Abstract: A low frequency underwater sound electro-mechanical transduction bender apparatus for radiating sound at deep submergence depths and including at least one piezoelectric bilaminar or trilaminar beam or disc having opposed support ends; a pair of piezoelectric structures that each have sides that are respectively connected at the opposed support ends of the beam or disc. The piezoelectric bilaminar or trilaminar beam or disc is driven by the pair of piezoelectric structures. The apparatus further includes a housing that contains the piezoelectric bilaminar or trilaminar beam or disc and the pair of piezoelectric structures, as well as an internal fill of a fluid substance.

Abstract: Among other things, in general, a piezoelectric actuator for use in a piezoelectric inertial hearing aid is disclosed. The actuator includes at least one bimorph having a top piezoelectric plate, a bottom piezoelectric plate, and a shim with holed ends that extends beyond the length of the plates for securing to bone across, e.g., the mastoid cavity. Actuators having two or morph bimorphs and kits containing the same are also disclosed.

Abstract: A seismic sensor detects a characteristic of a medium during a seismic survey. The seismic sensor includes a casing; a magnet located inside the casing; a coil assembly located inside the casing, wherein the coil assembly moves relative to the magnet; and a temperature-sensitive device connected to terminals of the coil assembly and configured to improve the damping. The magnet and the coil assembly produce some intrinsic damping and the additional damping introduced by the temperature-sensitive device is selected to counterbalance the temperature-dependent intrinsic damping so that a phase of a recorded seismic signal is compensated for temperature induced magnetic field changes.

Abstract: In one aspect, a method of estimating one of inclination and orientation of a downhole device is provided that includes the features of taking pressure measurements at a plurality of locations on the downhole device in the wellbore, wherein at least one location in the plurality of locations is vertically displaced from at least one other location, and estimating the one of the inclination and orientation of the downhole device from the plurality of pressure measurements. In another aspect, a downhole tool is disclosed that in one configuration includes a device for estimating inclination and/or orientation of the downhole tool that further includes a body containing a liquid therein and a plurality of pressure sensors arranged in the body configured to provide pressure measurements of the liquid in the body, wherein a pressure sensor in the plurality of pressure sensors is vertically disposed from at least one other sensor in the plurality of sensors.

Abstract: The audio resonance device contains a base member having a box shape with an open top side, a resonance element inside the base member having stacked ceramic layers, and at least two contact pieces on a top side, a cover member sealing the open top of the base member, and a number of elastic elements, each contacting a contact piece of the resonance element, and having an end extending through the cover member and contacting a portable appliance for picking up audio vibration from the portable appliance and delivering the audio vibration to the resonance element. The resonance element resonates with the audio vibration, and the base member provides a resonant chamber so that the audio quality from the portable appliance is enhanced. The portable appliance is not required of any modification such as opening holes.

Abstract: The invention relates to a sensor and a system for measuring pressure, variation in sound pressure, a magnetic field, acceleration, vibration, or the composition of a gas. The sensor comprises an ultrasound transmitter, a cavity, and a passive sensor element. In accordance with the invention the sensor includes antenna means for receiving radio frequency signals (f1, f2), and connecting means connecting the antenna to the ultrasound transmitter for using the radio frequency signals for providing energy for driving the ultrasound transmitter.

Abstract: A method for manufacturing a ferrite magnet device including a ferrite body and first and second center electrodes arranged so as to intersect and be electrically insulated from each other and a permanent magnet arranged to apply a direct current magnetic field to the ferrite body and a method for manufacturing an isolator or a composite electronic component, which include the ferrite magnet device. A magnetic force of the permanent magnet is adjusted using a measurement jig and a magnetic force adjusting apparatus while the permanent magnet is fixed to a principal surface of the ferrite body.

Abstract: A method for producing a rigid magnetic circuit component for an electromagnetically operable valve includes: a) providing a base element made of a magnetic or a magnetizable material, b) complete first heat treatment of the base element, c) a local second heat treatment of the base element so as to form a subregion having a microstructure of martensite and residual austenite in the otherwise martensitic base element, and d) installing the finished processed base element as the magnetic circuit component in a magnetic circuit.

Abstract: A sound sensor, a hydrophone including the sound sensor, and a pressure balancing device for using for the hydrophone are provided. The hydrophone includes: a sensor including a sensing part and a pressure balancing part; a printed circuit board (PCB) that is electrically connected to the sensor; a case that houses the sensor and the PCB and that has an opening at one side thereof; an elastic membrane that covers the opening of the case; and a signal line that is electrically connected to the PCB to be extended to the outside of the case. The pressure balancing part includes a diaphragm of a thin film and a support that supports the diaphragm. A pressure balancing hole is formed at one side of the pressure balancing part, and at the inside of the pressure balancing part, a channel that is connected to the pressure balancing hole is formed, and a compressible gas is filled in the channel.

Abstract: A magnetic circuit is made by magnetically attracting a permanent magnet segment of a partially circular arc in cross section to an outer peripheral surface of a center rod, causing the magnet segment in a magnetically attracted state to face a yoke member, using a nonmagnetic supporter to regulate the magnet segment in position, extracting the center rod from the magnet segment in a position-regulated state, and magnetically attracting and fixing the magnet segment to the yoke member.

Abstract: A magnetic circuit includes a cylindrical yoke member having an inner circumferential surface and a collar formed at one end thereof and turned back substantially at right angles, and a plurality of permanent magnet segments of a partially circular arc in cross section having respective outer surfaces attracted magnetically to the inner circumferential surface of the cylindrical yoke member and respective one end faces attracted magnetically to the collar of the cylindrical yoke member. The magnetic circuit is manufactured by a method including the steps of magnetically attracting the permanent magnet segments to an outer peripheral surface of a center rod, causing the magnet segments in a magnetically attracted state to face the yoke member, using a nonmagnetic supporter to regulate the magnet segments in position, extracting the center rod from the magnet segments in a position-regulated state, and magnetically attracting and fixing the magnet segments to the yoke member.

Abstract: Disclosed is an underwater projector projecting a sound underwater. The underwater projector includes a first disk-type resonator unit, a second disk-type resonator unit, and a central space. The second disk-type resonator unit is installed so that a central axis corresponds with that of the first disk-type resonator unit. The central space is set up between the first disk-type resonator unit and the second disk-type resonator unit, and water can enter the central space.

Abstract: A transducer for use in an acoustic energy cleaner is provided. The transducer includes a resonator and a plurality of crystals bonded to a surface of the resonator. The plurality of crystals is configured to be bonded to the surface of the resonator in a staggered arrangement with respect to each other. In one embodiment, the plurality of crystals is bonded to the surface of the resonator in a horizontally staggered arrangement. In another embodiment, the plurality of crystals is bonded to the surface of the resonator in a vertically staggered arrangement.

Abstract: A gel-filled seismic streamer containing a hydrophone housing which isolates a hydrophone element from shear waves and mechanical forces but sensitive to pressure waves. In one embodiment, the gel-filled streamers contains a hydrophone housing with an air pocket at each end for isolating a pressure sensitive hydrophone element from mechanical noise generated by cable movement during seismic data acquisition operations. The hydrophone housing further provides and a protective case to isolate a pressure-sensitive hydrophone element from shear waves. An inlet formed in the protective hydrophone housing enables pressure waves to be communicated to the pressure sensitive hydrophone element inside of the housing. An alternative hydrophone housing for deployment inside of a streamer is also disclosed which fixably positions a positioning hydrophone or seismic hydrophone within the housing using rubber supports.

Abstract: A seismic sensor contains a geophone (4) disposed within a housing (12). The sensor is also provided with locking means (14, 19, 21) that can either lock the geophone 4 relative to the housing, or can allow the geophone to rotate within the housing. The geophone (4) is enclosed in a casing (1) which is so constructed that the overall mass distribution of the casing and geophone is uneven. The casing and geophone assembly thus adopts a preferred orientation when the sensor is unlocked. A liquid can be disposed within the housing, so that the casing (1) and geophone (4) can float when the sensor is unlocked.

Abstract: A speaker comprising: a magnetic circuit provided with a through hole, and a recess formed around the through hole for retaining a magnetic fluid. The speaker further comprises a bearing provided in the through hole and a shaft supported by the bearing to be movable up and down and fixed to a center cap fixed to a voice coil. A gap between the bearing and the shaft is filled with the magnetic fluid. The speaker eliminates a damper, and realizes a very low f0 which has not been obtained before. Furthermore, the magnetic fluid absorbs friction and resonance between the bearing and the shaft, and the magnetic fluid is kept in the recess and is supplied smoothly into the gap between the shaft and the bearing. Thus, generation of abnormal sounds is suppressed and a large amplitude operation is realized in the speakers of the present invention.

Abstract: A gel-filled seismic streamer containing a hydroplane housing which isolates a hydrophone element from shear waves and mechanical forces but sensitive to pressure waves. In one embodiment, the gel-filled streamers contains a hydrophone housing with an air pocket at each end for isolating a pressure sensitive hydrophone element from mechanical noise generated by cable movement during seismic data acquisition operations. The hydrophone housing further provides a protective case to isolate a pressure-sensitive hydrophone element from shear waves. An inlet formed in the protective hydrophone housing enables pressure waves to be communicated to the pressure sensitive hydrophone element inside of the housing. In one embodiment, the pressure sensitive hydrophone element is a hollow gel-filled cylinder that expands radially outward into a second air gap formed in the housing. A protective case is also provided to isolate the hydrophone housing from shear waves.

Abstract: Seismic wave reception device comprising a hydrophone and/or a geophone and method for coupling it (or them) with a solid medium such as the subsoil. The device comprises at least one hydrophone (2) immersed in a closed flexible-walled sheath (7) filled with liquid (8) that is closed at one end by a sealed plug (9) provided with a sealed duct for a cable (10) connecting the hydrophone to a signal acquisition means (E). The sheath is arranged in a cavity (6) and tightly coupled with medium (5) substantially over the total surface thereof, preferably by means of a hardenable material such as cement. A geophone can be placed in the same coupling material in the vicinity of sheath (7) containing hydrophone (2). Application: seismic prospecting or monitoring operations in an underground formation, notably in order to discriminate the seismic upgoing and downgoing waves.

Abstract: A generally cylindrical hydrophone configuration provides compensation for longitudinal accelerations by placing four identical solid piezoelectric transducer elements along its axis with each transducer element being bonded to a head member, two of which are located generally centrally of the cylindrical housing and fastened thereto and two of which are located near the outside edges of the housing and having slight clearance therewith. Flexible polyurethane boots are clamped to the ends of the housing. The volumes between the centrally disposed and outer transducer head members and between the outer head members and the boots are filled with methyl silicon fluid. Each head member is electrically connected to one side of the electrical output, and the junction between the transducer members is connected to the opposite side, both sides being wired to an electrical contact plate located between the two centrally disposed transducer head members, this volume being filled with electrical potting material.

Abstract: A vibration detector is disclosed. The vibration includes a ring (2) closed at its opposite ends by two ring ends (3, 4), that is externally covered with a sheath (11) made from an elastic material transparent to vibrations, two supporting plates (5) with a flexible central part (6) and a reinforced peripheral part (7) resting on the two ring ends. An inner cavity (8) between the two plates (5) is filled with liquid communicating through ports (10) and sheath (11) with the outside environment. Two sensitive elements (9) such as piezoelectric disks for example are fastened to the flexible central parts (6) on their faces of the interior of the cavity (8). The sensitive elements (9) are well protected from the outside environment and their sensitivity is not substantially influenced by variations in the static pressure. The invention has an application for detection of acoustic or seismic waves.

Abstract: A high reliability instrument system includes means for applying a test condition to the instrument and for determining whether the instrument properly responds to the test condition, and means for inhibiting the generation of an instrument output in response to such testing. This provides verification that most of the instrument system components, but not the system output, are properly functioning. The system further includes means for overriding the output-inhibiting function when it is desired to test the entire instrument system including the system output. The instrument system may include a gap-type ultrasonic instrument, with the test condition comprising a pulse applied to one crystal, the effects of which are detected at the other crystal to determine sensor integrity. The system is preferably configured as a two-wire on-off instrument system, in which application of the test condition at a transmitter is controlled by signals applied to the two-wire signal loop at a remote receiver.

Abstract: A hydrophone structure comprises a hydrophone casing within which is mounted a conductive substrate. Sound pressure signals are conducted into the interior of the substrate, on which are mounted piezoelectric crystals on the exterior of the substrate. The volume between the casing and the substrate is nearly filled with a fluid, preferably oil. One or more bubbles of air remain in the volume between the casing and the substrate to permit vibration of the substrate and consequently the piezoelectric hydrophone element.

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: A seismic cable segment is provided having a longitudinal seam for access into the seismic cable, a cable skin lock, a flotation tube for varying the buoyancy of the seismic cable, external stress members isolated from the inside of the seismic cable, and an environmentally safe gel filling the seismic cable.

Abstract: The invention relates to a marine-seismic streamer having a liquid-filled tube (4) in which there are arranged, in the longitudinal direction, hauling cables and flow-obstructing devices including shaped pieces (2) which are spaced apart in the longitudinal direction for dividing the streamer into sections, and hydrophones (5). The shaped pieces (2) are of cylindrical construction with an outside diameter smaller than the inside diameter of the tube (4) such that an annular gap (9) is formed between the tube (4) and each shaped piece (2). The shaped pieces (2) have at least one annular seal (10), the outer diameter of the annular seal (10) corresponding to the inside diameter of the tube (4).

Abstract: An acoustic wave generator has a shockwave source contained in a housing with a volume between the shockwave source and the location at which the acoustic waves exit the generator which is divided into two sub-volumes, each filled with acoustic propagation medium. The location at which the acoustic waves exit the generator is in the form of a deformable cushion which permits the generator to conform to the surface of a subject to be irradiated with the acoustic waves. The liquid propagation medium in both sub-volumes is circulatable, with the amount of liquid propagation medium in the sub-volume forming the cushion being variable.

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: An underwater transducer comprises a piezoceramic transduction layer and a etal substrate with a thin film of viscous fluid between them. The viscous film allows the transduction layer and substrate to expand and contract relative to each other when the laminate bends under increasing hydrostatic pressure as the transducer descends in a body of water. At sonic frequencies, however, the viscous film provides effectively a rigid bond between the transduction layer and the substrate so that they vibrate in unison. The invention reduces hydrostatic compressive loading on the transduction layer and thereby improves performance in deep water applications. A ring on the substrate surrounds and is engaged by the edge of the transduction layer as hydrostatic pressure increases in order to apply enough compressive stress to the transduction layer to prevent peaks in dynamic loading from exceeding the tensile limits of the transduction layer.

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: A self-orienting vertically sensitive accelerometer is disclosed for measuring a vertical component of acceleration independently of the orientation of the accelerometer. The accelerometer of the present invention includes a spherical plastic shell having a plurality of perforations disposed therein and a thin film of metallic coated piezoelectric polymer bonded to the exterior thereof, forming a small diaphragm at each perforation. In response to acceleration a dynamic pressure is developed within a fluid mass partially filling the spherical plastic shell which creates a strain and resultant charge in each small diaphragm of piezoelectric polymer. The vast difference in density between the fluid mass and the air in the remaining volume of the spherical plastic shell permits the charge developed in each small diaphragm under fluid pressure to be attributed solely to the vertical component of acceleration applied to the fluid mass.

Abstract: A piezoelectric seismic vibrator is disclosed which utilizes a hydraulic system to amplify the longitudinal displacement which results from the application of a voltage to a stack of piezoelectric elements. In each disclosed embodiment of the present invention, a stack of piezoelectric elements is mounted so as to bear upon a power piston which in turn acts upon a high bulk modulus substantially incompressible body of fluid, such as mercury. A drive piston is provided having a cross-sectional area which is smaller than the area of the power piston and the pressure within the fluid system acts to amplify the longitudinal displacement of the piezoelectric elements. The movement of the drive piston is then coupled mechanically or fluidically to the earth to generate seismic waves therein. In one depicted embodiment of the present invention each stack of piezoelectric elements is disposed within a fluid filled chamber which is pressurized by means of communication with the borehole fluids.

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 displacement amplifier interconnects a piezoelectric actuator with a displacement member and comprises respective bellows members of differential diameter defining first and second expansible chambers which are liquid filled and respond to linear displacement of a stack of piezoelectric disks to provide an amplified linear displacement to the displacement member. The transducer is particularly useful as a signal transmitting or receiving transducer for acoustic wave generation or measurement for wellbore logging tools.

Abstract: A self-orienting vertically sensitive accelerometer is disclosed for measuring a vertical component of acceleration independently of the orientation of the accelerometer. The accelerometer of the present invention includes a spherical plastic shell having a plurality of perforations disposed therein and a thin film of metallic coated piezoelectric polymer bonded to the exterior thereof, forming a small diaphragm at each perforation. In response to acceleration a dynamic pressure is developed within a fluid mass partially filling the spherical plastic shell which creates a strain and resultant charge in each small diaphragm of piezoelectric polymer. The vast difference in density between the fluid mass and the air in the remaining volume of the spherical plastic shell permits the charge developed in each small diaphragm under fluid pressure to be attributed solely to the vertical component of acceleration applied to the fluid mass.

Abstract: A hydrophone for the detection of sound or vibrational waves, comprising a piezo electric transducer within a Faraday cage such that it is in contact with and yet isolated from a deformable pressure transmitting medium that carries vibrations. The Faraday cage reduces noise interference. The deformable medium is usually a fluid and preferably a vegetable oil, but can also include a silastic compound couple. One side of the Faraday cage is a ground plane of a surface-mount printed circuit board. Components of an electronic circuit for conditioning the signal are mounted on the printed circuit board and include a buffer having an ultra-high impedance input and a very low impedance output. The circuit has a low power draw and is powered by a replaceable battery.

Abstract: A transducer array designed for towing at an extended distance behind a sace vessel includes electroacoustical transducer elements connected in opposition to the active elements of the array. A surrounding acoustic isolation structure effectively isolates the dummy transducer elements from the ambient noise field while permitting cancellations of self-induced noise.

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: 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 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: An echographic technique based method for prospecting of the subsoil or sea bottom and the like, by means of acoustic waves and carried out by the use of an apparatus constitued, in combination of a known acoustic wave transmitting equipment (1) comprising of a body (6, 8) in the inside of which a chamber (9) is formed defined by an internal reflecting surface (7) shaped like a round paraboloid of axis (Y--Y), closed at the base by an elastic diaphragm (5) and filled with a proper liquid, into which acoustic waves are emitted produced by a pair of main electrodes (10a, 10b) associated with an auxiliary discharge priming electrode (11) put between the first ones.

Abstract: An acoustic transmitter for use in a borehole logging tool employs multiple Helmholtz resonators stacked such that apertures in opposite sides of each of the resonators are in linear alignment so as to provide increased acoustic energy output over a broad band of low frequency seismic frequencies.

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: A piezoelectrically-driven, resonant-pipe projector has formed therein vents to broaden the response of certain cavities resonances and to increase the response between these resonances. The projector exhibits a relatively high electroacoustical efficiency, is capable of medium to high power output over the operating band, and is not depth dependent or depth limited.

Abstract: A sensor for acoustic shockwave pulses, such as in lithotripsy, includes a piezo-electric measuring membrane disposed between two coupling membranes. The intervening space between the coupling membranes is filled with a coupling medium for transmitting the acoustic shockwave pulses. The measuring membrane is in a defined condition largely independent of external influences so that flows in the coupling medium or different pressure exertions on the two coupling membranes do not influence the measured signal produced by the measuring membrane.

Abstract: The apparatus according to the invention is all-fiber optic device that produces an output indicative of the gradient of an acoustic wave in water. The device comprises a neutrally buoyant body having a relatively rigid outer case. When it is submerged in water, the motion of the case is the same as that of a water particle in the same vicinity. A fiber optic linear accelerometer produces a signal proportional to the component of acceleration.

Abstract: An acceleration sensor uses a capsule of mercury filling a rigid enclosure with pressure sensors responsive to inertial forces exerted by the mercury on the walls of the enclosure when it is caused to accelerate. The enclosure may have a flexible lining on its walls or contain a flexible bag for holding the mercury. Means are provided for producing a bias pressure in the mercury. The enclosure may be cubic or tetrahedral, for example, and the outputs of the pressure sensors additively combined to produce outputs representing accelerations in required orthogonal directions when these differ from the directions to which the sensors are responsive. A rotational acceleration sensor is also described.

Abstract: A borehole televiewer uses an acoustic fluid which is lubricating, non-toxic, thermally conductive, electrically insulating, non-reactive, tolerant of high temperatures and pressures, impedance-matched to that of the borehole fluids and the tool window, and which has a low kinematic viscosity at low temperatures.

Abstract: A flexible line array transducer assembly for detecting underwater acoustical signals. The assembly includes an array of spaced-apart piezoelectric elements arranged generally in a line and selected to have low cross-coupling characteristics, low sensitivity to incoherent mechanical perturbations in the directions longitudinal and lateral to the axis of the array, and high sensitivity to coherent mechanical perturbations such as acoustical signals. The elements are polarized in a direction generally transverse to the array and each include opposing surface areas which are generally parallel with the linear axis of the array. Electrodes are disposed on the opposing surface areas of the elements and are coupled to conductors which carry signals produced by the piezoelectric elements when the elements are stressed by acoustical signals. A porous, open-cell material is disposed about the piezoelectric elements as an encasement to maintain the elements in place and mechanically isolate the elements.

Abstract: An electroacoustic transducer ring has an inner vibratile surface defining a ring cavity with a plurality of arcuately spaced electrodes affixed thereto. Planar partitions are placed in the ring cavity. The partition edges are parallel to the ring axis and are attached by a resilient strip to the ring inner surface in the arcuate spacing between the electrodes. The partitions have substantially continuous radial surfaces and when the partitions are substantially coextensive in the axial direciton with the ring axis optimal chordal and diametral isolation between the electrodes is provided.

Abstract: An underwater acoustic wave transmitting and receiving unit having excellent characteristics for both transmitting and receiving and providing stable characteristics over long operating periods. A plate-shaped polarized piezoelectric resonator is provided formed of at least one plate made of a complex of fluorosilicon rubber and lead titanate. The resonator is sealed in a rubber casing filled with an insulating liquid matching the water around the casing in acoustic impedance.