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: A cost-effective, producible improved apparatus for and method of fabricag a transducer acoustic window for a marine environment has acceptable acoustic energy transmitting properties and appropriate mechanical properties to withstand the rigors associated with varying velocities of flowing water, fluctuating temperatures, changing ambient pressures, the abuse attendant operations, etc., that are routinely encountered during a prolonged deployment. The acoustic window has a cast CONAP 1556 polyurethane window portion that extends over a hull opening and on a bearing surface rim about the opening. A number of equidistantly, circumferentially spaced stainless steel inserts are molded in the cast polyurethane window portion. Each of the inserts has a threaded outer surface, a machined flat, a longitudinal slot and a countersunk unthreaded bore and each threaded outer surface, machined flat and longitudinal slot mechanically engage the cast polyurethane window portion in an adhering and bonding relationship.

Abstract: An acoustic wave energy generator comprises a body having an internal gas-pressurisable first chamber 1 adjoining a second chamber 2 into which a liquid is introduced to cover a vibratable means 4 which may be a flexible diaphragm and is mounted on the second chamber so as to close an associated opening 5 in the second chamber. After the first chamber 1 is pressurised with a first gas a common closed opening between the chambers is opened to cause communication between the chambers 1,2 to permit a shock wave emanating from the first chamber to impinge on the liquid. As a result, the vibratable means 4 is caused to vibrate so as to produce acoustic wave energy in response to the impingement of the shock wave on the liquid. By using different liquids and/or different heights of liquids in the second chamber the generator may be tuned to provide acoustic wave energy with a relatively narrow chosen frequency range or within a chosen substantially single frequency.

Abstract: A flexural transducer includes a hollow tube that is magnetically driven by a coil/magnet assembly. A magnetic field is provided by passing a current through the coil. The filed passes through an air gap between the coil and the magnet to attract and repel the magnet during alternating portions of the current's cycle. The magnetic transducer driver mechanism permits high drive capability, high temperature operation and provides lower frequency operation than conventional ceramic drivers.

Abstract: An acoustic transducer provides an elongated outer shell made of magnetic material and having a pair of flexural members attached to each other in the elongated direction and having a flexural portion extending normally to the elongated direction and forming a partial enclosure between the two flexural portions, and a magnetic drive located within the partial enclosure and engaging the flexural portions for causing the portions to oscillate flexurally.

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: An electromagnetic or electrodynamic shockwave source for generating acoustic shockwaves has a movable element which can be driven for generating the shockwaves, and a stationary element which is in electromagnetic interaction with the movable element to drive the movable element. A membrane which contains an electrical coil arrangement, the coil being charged with high-voltage pulses to cause the generation of shockwaves, is provided as the movable element. A component containing electrically conductive material is disposed opposite the coil arrangement, and is provided as the stationary element.

Abstract: An immersion-resistant housing adapted to receive a vibratable diaphragm spanning the interior of the housing to divide the housing into first and second chambers includes a first port communicating between the first chamber and the exterior environment. The first port is configured as a tubulation. A second port communicates between the second chamber and the external environment. The tubulation has sufficiently small diameter that water entering therein moves essentially as a piston without breakup. The tubulation is configured to have a volume at least equal to that of the first chamber, and a hydrostatic head of about 32 feet of water is necessary before water can be forced into the first chamber. In the preferred embodiment the diaphragm completely seals the housing against direct communication between the two chambers.

Abstract: A flexural mode acoustic transducer system for use in pulse-echo ranging systems has a radiating plate of which even-numbered antinodal zones, counting from a drive connection to a driving element at the center of the plate, are formed with rings of apertures to reduce the radiating areas of those zones, thus reducing cancellation in the far field, and improving the matching of the device to the atmosphere into which the plate is radiating. The plate is backed by a sound deadening layer on a flange of a transducer housing, from which it is separated by a foil which is non-adherent to the plate, and is preferably covered by an acoustically transparent fabric having a pore size small enough to exclude damaging particulates.

Abstract: An omnidirectional hydrophone having an elastic shell in the form of an ote ellipsoid of revolution having the ratio of its major axis to is minor axis greater than about .sqroot.(2-.nu.) where .nu. is Poisson's ratio of the shell material, wherein the circular circumference of the shell (at different circular parallels of latitude) undergoes strains of opposite sign when the shell is subjected to a pressure change. The differential strains are advantageously measured by an optical fiber interferometer having one leg wound about the equatorial circumference of the shell and another leg spirally wound near one or both of the poles.

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 signalling device with a long audible range is described, which is intended for underwater communication between divers. The device consists of a compact and lightweight horn and a rubber bulb. The horn, which works independently from a diver's supply of breathing air, is filled with water and operated by manually squeezing the rubber bulb.

Abstract: An ultrasonic transducer is described that comprises an oscillatory element (e.g., piezoelectric or electrostatic) having a frequency of oscillation in the ultrasonic region. The transducer includes a conical diaphragm connected at its apex to the center of the oscillatory element. The diaphragm has a rim which defines a concave opening and is responsive to an actuation of the oscillatory element to generate a plane wave in the direction of the concave opening. A faceplate having a small aperture abuts the rim of the conical diaphragm. The diaphragm is concentrically positioned with respect to the aperture and is bonded to the faceplate by a flexible adhesive. An induced plane wave is thereby diffracted by the aperturre and exits therefrom with a substantially omnidirectional beam pattern.

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: An electrodynamic shockwave generator, of the type having a shockwave source formed by an electrically conductive membrane and an electrically driven coil, with the membrane being rapidly repulsed from the coil, causing the creation of a shockwave in an acoustic propagation medium disposed on one side of the membrane, upon the application of a pulse to the coil, wherein at least one of the coil or the membrane contains material which can be placed in a superconducting condition. A coolant, and a member for circulating the coolant are provided for placing the material in at least one of these electrically conductive elements in the superconducting condition.

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: An acoustic transducer which can be made small in size, i.e., in width, length and thickness, so as to fit into a credit card size package. The transducer comprises a flat frame having an opening therethrough. A pair of diaphragms of a piezoelectric plastic material extend across the opening in the frame along opposite sides of the frame. The diaphragms are stretched in at least one direction and are bonded to the frame under tension in the direction of the stretch. The diaphragms are bonded together at a position within the opening in the frame. The diaphragms are coated in both surfaces with conductive metal films. The inner metal films on the diaphragms which are opposed to each other are electrically connected together and the outer metal films are electrically connected together.

Abstract: An acoustic source apparatus has a acoustic transducer that is enclosed in substantially rigid and watertight enclosure to resist the pressure of water on the transducer and to seal the transducer from the water. The enclosure has an opening through which acoustic signals pass and over which is placed a resilient, expandable and substantially water-impermeable diaphragm. A net stiffens and strengthens the diaphragm as-well-as constrains the diaphragm from overexpansion or from migrating due to buoyancy forces. Pressurized gas, regulated at slightly above ambient pressure, is supplied to the enclosure and the diaphragm to compensate for underwater ambient pressures. Gas pressure regulated at above ambient pressure is used to selectively tune the pressure levels within the enclosure and diaphragm so that diaphragm resonance can be achieved. Controls are used to selectively fill, as-well-as vent the enclosure and diaphragm during system descent and ascent, respectively.

Abstract: An acoustic source apparatus has a loudspeaker enclosed within a substantly pressure resistant and water tight enclosure. Acoustic energy from the loudspeaker emanates through an opening in the enclosure. This opening is covered by a resilient diaphragm that transmits the acoustic energy to an aqueous medium. A net constrains the diaphragm to a preselected size and shape. The net further impedes overexpansion of the diaphragm and restrains the diaphragm from migrating due to buoyancy. Additonally, the net stiffens and strengthens the diaphragm, to thereby increase the resonant frequency, impedance and quality factor of the transducer system and decrease the transmission bandwidth of the system. Constraining the transducer diaphragm with the net makes higher transducer source levels possible.

Abstract: A low frequency, high powered underwater sound source includes a housing ing disposed therein, a loudspeaker, a bladder disposed over the loudspeaker for containing a pressurized non-liquid sound transmission medium, a fill system for filling the bladder with a sound transmission medium, a vent system for venting the bladder of a sound transmission medium, a differential pressure sensor for comparing the pressure in the bladder with the ambient underwater pressure, a signal generating system to generate an acoustic signal at the loudspeaker, and a control system for controlling operation of the fill system, the vent system, the differential pressure sensor and the signal generating system.

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: An acoustic signal transmitter for well logging tools and the like comprising a housing having a generally rectangular opening formed therein and defining a fluid filled cavity in which a compliant sheet transmitter member is disposed and is provided in a relaxed condition with a curvature. Opposite ends of the transmitter member are connected to piezoelectric actuators which are responsive to an electrical signal to elongate to stretch the sheet into a generally planar state to generate a pressure pulse in the cavity for transmission through a fluid filled borehole to a formation for, preferably, measuring the shear wave velocity in the formation material.

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

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

Abstract: An arrangement for finding the direction of a sound in a medium has a thin shell structure having a circular symmetry. The structure can flex in response to incident sound energy from the medium to perturb the form of the structure. A membrane of a piezo-electric material with an anisotropic piezo-electric response to distortion is arranged to be distorted by the perturbation of the thin shell structure. The response of the membrane to this perturbation permits the direction of the incident sound to be indicated. The membrane can be of polyvinylidene difluoride with anisotropic properties. The membrane may be formed into a "dome" for example by fluid pressure inside a hemispherical shell closed by the membrane.

Abstract: An underwater acoustical projector consisting of a spaced apart pair of polygonal shaped end plates, a ceramic driver of smaller cross-sectional size than each end plate, positioned between the end plates, and a set of staves secured from one end plate to the other, each stave being bent concavely inwardly towards the driver and being separated from each other by a gap.

Abstract: A transducer which has an astigmatic directional characteristic which depends on its assymetrical stiffness or, respectively, speed of sound of the material of a resonant membrane (2) which is composed of a composite fiber material.

Abstract: A flextensional transducer having an elliptically-shaped shell is compressed at its ends by either piezoelectric or magnetostrictive drive assemblies which are constrained from longitudinal movement by a rigid mount. The compression may be provided by a rigid mount having a gap into which a distended shell and the drive assemblies are inserted. After removing the force producing the distended shell, the mount exerts a compressive force on the ends of the shell. Alternatively, the compression of the shell may be obtained by mechanical forces produced by screw mechanisms forming part of the mount.

Abstract: A seismic source marine vibrator having compound hydraulic cylinders for high and low frequencies is used to generate both low frequency and high frequency acoustic pulses. Low frequency pulses are generated by operating a low frequency radiating surface and a high frequency radiating surface simultaneously. High frequency pulses are generated by operating the high frequency radiating surface alone.

Abstract: A multiple frequency range hydraulic actuator includes a low frequency cylinder with a low frequency actuator piston within. The low frequency piston operates as a high frequency cylinder having a high frequency piston within. The low frequency piston, and high frequency piston operate in conjunction to generate low frequency movement. The high frequency piston operates independently to generate high frequency movement.

Abstract: An ultrasonic transducer assembly capable of being operated in a corrosive and/or abrasive environment that might otherwise degrade transducer performance and/or damage transducer related components. The assembly includes an ultrasonic transducer of the type having a vibratile diaphragm supported at its periphery by a support housing and having the diaphragm center portion spaced a predetermined distance from a protective perforated cover. A channel is provided in the transducer between opposite sides of the vibratile diaphragm to avoid temperature induced pressure differentials between gases (air) present in the space immediately adjacent opposite diaphragm surfaces. A plastic film is adhesively attached to the outer surface of this diaphragm-protecting cover and the entire transducer is enclosed within an outer housing. A flexible seal engages the plastic film and an outer housing surface.

Abstract: A flexcompressional acoustic transducer is set forth. In the preferred and illustrated embodiment, multiple parallel magnetostrictive rods provided with coils are coupled through a plate affixed to a radiating element. The radiating element in one embodiment is an elongate hollow cylinder which is closed at both ends. Vibrations from the magnetostrictive members cause the cylinder to radially flex, creating an omnidirectional acoustic wave transmitted radially outwardly, the apparatus being positioned in a sonde for connecting an acoustic wave front through the wall of the sonde for transmission into the surrounding wellbore fluids and the adjacent formations.

Abstract: Wide pass band elastic wave omnidirectional transducer.It comprises a magnetostrictive material membrane (34, 36) provided with two electrical connections at two diametrically opposite points. The potential difference between these connections is proportional to the elastic wave transmitted or received by said membrane. A continuous polarization means of the magnetostrictive membrane is also provided. It comprises a high magnetic permeability part (40, 42), whose shape substantially corresponds to that of the membrane and which is placed in the vicinity of the latter, and a permanent magnet (38) in contact with said part.Application to the transmission of high frequency elastic waves in water (hydrophone) and to high fidelity sound reproduction in air.

Abstract: A ring-shell projector capable of simple disassembly and reassembly. The underwater transducer has a driving ring and a pair of flexible diaphragms on either side of the ring with their rims attached to the ring. The ring is formed of an array of electrostrictive elements and spacer elements, each spacer element having a pair of radial, outward extensions. A pair of coupling rings are provided each adapted to be positioned between the rim of one flexible diaphragm and a corresponding array of spacer element extensions to provide sealing engagement between the flexible diaphragms and the driving ring. Besides simplifying the repair of a projector, the improved design is more versatile, allowing a single driving ring to be used with different sets of shells, having different resonance frequencies and/or bandwidths. Moreover, an expensive step in the construction of a ring-shell projector is obviated, namely, the bolt holes in the metal staves and the subsequent custom matching of the shell holes.

Abstract: A marine seismic vibrator includes a housing having first and second housing portions defining an internal chamber therebetween. A hydraulic cylinder or other energizing device is connected between the first and second housing portions. The first and second housing portions are maintained in a spaced apart, non-contacting relationship. Relative motion between the first and second housing portions is provided by the hydraulic cylinder in order to generate acoustic waves in a surrounding body of water. An annular flexible seal construction is connected between the first and second housing portions for isolating the internal chamber from the surrounding body of water. This seal construction includes first and second flexible web portions sealingly connected to the first and second housing portions. A rigid hoop is connected between the first and second web portions for supporting the seal against pressure differentials between the internal chamber and the surrounding body of water.

Abstract: An electro-mechanical spring which provides amplified motion as well as a compliant structure for attachment, at the locations of maximum motion, to other mechanical or acoustical loads or elements. The spring produces motion in a directional orthogonal to the direction of a piezoelectric or magnetostrictive drive member connected along the major axis of a complete shell. The electro-mechanical spring provides a means for obtaining a low frequency large displacement piston type transducer.

Abstract: A microphone probe for acoustic measurement in turbulent flow. The probe includes a tube having a closed end facing upstream with respect to the direction of sound propagation, and a microphone is located in the downstream end of the tube. The tube is provided with a plurality of small ports, or alternately a slit, that extend a substantial portion of the length of the tube and an acoustically resistive material is stretched across the ports and clamped to the tube. In one form of the invention, the side edges of the material are connected to rigid bars and the bars are drawn together by a plurality of threaded fasteners to stretch the material over the ports. The threaded adjustment of the fasteners provides a means for varying the acoustical resistance of the material. In a second form of the invention, the bars to which the side edges of the material are attached, are clamped together by spring clips.

Abstract: An underwater acoustical transducer includes an annular, spring steel band supporting a diaphragm of a woven fabric held taut by the band. A flexible piezoelectric transducing element is attached with respect to the band, typically in contiguous relation to a portion of the fabric overlying the radially outward surface of the band. The transducing element can include an electrically conductive core surrounded by flexible piezoelectric material, or alternatively, a substantially flat strip of flexible piezoelectric material.

Abstract: Omnidirectional, wide pass band, elastic wave transducer comprising a rigid magnetostrictive diaphragm, each surface element of the diaphragm constituting a unidirectional elastic wave transducer in its normal direction, and an electric control means provided with two electric terminals for producing in the vicinity of the diaphragm a homogeneous magnetic field in keeping with an electric signal applied to the terminals of the control means or for supplying an electric signal in keeping with the variation of the magnetic field in the diaphragm as a function of an elastic wave received. The diaphragm is preferably a closed surface of revolution.Application in submarine transmission (hydrophone) and in high fidelity sound reproduction (loudspeaker, microphone) with a very wide pass band.

Abstract: A wide-range audio frequency underwater transducer is designed to make use of a massive small diameter vibratile piston driven by electromagnetic oscillatory forces to transmit omnidirectional uniform sound pressure level over the frequency range 100 Hz to 5 kHz. The rugged transducer design is adapted for low-cost mass production and can be used as a highly reliable expendable reference standard of source level for the calibration of in-situ stationary or moving sonar receiving systems. The magnitude of the source level can be accurately controlled by the magnitude of the electrical current supplied to the electrical winding over the entire frequency range of operation. A pressure equalization system is included in the design that permits use of the transducer at any depth down to 500 feet.

Abstract: An electromagnetically driven vibratile piston underwater transducer element generates acoustic intensity levels in excess of 25 peak Watts per square inch of radiating surface in the low audible frequency region within the approximate range 500 to 2500 Hz. The design achieves an efficiency greater than 50% and a very low Q of less than 2. The electromagnetic design employs two separate independent air gaps and a unique mechanical coupling system that combines the electromechanical forces generated in each gap in the proper phase and transmits the combined oscillatory force to drive the vibratile piston.

Abstract: Non-active columnar members are disposed on both sides of an active columnar member consisting of a piezoelectric ceramic material or a magnetically strainable material. Levers are connected to the active and non-active columnar members via first and second hinges. Convex shells are connected to the levers via third hinges. The displacement of the active columnar member is enlarged via the lever action, thereby enabling a miniaturized ultrasonic wave transmitter having high power capability.

Abstract: An arrangement in a piezoelectric hydrophone that is provided with a protective outer housing enveloping a waterproof closed casing (2). Said casing is provided with two mutually opposed and parallel diaphragm wafers (3) on the insides of which piezoelectric crystals (4) being metal coated on their outsides are respectively attached. A connecting wire is extended from said case through its hollow central portion (6). Said central portion (6) is formed by at least two ceramic elements (7) joined along a plane parallel with the diaphragm wafers and provided with a metalization (11) in the mutual contact areas (9, 10). In the cavities (12) respectively of the two elements (7) stiffening ceramic disks (8) are provided and attached to the elements (7) by the aid of a matching projection (13). The inward facing poles of the piezoelectric crystals are conductively connected with the metalization in the contact plane of the elements, and an additional wire (5) is provided from the metalization (11) on the outside.

Abstract: A pressure gradient sensor is disclosed for optically sensing the direction and magnitude of an acoustic wave propagating through a fluid. Each sensor consists generally of at least three fiber-optic displacement sensors disposed within a circular array oriented perpendicular to the longitudinal axis of a streamer. Each sensor phase-modulates a coherent light signal indicative of the water pressure sensed outside the streamer. The output of the signals include a component due to transient pressure waves and a component due to hydrostatic pressure differences between the sensors.

Abstract: An underwater transducer in which a ring of piezoelectric ceramic elements vibrates radially in response to an applied voltage. Spacer elements formed of steel are placed between pairs of ceramic elements and used to couple the ring movement to convex diaphragms. Each diaphragm is formed with radially extending fingers, which attach to the spacer elements. A water bladder assembly within the transducer forms a passive internal pressure compensation system. Preferably, the water bladder assembly is attached to the ring in a manner that mechanically decouples the bladder assembly from the ring.

Abstract: A pressure and temperature compensated acoustic transducer utilizing a pressure sensitive birefringent element coupled between a flexible diaphragm sealing the transducer and an internal variable rigid diaphragm that forms two internal chambers. Relatively rapid variation in pressure applied to the birefrigent element cause fluctuations in the phase difference between orthogonal components of a polarized light beam traversing the photo-elastic material. Detections of this phase difference variation provides signals representative of incident acoustic signals. Provision for the transfer of liquid filling the chambers permits the equalization between the two chambers of slowly varying internal pressures caused by changes in external ambient pressure and temperature.

Abstract: A seismic streamer section includes a flexible tube with bulkheads at intervals therealong, end means to make electrical and mechanical connections with adjacent sections, tension lines extending from one end means to the other through the bulkheads, hydrophones in the tube between the bulkheads, an electric bundle including through conductors extending from one end means to the other through the bulkheads to various ones of the hydrophone. Each hydrophone comprises a drum shaped case with dished ends and convex sides providing standoff from the bundle and lines for piezoelectric wafers supported inside the ends. A cylindrical metal ring forms the side of the case. Stainless steel cups disposed with their bottoms adjacent and having their rims welded to the rims of the ring form the ends of the case. The piezoelectric wafers are conductively secured one each to the inner surfaces of flexible diaphragms forming the bottoms of the cups.