Abstract: An improved invasive acoustic sensor apparatus detects particulate matter in a flow by impingement thereon. The apparatus includes an axially extending probe body having an active length positionable in a flow and a distributed piezoelectric transducer disposed therein. The transducer is acoustically coupled to an interior surface of the body, along substantially the entire active length thereof, and may be a piezoelectric film, piezoelectric tube, or a plurality of electrically parallel connected piezoelectric tube elements. The apparatus further includes an acoustic isolation layer disposed between the probe body and positioning structure to reduce transmission of process wall vibration to the transducer.

Abstract: An active element in a hydrophone includes a piezoelectric hydrophone crystal mounted to a backing plate. The piezoelectric crystal may divided into separate segments. If so segmented, the polarities of the segments are oriented in the same direction. Whether or not segmented, the center portion or segment of the crystal is supported in part by a center pin at its center. Thus, in the presence of a downward pressure, the end portions or segments develop a concave flexure and the center segment, due to the center pin support, develops a convex flexure. With this reverse flexing phenomenon, the center portion segment develops an electrical signal of opposite polarity from those of the end segments. By carefully selecting the areas of the end segments, and electrically coupling the segments so that the harmonics of the various segments are added out of phase, the distortion introduced the harmonics of the various phases subtract.

Abstract: The underwater sound projector disclosed herein employs, as radiating surfaces or pistons, stiff, lightweight panels whose mass is substantially less than the inertial component of the radiation impedance over the operating frequency range. The panels are driven in opposition by a plurality of linear actuators, e.g., piezoelectric stacks, distributed essentially uniformly over the panels so that each stack drives an essentially equal area of the panel and flexing of the panel is avoided. The compliance reactance of the actuators is made to cancel the inertial reactance of the radiation impedance at all frequencies within an at least decade-wide frequency band. In this way, operation, similar to resonance with its high efficiency, is achieved continuously over a wide frequency band.

Abstract: A transducer includes an elongated piezoelectric sensor having only a single integrated mass of piezoelectric material and a pair of relatively longer opposite edges and a pair of relatively narrower opposite edges. The transducer also includes a sensor support that imposes less constraint on one of the pairs of edges than on the other pair.A transducer has two piezoelectric sensors, and a support for supporting the two sensors back-to-back. Each of the sensors being held on opposite edges by a pair of opposite ledges, while two other opposite edges of the sensors are less constrained. The maximum displacement of the two less constrained edges of each sensor are limited by another pair of opposite ledges which are spaced away from the sensor when the sensor is in its normal position.A transducer has two piezoelectric sensors mounted back-to-back on a housing that includes a rib which supports an edge of each sensor.

Abstract: A transducer and a receiver for use in logging-while-drilling operations, having internal pressure adjustment mechanisms to equalize the pressure between the interior of the transducer or receiver, and the well fluids.

Abstract: An acoustic transducer assembly includes a piezoelectric ceramic crystal. The assembly also includes a pair of solid circular metal plates positioned to sandwich the piezoelectric ceramic crystal between them, wherein each of the metal plates comprises: (i) an outer rim circling a concave portion formed in a first surface of the metal plate, the first surface oriented toward the piezoelectric ceramic crystal; and (ii) an epoxy wicking barrier formed in the first surface, adjacent to the outer rim. The assembly also includes an epoxy adhesive interposed between the metal plates and the piezoelectric ceramic crystal, wherein the outer rim of each plate is bonded to the piezoelectric ceramic crystal by the epoxy adhesive, the pair of plates thus forming a cavity between them. The assembly also includes a flexing stop attached to each first surface.

Abstract: A portable ultrasonic underwater sensor 15 has a piezoelectric element 21 disposed in a case 22 constructed as a cylinder 24 and having a truncated cone 25 both being integrally and axisymmetrically formed so as to constitute a vibrator 22A. A piezoelectric element 21 and the vibrator 22A are bonded together with a center of the piezoelectric element 21 matches the center of a reverse face of the truncated cone 25 of vibrator 22A, whereby the vibrator 22A is entirely resonant in a vibration mode in which flexional vibration at the center of the truncated cone 25 is a maximum amplitude, and wherein means for holding the vibrator 22A is located along a vibration nodal line on an external side face of the vibrator 22A.

Abstract: An improved transducer array includes a two-dimensional array of multilayer actuators, capable of producing very high displacement with low input voltage, integrally packaged with conditioning electronics. Preferred microcomposite actuators use multiple layers of stacked electrostrictive ceramics and conductive materials. The actuators are aligned in a two-dimensional array and can be integrated with the conditioning electronics in a variety of packaging systems. A preferred packaging system is a flexible high density interconnected multi-chip module which has the integrated circuit chips disposed in a substrate, interconnection layers disposed thereon and the multilayer composite actuators disposed on the surface of the interconnection structure. The actuators in this packaged array may be optionally addressed individually or in blocks, depending on the application intended.

Abstract: A high frequency transducer capable of transmitting and receiving having an operational range from 100 kHz to 2 MHz, a free field voltage sensitivity (FFVS) greater than -218 dB re 1 V/.mu.Pa (300 kHz), and a maximum hydrostatic pressure rating of 20.68 Mpa (3000 psi). The sensor element is made of lead titanate with a radial mode of 150 kHz being suppressed by the use of a rubber grommet surrounding the lead titanate element. The sensor element is retained within a sensor housing by a plurality of annealed iron wires attached to an annealed iron ring, both of the faces of the sensor housing are then covered with an acoustically transparent window of natural gum rubber. The sensor housing is attached to a non-metallic preamplifier housing made of a rigid polyurethane containing a preamplifier circuit, a transmit protection circuit, and a plurality of relays for switching the preamplifier circuit during the transmit and receive modes.

Abstract: An anti-fouling device comprises a layer of piezoelectric material, preferably a poled plastic material such as a PVDF polymer, for mounting on the hull of a watercraft. The layer has electrodes on opposite major surfaces thereof, and the layers are connected to a power supply comprising a battery and a d.c. to a.c. converter. The converter generates an a.c. voltage at a frequency, e.g., 20 KHz, for causing vibrations of the layer, such vibrations serving to retard the growth of water dwelling organisms in the craft. The layer electrodes are also connected to an a.c. to d.c. converter for converting a.c. energy to d.c. energy suitable for trickle charging the power supply battery. Accordingly, during transit of the craft through the water, water induced hull vibrations cause vibrations of the layer for generating a.c. energy for storage in the battery, which stored energy is used for causing anti-fouling vibrations of the energy generating layer.

Abstract: A method and apparatus is disclosed for making a sliced phased array transducer formed from a single piezoelectric disk which has been bonded to a metal coated support surface. After bonding, the disk and attached metallic coating are cut into a plurality of conductively isolated staves which are then wired into a sequence which allows the array to emit two beams in opposite directions at a depression angle of about 60 degrees. In use, two of the arrays are used adjacent to each other with one emitting beams along the port and starboard sides of the vessel and the other being rotated 90 degrees to emit beams to the force and aft of the vessel, the four beams thereby forming a Janus configuration. Alternatively, the beams could be rotated 45 so that two beams are directed to both the port and starboard sides.

Abstract: A Doppler shift flow meter array detects turbulence in the wake of a submne. Three sets of transmitting and receiving sonic transducers are spaced in a line on a rigid support. The transmitting transducers emit ultrasonic energy which is reflected from particulate matter in a surrounding water medium. The reflected energy is detected by the receiving transducers. A digital Doppler meter associated with each set of transmitting and receiving transducers develops a digital count over a fixed interval that is equal to the Doppler shift between transmitted and received energy. First differences between adjacent pairs of digital Doppler meters are obtained by two digital subtractors, and the second difference between Doppler shifts is obtained by a third digital subtractor. The second difference is non-zero only when ocean turbulence is present, such as produced by a submarine.

Abstract: A system and method provide a low distortion hydrophone. A first known piezoelectric element is mounted so as to receive a pressure signal. A second piezoelectric element is provided with a means of receiving and enhancing the same pressure signal. Since a piezoelectric element is a capacitor, another capacitor is coupled in parallel with the second element to serve as a divider. The output voltage of the combination of the two elements is taken as the difference between the positive terminals of the two elements. Thus, the effect of the pressure enhancer and capacitance divider is to provide a difference in potential between the fundamentals from the two elements, while rendering the amplitude of the second harmonics equal. The two equal second harmonics cancel each other out at the output terminals, while retaining a useful fundamental for further signal processing.

Abstract: An acoustic antenna includes at least one surface sensor formed by a stack of conducting materials and dielectric layers of piezo-electric material enclosed in a sheathing of flexible material. The assembly forms a flat panel 2 mounted against the hull 5 of a navel vessel and takes the shape of the hull. The mounting of the panel on the hull is achieved by two streamlined edging sections 3, 4 while leaving an intermediate water layer 6 remaining between the panel 2 and the hull 5. The sheathing includes an envelope of flexible material filled with a visco-elastic lining material and the piezo-electric material of the dielectric layers of the sensor is preferably a polyvinylidene fluoride film.

Abstract: The invention relates to electro-acoustic transducers comprising a flexible nd sealed transmitting shell referred to as flextensional transducers. A transducer according to the invention comprises one or more electro-acoustic drivers, e.g., a stack of piezoelectric plates 1a, 1b . . . 1n, located inside a flexible and sealed shell. Each piezo-electric driver comprises, at both its ends, a counter-mass coupled mechanically and acoustically with the stack and the ends of the shell by means of an axial threaded rod and two nuts screwed on the ends of the rod. The mass of the two counter-masses and the dimensions of the stack are determined so that the fundamental frequency of the axial oscillations of this mechanical assembly will be close to the natural frequency of the bending oscillations of the shell. An application of the invention is the construction of sonar transmitters.

Abstract: An underwater acoustic transducer for providing high amplitude low frequency acoustic output wherein a plurality of flextensional transducer ovals are formed into a mechanical transformer ring with a corresponding plurality of transducer drivers received therein. A corresponding plurality of radiating surface plates are fixed to the flextensional transducer ovals so as to form a flextensional ring which has disposed on both ends thereof an end plate. Furthermore, a sealing boot is disposed around the flextensional ring which receives the necessary power to operate the transducer drivers so as to vibrate the flextensional transducer ovals to provide the desired motion. Additionally, the flextensional rings can be configured into a tube so as to provide increased levels of acoustic energy.

Abstract: An electro-acoustical transducer arrangement for underwater antennas comprised of a plurality of hydrophones (10) which are arranged at equal distances in a linear array, and are to be disposed vertically above each other on a support. For reasons of a simplified assembly along with good receiving properties, the hydrophones (10), together with a reflector (11) disposed behind them in the direction of incoming sound, are embedded in an acoustically transparent rigid cast enclosure (20) of an elastomer, preferably polyurethane, which can be worked in a casting process. The connecting lines (12) of the hydrophones (10) of the enclosure 20 are combined in a common plug (13), which is accessible on a front end of the rigid cast enclosure (20). The rigid cast enclosure (20) is provided with devices for fastening the enclosure to the support.

Abstract: An underwater sonar projector includes a one piece hollow shell of elliptical cross section having a number of transducer stacks positioned within the shell and compressively prestressed by the shell to vibrate along the major axis thereof which causes the broad surfaces between the small radius ends to vibrate in and out. To resist large external shocks the shell is made somewhat heavier than usual, a center support member or beam is placed along the minor axis of the shell and an adjustable support rod is carried in the beam which is adjusted to a length just sufficient to clear the vibrating surfaces of the projector in normal operation but which functions to limit the inward movement of the shell if exposed to an explosion. The transducer stacks include a number of columns of piezoelectric disks on each side of the support beam which are bonded together, each stack having a tail member fastened to said center support beam and a head member between the disks and the end of the shell.

Abstract: An apparatus for sensing acoustic signals in a liquid wherein an omnidirectional hydrophone exhibits a hemispheric response pattern. A hydrophone, including a transducer element and a transmitting cable, is mounted such that the transducer element is adjacent the forward face of an acoustic baffle including a layer of sound-absorbing material. The rear face of the acoustic baffle is positioned adjacent an acoustic shield including a layer of sound-reflecting material. The transmitting cable is positioned in an aperture in the acoustic baffle and the acoustic shield, and passes beyond the rear face of the acoustic shield. A flow fairing is positioned adjacent the forward face of the acoustic baffle and encloses at least the forward portion of the transducer element.

Abstract: A wave-receiving piezoelectric device for use as, e.g., a hydrophone or a microphone, is constituted by a piezoelectric body having two surfaces sandwiching a thickness and including at least one surface provided with a recess (including a perforation communicating with the two surfaces) set in the thickness direction, and a rigid member having a contact surface and an outer surface opposite to the contact surface and disposed to cover said at least one surface with the contact surface so as to make the recess airtight. As a result, an acoustic pressure received by the outer surface is concentrated and applied onto said at least one surface of the piezoelectric body, thereby giving an improved wave-receiving sensitivity at an enhanced acoustic pressure.

Abstract: An acoustic transducer of the flexural strain gauge type, in which a shell body of oblong section is stressed by a motor along a major axis of this section. A viscoelastic element absorbs the slow deformation of the shell under the effect of submersion. The viscoelastic element exhibits a considerable stiffness at the frequencies of use of the transducer so as to transmit the vibrations from the motor to the shell with adequate efficiency. Such a device makes it possible to manufacture a flexural stain gauge transducer capable of withstanding considerable submersion without the motor fracturing and the efficiency of which is greater than 75%.

Abstract: An array plate for use in an underwater craft. The craft having an array of sonar elements which has a selected range of operating frequencies. The array plate having at least one layer of material in which the layer(s) of material are designed to have selected natural frequencies of vibration throughout the range of sonar operating frequencies. The natural frequencies resulting in standing waves having selected wavelengths that develop along the layer(s) of material. The sonar elements are mounted upon the layer(s) of material such that adjacent sonar elements are spaced apart a distance of one half the average wavelength of the standing waves.

Abstract: Disclosed is an encapsulated hydrophone assembly for use in a towed hydrophone array. The assembly comprises (1) a hydrophone element having a hydrophone electrical conductor, (2) an insulated input electrical lead and an insulated output electrical lead coupled to the hydrophone electrical conductor, (3) an electromagnetic shield surrounding the hydrophone element and the hydrophone electrical conductor, the input electrical lead and the output electrical lead extending from the electromagnetic shield and (4) a layer of encapsulating material surrounding the hydrophone element, the hydrophone electrical conductor, a portion of the input electrical lead, a portion of the output electrical lead and the electromagnetic shield to thereby form the hydrophone assembly.

Abstract: A low frequency flex-beam underwater acoustic transducer has a base, a flexible beam having one end cantilever mounted on the base, and piezoelectric driving means, for flexurally driving the beam. The piezoelectric driving means operates in the k.sub.31 and/or the k.sub.33 mode.

Abstract: A piezoelectric device has a piezoelectric element (2) with an electrically conductive surface and an electrical terminal (1) spaced from that surface with a resilient, compressible mass of electrically conductive material (9) held captive between the terminal (1) and that surface to form an electrical connection therebetween. Typically, the electrically conductive material (9) comprises filaments, such as brass wire wool, having at least a conductive surface layer and which are resilient in bending so that when compressed they tend to expand and maintain continuous physical and electrical contact with the adjacent restraining surfaces. The low inertia of the resilient filaments and their multiple contact with the adjacent surfaces helps provide the required continuous contact. Thus, the use of a conventional soldered connection to the piezoelectric element and the associated stress related mechanical failure problems or physical access problems are avoided.

Abstract: A hydrophone for a marine seismic streamer has a pressure sensor with outer membrane surfaces on which piezoelectric sensors (4, 5) are secured. The pressure sensor is formed from two spaced steel disks (1, 2) having recesses directed toward one another and which are laser-welded at the edges in a gas-tight manner. The pressure sensor is electrically insulated from its external environment by a synthetic resin coating, which may enclose the entire pressure sensor, including the connecting wires. A method of making the hydrophone is also disclosed. The hydrophone can be manufactured so as to be small in dimensions and weight, is mechanically sturdy and capable of withstanding overload, as well as being protected by the synthetic resin coating against short circuiting and corrosion.

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: A method of fabricating a membrane acoustic device includes utilizing integrated circuit fabrication techniques to form a support structure for a piezoelectric membrane, to pattern interconnect schemes on the membrane and on a semiconductor substrate, and to form electronic components for amplifying and driving signals generated at one or more piezoelectrically strong active areas. The support structure is a lithographically patterned metal layer on the semiconductor substrate. A matching metallization on the piezoelectric membrane is conductively bonded to the metal support structure of the semiconductor substrate. An acoustic cavity area is etched through the semiconductor substrate to the back surface of the membrane. An extremely small membrane hydrophone can thereby be fabricated for operation at frequencies above 50 MHz.

Abstract: An ultrasonic transducer with a selectable center frequency is provided. The transducer is made of a composite including a piezoelectric base and a plurality of elongated rods made of a material having a coefficient of elasticity substantially responsive to a control signal applied thereto. In one embodiment the rod material is a suitable magnetostrictive alloy in which case the control signal is a magnetic field. In another embodiment, the rod material is a suitable shape memory alloy in which case the control signal is a thermal signal. In either case, the level of the respective control signal, i.e., the level of the magnetic field or the temperature level, allows for selectively shifting the center frequency of the ultrasound beam produced by the transducer.

Abstract: A curvilinear wideband, projected derivative-matched continuous aperture acoustic transducer includes a first curvilinear sensor having a predetermined spatial shading which is constrained to zero at its ends and has amplitude continuity between its ends; and a second curvilinear sensor area having a spatial shading which is the projected spatial derivative of the spatial shading of said first area and which has a discontinuous amplitude at its ends; the first and second spatially shaded areas being superimposed and coextensive along the sensing axis.

Abstract: The current invention discloses a construction of a hydrophone body and hydrophone sensors which provides a significantly enhanced wide band frequency sensor capability within the construction of a sensor array towed in a cable. This construction extends a tuned resonator or sensor along the hydrophone body and into an adjacent section of interconnecting cable. This elongated sensor, in the form of a tubular sensor, provides an enhanced, very low frequency sensing capability within the overall hydrophone array, supplementing the frequency range of the encased hydrophone sensor.

Abstract: A dual frequency, polymer hydrophone, array for a submersible vehicle is closed. A mid-frequency transducer array is employed in the forward end of a submersible vehicle. Between the mid-frequency array and a nose portion of the submersible vehicle is a single or multiple board piezoelectric polymer array employed to implement a secondary, high-frequency transducer array. Amplifying and signal conditioning units are mounted adjacent or on one metallic electrode layer or formed integrally thereon to minimize signal lead loss. The piezoelectric polymer material is chosen to have a density coefficient and sound velocity substantially equivalent to an acoustic window in the nose portion of the submersible vehicle and to be substantially transparent to the mid-frequency array. Minimal degradation of the mid-frequency received or transmitted signals occurs due to the transparency of the high-frequency array.

Abstract: A flextensional transducer includes a stack of driving elements disposed ng a linear axis to convert a driving power into vibrational energy. End pieces, disposed at each end of the stack, have outwardly facing arcuate surfaces. A flexural shell, formed into a loop, is disposed to circumscribe the stack and the end pieces to present an elliptical cross-section with the major axis thereof being generally coincident with the stack's linear axis. The shell is reactively coupled to the end pieces at the outwardly facing arcuate surfaces. A pliant assembly is positioned between each end piece and the flexural shell for maintaining conformal engagement between portions of the end pieces and the flexural shell. The pliant assembly is designer such that its stiffness may be adjusted.

Abstract: The invention relates to processes and electro-acoustic transducers for transmitting low-frequency acoustic waves in a liquid. An electro-acoustic transducer according to the invention is a transducer of the double-tonpilz type, comprising two electro-acoustic drivers (1a, 1b) in line on both sides with a central counter-mass (2) and between two horns (3a, 3b). This mechanical assembly is located in a rigid box (4) which is fitted with side holes (5) and which delimits a cavity (7) housing elastic tubes (6) closed at their both ends and filled with gas so that the Helmholtz resonant frequency of the cavity (7) is close and preferably lower than the fundamental frequency of the axial vibrations of the vibrating assembly. An application of the invention is the construction of low-frequency transmitting transducers of the double-tonpilz type with a wide pass-band.

Abstract: An acoustic sensor is disclosed that exhibits a wide linear bandwidth, provides a high signal-to-noise ratio, and that is rugged and relatively inexpensive. The sensor includes a piezoelectric polymeric tape transducer adhered to a portion of the inner surface of an acoustically transmissive shell. The transducer is coupled to a preamplifier within the shell that amplifies the transducer signal for transmission by a cable to a receiver. The preamplifier, transducer, and one end of the cable are encapsulated within the shell to support and protect the assembly.

Abstract: A pressure compensated hydrophone assembly consists of a hollow mandrel that has an outer surface. The central portion of the outer surface of the mandrel defines a concavity. A flexible, resilient piezoelectric film is wrapped several times around the mandrel. The volume between the inner wrap of the film and the concavity on the outer surface of the mandrel serves as a pressure compensation chamber. The hydrophone is responsive to varying hydrodynamic pressure fields but is substantially inert to acceleration forces, localized impacts and variations in hydrostatic pressure.

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 underwater low-frequency sound producer comprises vibrator units each including a magnetostrictive rod formed of a rare-earth alloy, a permanent magnet for providing a magnetic bias to the rod, prestress bolts for prestressing the rod, a coil wound on the rod for causing magnetostriction of the rod corresponding to an input AC signal applied to the coil, and first and second masses on opposite ends of the rod. The vibrator units are arranged seriatim end-to-end to define a polygon or ring centered on an axis. Connection blocks respectively connect the first and second masses of the vibrator units adjacent to each other. Vibration plates are respectively attached to the connection members. Outer and inner cylindrical boots and upper and lower plates define an annular space in which the vibrator units are disposed. The annular space is filled with oil having an acoustic impedance similar to that of the water in which the sound producer is placed for use.

Abstract: An acoustic transducer having impedance matched layers that can be deployed in environments having wide temperature variations. An anisotropic layer provides a low coefficient of thermal expansion orthogonally to the direction of sound wave propagation. The anisotropic layer may be a solid matrix embedded with fibers, such as glass, arranged in a common orientation.

Abstract: During assembly of one or more stacks of piezoelectric drive elements along the major axis of the elliptical shell (30) of flextensional transducer the conventional technique is to apply pressure along the minor axis of the shell (30), insert the stacks together with pre-tensioning wedges, and then release the minor axis pressure. The invention provides a method for assembly flextensional transducers by applying pressure uniformly over the entire outer surface of the elliptical shell (30) so as to extend the major axis of the shell (30); inserting and locating the stack(s) within the shell; and removing the pressure. The shell (30) inserted within the enclosure (34) such that access to its interior is available for insertion of the piezoelectric stacks and sliding movement of the shell (30) relative to the enclosure (34) is possible.

Abstract: An acoustic sensor and projector module for sonar applications includes a first acoustic transducer element operating as a projector to generate an acoustic beam, and a second acoustic transducer element acting as a hydrophone to sense pressure wave returns. When the second acoustic transducer element operates in a sensing mode, the first acoustic transducer element serves in conjunction with a baffle structure to baffle acoustic signals presented to the hydrophone. Similarly, when the first transducer element operates in a projecting mode to generate an acoustic beam, the second transducer element acts in combination with a baffle structure to baffle acoustic signals emitted by the projector.

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: The invention relates to a method for manufacturing an acoustic sensor, and also to the sensor. The sensor comprises a piezoelectric sheet (12) mounted on a support (14) and electrically connected to electrodes (16,18) connected by electrical conductors (20,22) to a measurement device, characterized in that the assembly constituted by the sheet (12) and its support (14) is coated with a one-piece polymerizable coating layer (24) which is preferably electrically insulating, such that the portion (24a) of the coating layer (24) overlying the sheet (12) constitutes a protective layer which is rendered non-detachable or essentially non-detachable from the piezoelectric sheet (12). The method for manufacturing this sensor is extremely simple and inexpensive, and the protective layer is non-detachable.

Abstract: An elastomer support for a sonar transducer includes a ceramic stack electromechanical driver, a pair of rigid support members, and a pair of elastomer layers disposed between the ceramic stack electromechanical driver and the support members. The elastomer support provides effective mechanical stress reduction in the ceramic stack driver, as well as, a simple, reliable heat dissipation means for the transducer.

Abstract: The metal-ceramic actuator includes an electroactive substrate having at least a pair of opposed planar surfaces and a determined thickness, with the ceramic substrate being poled in its thickness dimension. Conductive electrodes sandwich the ceramic substrate and are bonded to its planar surfaces. Metal caps, each having a concave cavity bounded by a rim, are bonded to both planar surfaces of the ceramic substrate. A potential is applied to the conductive electrodes to cause an expansion of the ceramic substrate in its thickness dimension and a concomitant contraction in its planar dimensions. The contraction creates a flexure of the metal caps, which flexures are used to actuate another instrumentality.

Abstract: A compliant cover for use with acoustic source transducers includes a rubber boot bonded to a shell of the transducer. The cover has a groove molded within a surface thereof to allow the shell to expand and contract with reduced resistance. Conventional transducers having rigidly mounted covers disposed on the shell which resist the motion of the shell and decrease the overall efficiency of the transducer.

Abstract: A high d.sub.h piezoelectric composite material useful for utilization for hydrophones is disclosed which includes a matrix of an organic polymeric material and two different inorganic piezoelectric powders dispersed in the matrix. One of the piezoelectric powders has a large .vertline.d.sub.31 /d.sub.33 .vertline. value, such as lead titanate zirconate, and the other piezoelecctric powder has a low .vertline.d.sub.31 /d.sub.33 .vertline. value, such as lead titanate. The average particle size of one of the two piezoelectric powders is at least two times that of the other. The total amount of the two piezoelectric powders is 65-75% by volume based on the total volume of the matrix and the two piezoelectric powder. The volume ratio of the high .vertline.d.sub.31 /d.sub.33 .vertline. piezoelectric powder to the low .vertline.d.sub.31 /d.sub.33 .vertline. piezoelectric powder is in the range of 3:2 to 9:1.

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: Hydrophone transducer elements are mechanically isolated from one another vibration by suspending them in a urethane matrix molded into a cylindrical shape. A metal ring is mechanically locked in an annular slot defined by the cylindrical shaped matrix. The ring is used to mechanically support the assembly for towing. The transducer elements are electrically connected to one another and to an electrical cable independently of this mechanical support.

Abstract: A seismic source for downhole use is disclosed which is formed by an outer tubular member having weighted ends which carries within a coaxially mounted tubularly shaped piezoelectric element. The piezoelectric element is cyclically driven to produce a standing wave having a frequency in the range of 0.25 to 5 kHz and a narrow bandwidth in the range of 5-50 Hz.