which ridges extend longitudinally of the core. An optical fiber is wrapped helically about the core in contact with the ridges with the adjacent contact points in one embodiment being a distance apart which is the distortion wave length of the selected optical fiber.In a modification of the sensor cable the distance .LAMBDA. between adjacent contact points is varied along the length of the sensor to impart a weighted characteristic to the sensor response.

Abstract: A long line hydrophone wound with a pair of bifilar ribbons that are connected to a constant current high frequency source.

Abstract: An optical technique for detecting acoustic waves of selected frequency and determining their angle of arrival in a medium such as water. The technique utilizes one or more lengths of single mode optical fiber having a birefringence whose orthogonal axes are helically disposed throughout the length of the fiber at a predetermined uniform pitch. Sound pressure waves of certain frequencies incident upon the fiber throughout its length change its birefringence which affects the relative phase of polarized light components propagating from one end to the other by an amount proportional to the amplitude of the acoustic wave. The twisted optical fiber may be arranged in parallel with other like fibers and axes twisted at different pitches thereby enabling detection of sound waves over a range of frequencies and their angles of incidence.

Abstract: A pressure sensitive line transducer wherein electrical signals are generd by the modulation of the electrical resistance of a coaxial cable due to pressure variations because of an impinging acoustic wave. The signals are extracted via a step-up transformer, amplified, filtered and processed by a computer and displayed to extract information about the acoustic wave.

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.