Abstract: Aquatic organism tracking devices, systems and associated methods are described.

Abstract: A hydrophone free from internal leads and further including a stabilizing jacket is described. The hydrophone uses the metallic end caps of the stabilizing jacket to complete the circuit thereby eliminating the need for internal leads. Further, the stabilizing jacket results in a hydrophone configuration that can withstand harsher conditions while nonetheless providing excellent detection capabilities.

Abstract: A disclosed data acquisition system includes one or more streamers having multiple spaced apart sensor units. At least one sensor unit includes at least one digital sensor employing a quantized feedback loop to produce a digital output signal. A data recording system collects and stores data from the sensor units. The quantized feedback loop may be adapted to exert a quantized force on the sensing element. A described method for acquiring data includes deploying at least one streamer having multiple spaced apart sensor units, where at least a portion of the sensor units include a digital sensor employing a quantized feedback loop to produce a digital output signal. A stimulus event is triggered. Data is received from the sensor units and stored.

Abstract: Sensors used in mapping strata beneath a marine body are described, such as in a flexible neutrally buoyant towed array. A first sensor is a motion sensor including a conductive liquid in a chamber between a rigid tube and a piezoelectric motion film circumferentially wrapped about the tube. The liquid transfer signal from a gravitational bottom of the sensor while rejecting water body surface reflected noise. A second sensor is a traditional acoustic sensor or a novel acoustic sensor using a piezoelectric sensor mounted with a thin film separation layer of flexible microspheres on a rigid substrate. Combinations of motion sensors and acoustic sensors co-located in a rigid streamer housing sections are provided.

Abstract: One aspect provides a method including determining that an absolute pressure sensor is not submersed in a fluid; measuring an atmospheric pressure with the absolute pressure sensor to determine an offset pressure measurement; submersing the absolute pressure sensor in a fluid; and measuring pressure with the absolute pressure sensor; wherein a compensated pressure measurement of the fluid is determined. Other embodiments are disclosed.

Abstract: Seismic wave sources and related methods are provided. A seismic wave source includes a housing, plural pillars and an excitation system. The housing is split in two halves along a plane including a longitudinal axis of the housing. The plural pillars are made of piezoelectric elements and are positioned inside the housing to have one end in contact with a semi-cylindrical middle portion of one half of the housing and another end in contact with a semi-cylindrical middle portion of the other half of the housing. The excitation system connected by wires to the plural pillars and is configured to provide electrical signals to the piezoelectric elements. Upon receiving the electrical signals from the excitation system, the pillars generate forces on the housing thereby generating seismic waves.

Abstract: An acoustic source for generating an acoustic beam includes a housing; a plurality of spaced apart piezo-electric layers disposed within the housing; and a non-linear medium filling between the plurality of layers. Each of the plurality of piezoelectric layers is configured to generate an acoustic wave. The non-linear medium and the plurality of piezo-electric material layers have a matching impedance so as to enhance a transmission of the acoustic wave generated by each of plurality of layers through the remaining plurality of layers.

Abstract: An electroacoustic transducer submersible in an immersion fluid (8) for underwater acoustic communications, includes two horns (3a, 3b), a counterweight (4), two electroacoustic motors (1a, 1b), aligned along an axis of symmetry (6), the opposite ends of the motors being respectively connected to a horn, the unit consisted by the electroacoustic motors, the counterweight and the horns being able to generate a longitudinal electroacoustic resonance mode. The transducer includes a rigid and hollow cylindrical part (5) extending around the counterweight, the cylindrical part having an axis merged with the symmetry axis of the transducer, the inside of the cylindrical part forming a fluid cavity able to be filled with the immersion fluid, the electroacoustic motors and the cylindrical part being so dimensioned that the fluid cavity forms an acoustic coupling between the longitudinal electroacoustic resonance mode and a circumferential resonance mode of the cylindrical part.

Abstract: An electronic apparatus includes a substrate and an oscillation device (100) which is supported over the substrate, wherein the oscillation device (100) includes a piezoelectric element (110), a vibrating member (120) which binds one surface of the piezoelectric element (110), and a tubular support member (140) which supports an outer edge portion of the vibrating member (120) in an inner surface and is joined to the substrate so that an opening of one end side is closed by the substrate, and the support member (140) includes at least one hole (141) which connects a space, which is surrounded by the substrate and the vibrating member (120) in an inner portion of the support member (140), to an outer portion of the support member (140).

Abstract: A hydrophone unit comprising a resilient central wire; a conductive wire coiled around the resilient central wire, said conductive wire being coated with a piezo material for generating an electrical signal in response to the presence of an acoustic vibration, wherein the resilient central wire is fabricated from spring steel, the conductive wire is a copper wire, the piezo material includes polyvinylidene difluoride; a layer of conductive material deposited on the piezo material-coated conductive wire, wherein the layer of conductive material comprises a silver ink; and a jacket of polyurethane.

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

Abstract: A slotted cylinder acoustic transducer has a crescent-shaped insert disposed between a ceramic stack assembly and s cylindrical housing shell. In some embodiments, all of the ceramic elements in the ceramic stack assembly can have the same shape.

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

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

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

Abstract: A longitudinally segmented acoustic transducer for a cement bond logging (CBL) tool having a plurality of adjoining PZT ring-like segments driven synchronously in parallel by one or more pulses and caused to vibrate in an anti-resonant mode, substantially below the resonant frequency of an individual segment when used in a transmitting application. When used in a receiving application, each of the plurality of transducer rings are caused to vibrate by acoustic signals detected by the transducer array, also in an anti-resonant mode. High speed digital signal processing enables on-depth, high quality data for all azimuths at each depth to be obtained, processed, normalized and either sent to the surface in real time for each 20 Hz firing cycle, as the CBL tool is pulled toward the surface, or stored in a memory module in digital form for later retrieval. Built-in calibration factors used for normalizing the output signals to the operating conditions of use may be accessed at any time.

Abstract: Various sensors use an electro-active device (11) electrically connected to a detector circuit. The electro-active device (11) comprises an electro-active structure in the form of a continuous electro-active member (12) curving in a helix around a minor axis (13) which is in itself curved for example in a helix around a major axis (14). On activation by relative displacement of the ends (16) of the device (11), the electro-active structure twists around the minor axis due to the fact that the minor axis (13) is curved. The continuous member (12) has a bender construction of a plurality of layers (21) and (22) including at least one layer of electro-active material so that concomitantly with the twisting the continuous member (12) bends generating an electrical signal detected by the detector circuit. The electro-active device (11) is advantageous as a sensing element in a sensor because it has a large displacement, high sensitivity and low compliance.

Abstract: A seismometer having a hydrodynamically efficient shaped body containing a seismic sensor or source, having a propulsion unit located and a control unit for directional control of the propulsion unit for guiding the seismometer to and from an ocean floor. The seismometer can be deployed from a surface ship, helicopter or airplane. The seismometer or surface support vessel contains a navigation unit for directing the control unit to a desired location on the ocean bottom. The apparatus provides a storage device for storing seismic data sensed by the seismic sensor. The navigation system sends a responsive directional command to the apparatus based on the current location and the desired location. Upon arrival at the desired ocean bottom location, the propulsion system acts to couple the apparatus to the ocean floor. A flight control system manages a plurality of the seismometers during navigation to and from the a ocean bottom.

Abstract: A plurality of heavy mass irregularities attached to an inner wall of the drill collar attenuate waves traveling through the collar. The plurality of heavy mass irregularities are spaced and sized for the maximum attenuation of acoustic pulses in a predetermined frequency range. The mass irregularities may be rings firmly coupled to the outer surface of the collar. Alternatively, the mass irregularities may be rings firmly coupled to the outer collar surface by neck pieces, extending inwardly from the inner circumference of the ring. The mass irregularities may be made of steel or tungsten. In another preferred embodiment, the mass irregularities are asymmetrically coupled to an outer collar wall for providing preferential directional attenuation.

Abstract: A multi-port projector of acoustic energy in water includes a cylindrical hollow transducer having open annular ends. A thin, flexible member is secured to each annular end to extend across each opening to be displaced by the transducer, and the transducer and flexible members form an interior sealed from ambient water. A battery/electronics module is in the interior and is spaced from the transducer and flexible members to couple driving signals to the transducer for reciprocally displacing it and the flexible members in response to the driving signals. An inert liquid fills the interior around the module, and an open truss on each annular end exposes the flexible members to the ambient water. Cylindrical portions coaxially extending with the transducer on a common longitudinal axis are connected to the open trusses for projecting acoustic energy of lower frequency than conventional cylindrical transducers of similar size.

Abstract: A sleeve for an acoustic logging tool has a structure with a window section having fewer bars than a conventional sleeve separated by a slotted region with thin circumferential slots which are stress-relieved at the ends (“dumb-bell” shaped). Steel receiver mounts are provided for hydrophone pressure sensors and this, together with the axially oriented hydrophones makes the tool less susceptible to interfering vibration.

Abstract: A system for detecting source acoustic energy in seismic operations. The system is operable on land and in marine applications. On land, a piezoelectric film is positioned between a vibrator or other source baseplate and the soil. Compression of the piezoelectric film generates an electrical signal proportional to the total ground force, including force due to flexural or resonance of source components, exerted by the seismic source. In marine applications, a source displaces water to produce a pressure pulse in the water, and a piezoelectric film detects the resulting pressure pulse and the flexural movement of the source to produce an electrical signal proportional to the movement of the active component.

Abstract: A method of marine seismic surveying, whereby a seismic streamer is towed in a body of water while deploying three (3) sensors in close proximity to each other. In one embodiment of the invention, the first sensor generates a first signal indicative of pressure of the water, the second sensor generates a second signal indicative of vertical movement of water, and the third sensor generates a third signal indicative of vertical movement of the streamer relative to the water. A seismic signal is generated in the water and the resulting signal is detected with each of the three (3) sensors simultaneously during time intervals following the generation of the seismic signal. The second signal is combined with the third signal to generate a fourth signal that measures vertical movement of the water with noise due to streamer vibration attenuated. The first signal is combined with the fourth signal to give a signal that attenuates the ghost due to the water surface.

Abstract: The present invention relates to an electromechanical converter, a method of manufacturing same, as well as to a composite system including the electromechanical converter. The inventive electromechanical converter consists of at least one elongate fiber (1) made of a piezoelectric material. At least two electrodes (2) are provided at mutually spaced locations on the fiber (1) for subjecting the fiber to an electrical field. The electrodes (2) are in direct contact with the fiber (1) and enclose the fiber (1) partly or completely. The direct contact between the electrode and the fiber permits the optimum introduction of the electrical field into the fiber such that lower electrical potentials on the electrodes are sufficient for polarising the fiber. Another advantage resides in the aspect that the electrode is in direct contact with the fiber not only at one point but over part of the periphery of the fiber. This results in a further enhancement of the introduction of the electrical field.

Abstract: A sealed slotted cylinder includes an active transducer assembly, end caps at each end of the assembly, and a boot fused to the end caps and sealing the assembly. The sealed slotted cylinder is made using a dummy insert and a spacer within the dummy insert for spacing the end caps. A boot material made from an uncured rubber is wrapped around the dummy insert and the end caps. This assembly is placed in a mold that fuses the boot material to the end caps by vulcanizing the uncured rubber material. The mold and dummy insert preferably form longitudinal and circumferential boot roll seals on the boot material. A section of the boot is then removed forming an open region, allowing the dummy insert and spacer to be removed. The active transducer assembly can then be inserted through the open region such that the longitudinal boot roll seal engages and seals the slot in the active transducer assembly and the circumferential boot roll seals engage the end of the active transducer assembly.

Abstract: An improved transducer arrangement for low frequency sonar projectors that convert electric signals to mechanically generated acoustic signals. In one embodiment the arrangement has both a convex flextensional transducer and a concave flextensional transducer. An open side of the convex transducer is attached to an open side of the concave transducer by an intermediate bulkhead which closes each of the attached open sides. An end plate is attached to another open side of the convex transducer and another end plate is attached to another open side of the concave transducer such that the end plates close the attached open sides. In another embodiment, transducer assembly has a convex transducer having end plates and a concave transducer having end plates. Either one of the endplates of the concave transducer is attached to one of the endplates of the convex transducer, or an endplate of the concave transducer is also an endplate of the concave transducer.

Abstract: A wide bandwidth, ultrasonic transducer to generate nondispersive, extensional, pulsed acoustic pressure waves into concrete reinforced rods and tendons. The wave propagation distance is limited to double the length of the rod. The transducer acoustic impedance is matched to the rod impedance for maximum transfer of acoustic energy. The efficiency of the transducer is approximately 60 percent, depending upon the type of active elements used in the transducer. The transducer input energy is, for example, approximately 1 mJ. Ultrasonic reflections will occur at points along the rod where there are changes of one percent of a wavelength in the rod diameter. A reduction in the rod diameter will reflect a phase reversed echo, as compared with the reflection from an incremental increase in diameter. Echo signal processing of the stored waveform permits a reconstruction of those echoes into an image of the rod.

Abstract: There is provided an acoustic source especially for use in seismic studies at sea. The acoustic source has a longitudinal axis and sound emitting surfaces adapted to be put into sound emitting movements towards and away from each other by use of a drive unit. The sound emitting surfaces comprise two curved plate members having upper and lower ends essentially symmetrically positioned in relation to the longitudinal axis of the acoustic source, and forming a convex cross section with their respective upper and lower edges converging towards each other. The upper and lower edges of the sound emitting surfaces, respectively, are connected to each other with two corresponding side elements, the side elements each being connected to at least one hinge stretching along at least a part of the length of the source.

Abstract: A marine seismic source for generating acoustic source energy from electrical power. A slotted housing has an exterior surface engaged with an electrically activated transducer such as a piezoelectric transducer. One or more piezoelectric components can be adhered or otherwise attached to the exterior surface of the housing. A case can cover all or part of the piezoelectric components, and the case can be waterproof to prevent contact between the transducer and the water. The case can be integrated with the slotted housing to form a composite structure, or a cavity, for containing a transducer such as piezoelectric components.

Abstract: Acoustic source, especially for use in seismic studies at sea, with sound emitting surfaces adapted to be put into sound emitting movements toward and away from each other by use of a drive unit in a known manner, in which the sound emitting surfaces comprise two curved plate members essentially symmetrically positioned in relation to the longitudinal axis of the source, forming a convex cross section with their respective upper and lower edges converging towards each other, and the respective upper and lower edges of the sound emitting surfaces are flexibly connected to two corresponding side elements positioned between them, and that the source comprises a rigid frame for supporting the drive unit, comprising at least two rigid slide rods stretching through the side elements, and that rigid covers are mounted on the slide rods, covering at least the whole side elements, thus forming rigid, covering surfaces with a constant distance between the covers.

Abstract: A seismic method and system for generating seismic source energy in marine geophysical operations. A slotted housing is moveable by the actuation of piezoelectric elements to generate high power, low frequency seismic source signals. When the piezoelectric elements are activated by electric power, displacement of such elements is enlarged by the slotted housing to generate a pressure pulse in the water. The invention permits single source pressure pulse generation having sufficient power and low frequency. The housing can be towed by a seismic vessel or can be integrated into a self-contained marine vehicle.

Abstract: A low-profile hydrophone module for a marine seismic system includes a block having a curved surface and a receiving surface in which an open cavity is disposed, a hydrophone assembly, to which lead wires attach, disposed in the cavity, lead wires which pass out of the cavity, and a sound-transmitting material which fills the cavity. In another feature, the hydrophone assembly includes a hydrophone and a baffle material, the baffle material enclosing the hydrophone, the cavity is sealed around the lead wires, the sound-transmitting material is oil, and a cover sealingly affixes over the cavity. In another feature, the hydrophone assembly includes a hydrophone and a frame, the cavity is sealed around the lead wires, the sound-transmitting material is a potting sealant, and a cover sealingly affixes over the cavity.

Abstract: The invention relates to underwater acoustic transmitters intended to be submerged at large depths. It consists in threading the set of annuli forming the transmitter onto an internal tube (303) preferably made from a carbon/resin composite, which supports two end plugs (306, 307) making it possible to relieve the set of annuli of the radial component of the hydrostatic pressure. Furthermore, between the piezoelectric annuli (101) of the transmitter are inserted decoupling annuli (301) which are made as a three-layer structure including a hard and rigid internal layer (201) and two flexible and elastic external layers (202, 203). It makes it possible to increase the transmitting power of these acoustic transmitters.

Abstract: A transducer array is constructed from a constant arc length portion of a ght circular cylindrical shell of piezoelectric transduction material. The constant arc length portion is segmented evenly along the length thereof to define a plurality of transducers. The transducers can be in the free field or mounted on a planar baffle.

Abstract: A piezoelectric transducer hydrophone comprised of a plurality of longitudinal segments is described. The longitudinal segments allow the transducers to be readily attached to cables to form hydrophone arrays. Should a particular transducer become faulty following testing or use of the hydrophone array, the longitudinal segments allow the transducer to be accessed without the need to remove all of the acoustic transducers on the cable between the end of the cable and the one that is faulty.

Abstract: A sound or ultrasound sensor is provided for transmitting and/or receiving sound or ultrasound, which is mechanically robust and chemically resistant and which has an adjustable emission characteristic, for example having a preferably small beam angle, having an emitting element (3) which has a flat front surface (34), and having a transducer element (1), the transducer element (1) causing the front surface (34) to oscillate on the basis of an excitation frequency, such that the entire front surface (34) carries out virtually in-phase deflections with virtually equal amplitude parallel to the normal to the front surface (34), and in which sensor concentric webs (32) are arranged on the front surface, there being a concentric gap (33) in each case between two adjacent webs (32), and a disk (5) sealing the sound or ultrasound sensor flush at the front, which disk is firmly connected to the webs (32) and has segments which are not connected to the webs (32) and are used as membranes (51).

Abstract: A liquid is subjected to ultrasound within a stainless steel pipe (35) of wall thickness 2.5 mm. Three ultrasonic transducers (56) are equally spaced around the pipe, each fixed to one end of a tapered resonant coupler (46) with a nodal flange (48) by which it is supported with its wider end coaxially within a steel collar (38) welded to the outside of the pipe wall. The space around the sides and the end of the coupler is filled by a buffer liquid such as olive oil. When the transducers (56) are energised they resonate, as do the couplers (46), and ultrasound is transmitted through the buffer liquid and the wall into the liquid inside the pipe (35). Within the pipe the intensity can be sufficient to cause cavitation, and so to cause sonochemical effects.

Abstract: The present invention relates to a process and transducer for emitting wide and and low frequency acoustic waves in unlimited immersion depth.The invention is applied to tranducers comprising at least one electro-acoustic motor (1) causing any wall 3 of the said waves to vibrate, and a hollow shell 5 enclosing the said motor 1, and delimiting with the said vibrating wall 3 among others, a cavity 7, characterised in that:at least one opening 5, causing cavity 7 to communicate with ambient medium 4, is made in said shell 5;in at least part of the volume of the said cavity 7, at least one flexible bladder 7, is installed;this bladder 8 is filled with a fluid 9 more compressible than fluid 4.

Abstract: A composite hydrophone array assembly is made from a compliant mandrel such s a hollow tube and at least one wrap of piezoelectric film adhered to the compliant hollow tube at a plurality of locations thereon. Each location defines a composite hydrophone channel. The centers of adjacent hydrophone channels are separated along the length of the compliant hollow tube. To shade a hydrophone channel, the wall thickness of the hollow tube can be varied along its length, the circumferential area of coverage of the wraps of piezoelectric film can be varied along their length, the longitudinal lengths of the wraps of piezoelectric film are varied, or a combination of these approaches can be used. Unwanted noise is rejected by eliminating hydrophone channel grating lobes and overlapping portions of the wraps of piezoelectric film of the adjacent hydrophone channels to create a wavenumber response for the composite hydrophone array that significantly reduces array grating lobes.

Abstract: The invention relates to directional electro-acoustic transducers compris a sealed shell consisting of two portions.A transducer according to the invention comprises one or more electro-acoustic drivers (1) composed for example of a stack of piezoelectric plates (1a, 1b, . . . 1n) located inside a sealed shell. This shell comprises a first portion (3A) symmetrical as to a plane (PP') fitted with two flanges at its ends, these flanges being coupled mechanically and acoustically by means of a rod (7) and two bolts (8) With each driver (1). The shell includes a second portion (3b) which is complementary to the first portion and which is acoustically uncoupled from the first portion and from the drivers.An application of the invention is the construction of low-frequency transmitter of acoustic waves in the water in a given direction.

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

Abstract: A transducer includes at least one cylindrical driving assembly and at least one headmass coupled to an end of the cylindrical driving assembly. The headmass has an external ring that surrounds a core. The core is made from a core material that is less dense than the material from which the external ring is made. The headmass is dimensioned to occupy a predetermined volume so as to transmit waves within a predetermined frequency range. As a result, the transducer provides higher power waves, yet occupies the same volume as the transducers of the prior art.

Abstract: An acoustic transducer comprises two pairs of opposite elongate segments (20) placed inside a deformable tube (14). Drive means (22) operable to expand in a direction orthogonal to the axis of the tube are disposed between the segments of each pair. The drive means occupy a substantial portion of the inside volume of the tube. A preferred arrangement includes drive means for a pair of segments longitudinally displaced from the drive means for the other pair. Drive means may be constituted by stacks of piezoelectric pellets (24) extending radially relative to the axis of the tube. A pressure compensation system is provided to keep the pressure inside the tube (14) substantially equal to the external pressure. Longitudinal flutes (14a) are formed inside the tube (14) between the segments (20) to facilitate tube deformation and amplify volume variation.

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

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

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

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

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

Abstract: A low frequency torsional transducer for the generation and/or reception of shear waves in a substantially solid medium. The transducer includes a spool like radiating structure to which are fixedly attached spaced piezoelectric elements. The elements undergo shear movement upon being electrically excited or upon receiving shear waves. This shear movement causes the opposite ends of the radiating structure to move torsionally. The torsional movement causes radiation of shear waves which can be detected by a sensor and used to determine the degree of support for shear wave propagation in the media.

Abstract: A support member preferably made of a metal such as cold rolled steel is disposed in a looped configuration and is provided with a gap. A transducer member preferably made of a piezoelectric material such as a ceramic is disposed within the support member. The transducer member is provided with a gap at a position corresponding to the gap in the support member. A closure member made from a suitable springlike material such as an alloy steel is attached to the opposite ends of the support member at the position of the gap as by welding. The closure member extends in a U-shaped configuration into the looped configuration (in section) defined by the support member and the ceramic member. The axial length of the closure member defines the bandwidth of the frequency vibrations generated by the transducer member.