Abstract: A low frequency sonar projector for use with a projector array having at least one ceramic stack comprised of lead magnesium niobate-lead titanate (PMN-PT) having a Curie temperature Tm approximately equal to the operating temperature of the projector. A mechanism is provided for applying heat to and for controlling the temperature of the ceramic stack to within a fixed operating range. A biasing circuit is included for providing a first electrical signal to polarize the ceramic stack. A driving circuit is also included for providing a second electrical signal to generate an output signal from the ceramic stack. Finally, a mechanism is included for transmitting the output signal from the ceramic stack to a fluid medium. In a preferred embodiment, a PMN-PT ceramic stack is in intimate enclosed contact with an elliptical-shaped outer projector shell. The Curie temperature Tm of the PMN-PT is selected to maximize the electrostrictive effects of the ceramic stack (102) for improving projector performance.

Abstract: A transducer includes an acoustic radiating member for generating acoustic energy in a transmitting medium and a driver member that is pivotally connected to the radiating member. The driver member is for urging movement of the radiating member, wherein such movement generates the energy. Pivoting of the driver member with respect to the radiating member relieves predetermined stress in the driver member. The radiating member may include, for example, a flat element such as a bar, plate or disk, or an I-shaped element. The driver element may include an electroactive material. The driver element may be connected to the radiating element by support apparatus that is fixedly coupled to the radiating element includes a screw having a predeterminedly contoured end that engages a complimentarily contoured recess connected to the driver element for permitting the pivoting. When the support apparatus includes a screw it may be adjusted for supplying a predetermined force on the driver element.

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 broadband electroacoustic transducer is disclosed which provides an improved response over a relatively broad range of frequencies. The transducer includes a plurality of tines extending between the outer circumferential surfaces of a pair of piezoelectric cylinders. The cylinders are disposed about a common axis and are separated by a gap. The tines extend longitudinally across the gap from one cylinder to the other. Each tine is separated from the adjacent tines by a space which is sized to prevent contact between the tines when the cylinders radially oscillate. A pre-stress wrap is disposed over the tines on both sides of the gap to provide a static, inwardly radial force on the cylinders.

Abstract: A composite split cylinder transducer comprises an electromechanical driver and a cylindrical shell having a longitudinal gap. The shell further has a portion, disposed opposite the gap, comprised of a high strength material having increased stiffness. Transducers of this configuration are capable of being employed at greater ocean depths where high hydrostatic pressure conditions exist with little effect on acoustic performance.

Abstract: A bonded insulator flexural transducer for use in sonar applications includes a hollow metal tube having an inner surface, a segmented ceramic electromechanical driver disposed along an inner surface of the tube and a bonded insulator disposed between the segmented driver and the metal tube. The bonded insulator includes a high dielectric strength film, a layer of a binding fiber material, and a layer of epoxy. The dielectric film provides the electrical isolation between the driver and the shell and the binding fiber material provides a reliable bond by effectively trapping the epoxy between the driver and shell.

Abstract: A couplant material for establishing a sonic path of good acoustical impedance between an ultrasonic transducer housing and its crystal, and the housing and a pipe to which the housing is attached. The material is capable of being easily applied at room temperature and withstanding vibration and thermal cycling from cryogenic temperatures to over 500.degree. F. while substantially maintaining its chemical, physical and acoustical properties. A preferred couplant material is a polytetrafluoroethylene grease or perfluoropolyalkylether grease, which have been used previously as lubricants.

Abstract: An ultrasonic oscillating device comprising a base plate and an ultrasonic transducer attached to the base plate. The thickness of the base plate is an integer multiple of approximately a half-wavelength of an oscillation of the base plate in the direction of its thickness under a driving frequency. The base plate may be a quadrilateral such as a square and a rectangle with a length of one side of the quadrilateral being at least a quarter-wavelength of the oscillation. The base plate may be a circle with a length of a diameter of the circle being at least a quarter-wavelength of the oscillation. An ultrasonic washing apparatus comprising a cleaning tank, an ultrasonic multi-frequency oscillator, and the ultrasonic oscillating device is also provided.

Abstract: A reception system including a central core (5) formed of a traction cable (6) and a harness (7) of conducting wires. A fibrous or porous acoustic screen (8) made, for example, from a fibrous or porous material is formed around the core. Sensitive elements are arranged outside this screen, with discontinuous inner electrodes (9) connected to the different wires of the central harness (7), and a common outer electrode (13). A pipe made of a piezoelectric material (12) is formed therebetween. The whole is covered with a protective sheath (2). With such a multi-layered sensitive structure, the manufacturing process of the reception system can be simplified.

Abstract: A transducer includes a first and second spaced apart member, each member having a radiating surface for producing a wave of energy in a transmitting medium in response to a driving force, a plurality of containment devices coupled to each member and extending outwardly beyond at least one radiating surface for communicating the driving force to each member, and a corresponding plurality of driving devices respectively disposed within the containment devices for generating the driving force in response to a change in a predetermined dimension of the driving device. The distance between the members and corresponding distance between the radiating surfaces may be reduced for increasing the bandwidth of the transducer, while the length of the containment device may be increased for accommodating the driving devices in order to maintain a constant driving force. A method for selecting the bandwidth of operation of a transducer is also described.

Abstract: A radially-polarized piezoelectric cylindrical transducer is provided. The ransducer has an electrically conductive end cap affixed with a conductive epoxy to one end of a piezoelectric body and a second cap affixed to the other end. The piezoelectric body comprises a layer of piezoelectric material located between an inner and an outer electrode. The outer electrode has an electrode gap which electrically insulates the end cap from the outer electrode. The unit is electrically conductive and permits the attachment of two electrical leads to its exterior, one to the first end cap and the other to the outer electrode of the piezoelectric body. In an alternative embodiment, two conductive end caps are affixed with conductive epoxy to opposite ends of the piezoelectric body. In this embodiment, the inner electrode has an electrode gap which electrically insulates the second end cap from the inner electrode. One electrical lead attaches to each end cap in this alternative embodiment.

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: A piezoelectric ceramic hydrostatic sound sensor or transducer having high ensitivity to hydrostatic pressure is made by placing a flat plastic disc between two flat layers of green ceramic material, compressing and fusing the layers, heating to a first temperature at which the plastic decomposes, leaving a flat void in the ceramic, and heating to a second temperature at which the ceramic sinters. The transducer is provided with electrodes on its top and bottom surfaces. In a further improvement, ceramic particles are provided which are entrapped in the void; they render the sound sensor sensitive to inertial forces. In yet another improvement, the inside walls of the void are coated with a conductive noble metal connected to a terminal wire, whereby an additional electrode is provided for sensing the electromechanical response of the transducer.

Abstract: A multiport underwater sound transducer including a hollow resilient housing enclosing a volume with at least two ported resonant chambers and a transduction driver disposed within the volume with opposite sides of the driver driving the two chambers. The two ports are set to resonate at slightly different frequencies and the tranducer proudces an additive output at frequencies between the two slightly different frequencies due to phase reversals of oppositely phased sound waves.

Abstract: A transducer assembly providing a conversion between the electrical and sonic energy, the transducer assembly being adapted for operating submerged at great depths in ocean waters. The transducer assembly is formed by a front and back plate which are affixed in one embodiment to the ends of a first mechanically distributed impedance member, a second mechanically distributed impedance member located between the front and the back plate and a transducer of electroacoustical material mechanically coupling the first and second members for imparting sonic vibrations to these members. In a preferred embodiment, the transducer is bonded at one end thereof to the back plate and at the other end thereof to the second member. External hydrostatic pressure present at the front and back plates does not compress the electroacoustical material.

Abstract: A solid-state tunable transducer has been developed by incorporating an elastically nonlinear material, silicone rubber, into an electroacoustic transducer made from piezoelectric ceramics. The resonant frequency and mechanical Q of the transducer are tuned mechanically by applying a uniaxial compressive stress to the composite. The resonant frequency is tuned electrically by placing a piezoelectric actuator into the composite and varying the magnitude of the d.c. bias.

Abstract: A transducer for use in surface ship applications includes a prestress element for providing additional compressive force to an electromechanical driver disposed within the transducer. The transducer includes a shell having inner portions, an electromechanical driver having end portions coupled to inner portions of the shell, and a block prestress element disposed between one of the end portions of the driver and the inner portions of the shell. The block prestress element is fabricated from a shape memory alloy which can be deformed within a first temperature range and reverts back to its original shape when exposed to a temperature above the first temperature range. This characteristic provides for the generation of additional stresses which may be desired for providing protection to the electromechanical driver from unwanted tensile forces.

Abstract: A hydrophone for calibrating lithotripters includes a spot poled disc of piezoelectric material which is mounted on a brass cylinder backing. A coaxial cable is electrically connected to one surface of the disc through the brass backing and the opposing surface of the disc. A mixture of polymeric material and microballoons is provided to protect the interconnection of the center conductor and the opposing surface of the disc and prevent damage due to the incident ultrasonic shock waves. The brass backing is placed in a suitable housing of phenolic material. A process in fabricating the piezoelectric disc and assembling the hydrophone is disclosed.

Abstract: A method of forming a laminated piezoelectric structure is disclosed wherein a plurality of polarized piezoelectric films of vinylidene fluoride and trifluoroethylene are solvent welded together. The solvent welding solution comprises a copolymer of vinylidene fluoride and trifluoroethylene and a suitable solvent. The transducers produced from such a laminated structure are also disclosed.

Abstract: A low-frequency hydrophone for a sonar array comprises at least a lacunary ceramics element with open porosity saturated by a viscous fluid, on which metal electrodes have been deposited. This hydrophone forms a high-pass filter whose cutoff frequency is adjusted by modulating the area of the electrodes. The present invention may find particular application in towed linear arrays and passive sonars.

Abstract: An underwater transducer system reproduces high-fidelity audio signals underwater, and detects and monitors low levels of sound activity, both adjacent to a body of water such as a swimming pool, and in the water. The system includes an underwater housing for a diaphragm that directly contacts the water, a coil assembly movable within the housing and rigidly connected to the center of the diaphragm by a tubular member of the coil assembly engaging a cylindrical boss portion of the diaphragm. The housing can be suspended by an elongated cord member from a wall coping, or mounted within a wall fixture structure. The system can have a source of illumination, a conduit from the source terminating in the housing on the coil axis proximate the diaphragm, and an optical element sealingly protrudes the diaphragm for transmitting light-amplified illumination into the water.

Abstract: There is herein disclosed a piezoelectric composite transducer comprising a plurality of piezoelectric ceramic poles. The plurality of piezoelectric ceramic poles are arranged two-dimensionally so as to form spaces therebetween. Organic films are disposed on both end surfaces of the plurality of piezoelectric ceramic poles so that the spaces forms hollow portions. The hollow portions causes making small its acoustic impedance up to a value close to the acoustic impedance of water or a human body.

Abstract: A hydrophone is provided for use with a hydrophone array enclosed in a streamer cable that is deployed in a body of water. The active transducer elements of the hydrophone are electrically isolated from the sealed metal case in which they are mounted. The signal input and output terminals are protected from short-circuiting due to water invasion of a faulty streamer cable jacket.

Abstract: An underwater acoustical projector has its barrel staves located radially tward of a piezoelectric ceramic driver. The barrel staves are in an hour glass arrangement. The cross-sectional arrangement of the barrel staves is circular at both the top and bottom of the hour glass forming elliptical cross-sections of varying eccentricity between said top and bottom of said staves. The cross-section of greatest eccentricity is located midway between the top and bottom of said staves. The cross-section of greatest eccentricity is located midway between the top and bottom of the barrel staves. This forms a projector with a varying radius of curvature in each of the four 90.degree. quadrants around the axis of the projector. This yields large changes in the resonant frequency.

Abstract: An electro-acoustic transducer comprises two transducer units each having first and second ends, a tubular supporting member disposed between the two transducer units, and a pair of oppositely disposed supporting components between which the transducer units and tubular member are disposed. One of the transducer units is compressively clamped between one of the supporting components and one end of the tubular member, and the other of the transducer elements is compressively clamped between the other of the supporting components and the other end of the tubular member.

Abstract: An ultrasonic oscillating device comprising a base plate and an ultrasonic transducer attached to the base plate. The thickness of the base plate is an integer multiple of approximately a half-wavelength of an oscillation of the base plate in the direction of its thickness under a driving frequency. The base plate may be a quadrilateral such as a square and a rectangle with a length of one side of the quadrilateral being at least a quarter-wavelength of the oscillation. The base plate may be a circle with a length of a diameter of the circle being at least a quarter-wavelength of the oscillation. An ultrasonic washing apparatus comprising a cleaning tank, an ultrasonic multi-frequency oscillator, and the ultrasonic oscillating device is also provided.

Abstract: A split-ring or split-cylinder transducer in which a full or partial boot covering a shell is caused to be looped into the gap of the shell so that outward radial movement and circumferential expansion of the shell causes the boot to also move outwardly thus reinforcing the sound wave generated exterior to the shell of the transducer.

Abstract: The FLEXBAR is a sonar transducer element that is basically a piezoceramic "free-free" flexure bar, but modified so as to radiate as a "monopole" rather than as a "dipole", and retaining the unique properties of being nodally mounted and dynamically balanced. One of the important consequences of this simple modification is the fact that the reaction forces on the FLEXBAR mountings and, the concomitant structure-borne vibrations, are virtually eliminated. This property, and related properties, result in unexpected but significant improvement in the performance of low-frequency, high-power, board-band sonar transducer arrays.

Abstract: The sonar transducer includes a metal core about which is situated a cylindrical piezoelectric ceramic ring element with paper interposed therebetween. In order to improve resistance to fracture resulting from mechanical shock, in one embodiment, the core is reduced in diameter, such that a potting compound can be situated between the paper and the ring. In a second embodiment, the ring element is divided into two individual, axially aligned cylindrical ring subelements with a gasket interposed therebetween.

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 method and apparatus for compensating sensitivity fluctuations in signals received from respective groups of hydrophones for the purpose of subsequent signal processing, the groups being arranged in a predetermined sequence (0, 1, 2, . . . i) to form a transducer arrangement, wherein the received signals are influenced by the sensitivity of the hydrophones and/or the gain of preamplifiers connected to the outputs of the hydrophones. The energy value (W.sub.i) for the received signals of each group of hydrophones is determined and a median energy curve (W.sub.m (.theta.)) is derived from the energy values (W.sub.i) as a function of the sequence of the groups of hydrophones. A correction value is formed for the signals received from each group of hydrophones from a comparison of the respective energy value (W.sub.i) with the energy curve (W.sub.m (.theta.)) and the received signals are corrected with the correction value.

Abstract: A transducer is constructed of a cylindrical shell and at least one pair of piezoelectric sections. Each member of the pair of piezoelectric sections is rigidly bonded to the wall of the cylinder, in a position diametrically opposed from the other member of the pair. Operation as an acoustic source transducer is accomplished by electrically energizing each piezoelectric section in such a manner as to cause the piezelectric sections to elongate and contract, respectively out of phase with one another, along the cylinder length. This causes flexural bending of the cylinder, with the bending being asymmetrical with respect to the cylinder axis. When one pair of piezoelectric sections is used in this manner, the transducer approximates an acoustic dipole radiator, and if more than one pair is used, the transducer can be used to approximate higher order polarized acoustic radiators.

Abstract: A flextensional sonar transducer comprising a first cavity defined by an elliptical shell and end plates covering the two ends of the shell, vibration drive means inside the cavity and coupled between portions of the shell wall at opposite ends of the major axis of the shell, a further cavity connected to the first cavity and an opening between the two cavities for coupling the two cavities for the further cavity to affect the resonant frequency of the first.

Abstract: A ferroelectric ceramic transducer having low density, high compliance and improved electrical properties achieved by the absence of any solid or liquid material in the spaces between the lateral sides of the ferroelectric ceramic posts of the transducer. The ceramic volume-fill of the posts is no greater than sixty percent.

Abstract: This pressure compensating device for a volume of immersed gas is equipped with mobile or deformable walls and includes an immersed compensation bladder. The bladder is secured in a housing and communicates with the volume to be compensated. It is arranged by mounting means roughly at the level of the volume. According to the invention, the housing mounting means for the compensation bladder are arranged to allow the housing to move vertically relative to the gas volume so as to keep the mean front of the bladder folds at the level of the surfaces to be compensated, as the volume may be immersed to different depths.The housing mounting means include an arm hinged about a horizontal axis, and a spring exerting its force on a cable connected to the hinged arm.Depending on the preferred application, the mobile walls enclosing volume to be compensated consist of the acoustic drives of underwater electroacoustic transducers.

Abstract: Various configurations of cylindrically shaped transducers are used as borehole seismic wave sources. The basic class of transducers of this invention has an outer shell that is generally cylindrical, and may be comprised sections. The shell or the sections may be pre-stressed or preformed to encourage certain bending motions. Depending on the configuration of the transducer, it approximates a monopole, dipole, or quadrupole radiator. Various actuating means, including magnetostrictive forces and piezoelectric forces, are used to drive the motions of the transducer. These transducers are especially useful for generating compressional, shear, or other elastic waves in solids. For example, in geophysical applications, the transducers are placed in boreholes for either hole-to-hole or single hole measurements.

Abstract: A high power, low frequency flextensional transducer for underwater use comprises a number of spaced piezo-electric element stacks between opposed inserts. The stacks are placed on the plane through the major axis of an elliptical flexural shell and the inserts are shaped to conform with the elliptical shape. The stacks are assembled with first tapered supports and complementary tapered slides are wedged between the shell inserts and the tapered supports until a required pre-stress is exerted by the shell on the piezo-electric stacks. End-plates are attached to the elliptical shell to complete the transducer; the shell having a compression bonded layer of neoprene applied, including a peripheral serrated lip seal to seal against the end-plate while permitting flexing of the shell. A means to provide wide band-width performance is also disclosed. To extend the range of operational depths the cavity within the transducer is filled with a gas whose vapor pressure can be temperature-controlled.

Abstract: A high power, low frequency flextensional transducer for underwater use comprises a number of spaced piezo-electric element stacks between opposed inserts. The stacks are placed on the plane through the major axis of an elliptical flexural shell and the inserts are shaped to conform with the elliptical shape. The stacks are assembled with first tapered supports and complementary tapered slides are wedged between the shell inserts and the tapered supports until a required pre-stress is exerted by the shell on the piezo-electrical stacks. End-plates are attached to the elliptical shell to complete the transducer; the shell having a compression bonded layer of neoprene applied, including a peripheral serrated lip seal to seal against the end-plate while permitting flexing of the shell. A means to provide wide band-width performance is also disclosed. To extend the range of operational depths the cavity within the transducer is filled with a gas whose vapour pressure can be temperature-controlled.

Abstract: This invention describes an acoustic transducer assembly wherein an extremely high figure of merit (d.sub.h g.sub.h) is obtained as a result of converting incoming acoustic axial stress into radial extensional stress thereby multiplying its effect. The piezoelectric active element is encased in a metal sandwich enclosing two semilunar air spaces which allow the device to withstand extremely high hydrostatic pressure yet still respond to low level sound waves when acting as a hydrophone. The mechanical prestress induced by the differential coefficients of expansion between the metal case and the piezoelectric ceramic element also serves to prevent depolarization aging.

Abstract: A signal sensor automatically compensates for the variations of the static pressure of the medium in which it is placed. The signal sensor comprises one or two assemblies each formed of a piezoelectric sensitive element applied against one face of a flexible plate. The other face of the plate is shielded from the variations of the dynamic pressure to be measured by a material absorbing the vibrations but fairly flexible so as to transmit any variation of the ambient static pressure. This material which may be a porous foam or a fibrous substance impregnated with liquid, fills a tubular apertured sleeve.

Abstract: This electroacoustic transducer has a structure of the so-called "Tonpilz" general type, i.e., comprising a radiating horn, a rear mass and a motor formed by at least one piezoelectric element interposed between said horn and said rear mass, and electrically excited so as to produce a vibration transmitted to the horn. Said piezoelectric element is submitted to an electric field with a direction perpendicular to the main direction of polarization of said piezoelectric material so as to stress the latter in the shear mode.

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 deep submergence, acoustically stable directional transducer uses a wavide and an encapsulant to channel sound. The waveguide forms an air space with a housing so that radiated sound is totally reflected at the air space interface. The encapsulant is matched to the acoustic impedance of the sea water at the intended operating depth to minimize reflection at the encapsulant-to-sea water interface.

Abstract: A hydrophone device is provided with a piezoelectric ceramic-polymer composite of 0-3 connectivity in which the piezoelectric filler comprises a solid solution of PBTiO.sub.3 -BiFeO.sub.3 wherein the solid solution contains 50-80 wt. % of the BiFeO.sub.3. The piezoelectric ceramic-polymer composite has large hydrostatic piezoelectric charge and voltage coefficients which are desirable in hydrophone devices.

Abstract: The underwater sound projector includes a hollow-cylindrical metal housing having a recess with an opening. A non-ceramic flexural disc is supported over the opening. Within the recess is a stack of piezoelectric ring elements. A metal drive head transfers force axially from the stack to an annular area on the disc spaced from the center thereof. Foil electrodes are interposed between the piezoelectric rings and situated at the ends of the stack. A stress bolt clamp connects the drive head to the housing with the stack situated therebetween.

Abstract: An electroacoustic transducer having a truncated hemispheric propagation or esponse pattern is disclosed. The transducer comprises an assembly of fish-bone shaped piezoelectric elements, each characterized by a plurality of rod portions extending from a spine portion. The assembly is pivotally mounted within a liquid filled acoustic window means.

Abstract: A sensor, having a sandwich configuration, is able to sense a transduce out parameter in situ without significantly affecting the parameter. The sensor comprises an inner sheet of a polymer having a transducer property. A conductive layer is deposited on parts of at least one of the two surfaces of the inner sheet. A pair of outer sheets of plastic are attached to each side of the inner sheet. Two layers of conductive material may be deposited on the outer, unattached, surfaces of the outer sheets, one layer on each surface.

Abstract: Electrical signal-receiving transducers for logging tools include a silicon plate having piezoresistors formed thereon and response to deflection caused by pressure waves acting on said plate to generate an electrical signal through a bridge circuit including balancing resistors. Another embodiment of the transducer comprises a curved plate which is supported in a tool cavity for response to a pressure wave to deflect and exert forces on a piezoelectric element to generate a signal proportional to the deflection and a pressure wave causing such deflection. Monopole and quadrupole arrangements of the curved plate may be used for sensing or generating symmetric and asymmetric wave forms.

Abstract: This invention is a multiple segment flextensional transducer shell that is easily and quickly manufactured and modified. The shell may comprise two adjustable, flexible plates and two buttress bars or two J-shaped adjustable, flexible plates. When the buttress bars and plates or the J-shaped members are connected together at or near the nodal points of the transducer, the assembled shell will have the same shape as the flextensional transducer shells used in the prior art. The open ends of the assembled transducer shell are covered with flanges and a boot is placed over the shell and flanges to make the interior of the shell air tight.

Abstract: A hydrophone having a hollow interior with signal electrodes on the interior surface and an electrically conducting coating over the entire outside surface. Signal leads are connected to the inside electrodes and the outside electrically conducting surface is connected to a point of ground potential to form an effective electromagnetic interference shield.