Abstract: Disclosed is a design method for resisting a dynamic load in a high temperature pipeline. The method includes the following steps: a first calculation step, calculating to obtain a temperature deformation displacement of each point of the pipeline; a second calculation step, calculating to obtain a modal result of the pipeline and a dynamic response displacement of each point of the pipeline; a comprehensive analysis step, comprehensively analyzing the temperature deformation displacement and displacements of the vibration modes of respective orders of the pipeline to find a position at which a rigid constraint is required to be added, and applying the rigid constraint along a direction in which the temperature deformation displacement is not affected substantially; and a determination step, calculating a stress of the pipeline and a reaction force of the rigid constraint to determine whether the stress and the reaction force meet design requirements.

Abstract: An acoustic projector is provided with an enclosure having a semi-permeable membrane on one side. High salinity liquid is injected at the enclosure to increase osmotic pressure. Valves thereafter allow free flooding between the enclosure and surrounding seawater to equalize the pressure. Transient pressure in the enclosure generates a pressure pulse that propagates from the semi-permeable membrane. The timing of the injection by salt jets and the free-flooding valves enables a repeatable acoustic pulse at low frequencies and a determinable upper frequency. If the acoustic projector is mounted to be conformal to the hull of a ship; the acoustic projector includes a free-flowing region on one side of a semi-permeable membrane and valves. When the valves are opened; the other side of the membrane is free-flooded. Salt jets inject high salinity liquid into an enclosure to increase pressure with the result of an acoustic pressure pulse.

Abstract: An underwater acoustic projector for projecting acoustic energy through water is described. The acoustic projector includes a housing defining an internal cavity, a plurality of apertures in the housing that place the internal cavity in fluid communication with an external environment, an acoustic baffle disposed in the internal cavity at a first end that fluidly seals the first end of the internal cavity from the external environment, and a projector face that is disposed in the internal cavity at a second end of the internal cavity. The projector face includes a movable piston disposed between outer and inner diaphragms. A magnet is fixed within the internal cavity between the acoustic baffle and the projector face, and a moving coil is connected to the piston and arranged relative to the magnet so as to be driven by the magnet thereby driving the piston.

Abstract: A sensor is provided, with the sensor including a reflective element and an optical fiber positioned relative to the reflective element such that light emitted from the optical fiber is reflected by the reflective element and propagates in an optical cavity between the optical fiber and the reflective element. A first material is within the optical cavity and has a coefficient of thermal expansion and a thickness that compensate a refractive index change with temperature of a second material within the optical cavity.

Abstract: A oscillator in a liquid includes an actuator element oscillating in a reciprocating manner, and a sound-producing element attached to the actuator element, whereby the actuator element generates a motion in the sound-producing element for producing a sound. The oscillator is made open, whereby the pressure of liquid acts both on a first surface and on a second surface of the wall of the sound-producing element while the sound source is in the liquid. The material and/or structure of the wall of the sound-producing element is provided to be such that the distance between the first surface and the second surface of the wall varies as sound is produced.

Abstract: An external ultrasound probe assembly capable of scanning a three-dimensional volume is provided. The ultrasound probe assembly contains a plurality of ultrasonic transducers disposed along a longitudinal axis of the probe assembly. The plurality of ultrasonic transducers is disposed on a mechanism operable to reciprocally pivot the plurality of ultrasonic transducers enabling the plurality of ultrasonic transducers to scan the entire three-dimensional volume. A helically disposed electrical interconnection member may be disposed about a pivot axis of the plurality of ultrasonic transducers and may electrically interconnect the plurality of ultrasonic transducers to an ultrasound imaging system. The ultrasound probe assembly may be fluid filled and contain bubble position control and fluid expansion compensation features.

Abstract: The invention consists of an optical hydrophone, an optical fiber element forming a laser cavity, housed in a mechanical structure which comprises an open cylindrical rigid body, defining the cavity enclosing a fluid and in which the optical fiber element is housed, and closed at its ends by two end caps which keep the optical fiber element permanently under tension, in a longitudinal rectilinear position inside the cavity. The end caps are configured in such a way that when the exterior pressure varies, they undergo a deformation giving rise to a variation in the length of the optical fiber element and that when the temperature varies, they undergo a deformation giving rise to a variation in the length of the optical fiber element which compensates for that induced on this element by the temperature variation. The mechanical structure furthermore exhibits one or more orifices allowing equilibration of the static pressures.

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: The invention discloses a silicon-based monolithic integrated sonar array which includes a cantilevered sensing array structure, a sound-transparent jacket, and a support structure. The cantilevered sensing array structure is fixed on the support structure and in the sound-transparent jacket, wherein the sound-transparent jacket is filled with insulating dielectric oil, and the cantilevered sensing array structure is immersed in the insulating dielectric oil. The sound-transparent jacket is sealed and is treated with water tightness processing. The array can be applied, into devices for underwater ultrasonic imaging, ultrasonic ranging, torpedo navigating, etc.

Abstract: A seismic sensor unit includes a sensor housing including an inner chamber and a receiver extension for ground coupling, a suspension fluid disposed in the inner chamber, and a hydrophone suspended in the suspension fluid. The seismic sensor unit may include a sensor housing including a steel spike coupled to the ground, a fluid chamber in the sensor housing, a fluid in the fluid chamber, and a hydrophone disposed in the fluid chamber and contacting the fluid such as to detect a pressure wavefield in the fluid caused by ground motion acting on the steel spike. A method includes receiving ground motion at a seismic sensor unit coupled to the ground, transmitting the ground motion to a fluid chamber, creating a pressure wavefield in a fluid in the fluid chamber in response to the ground motion, and detecting the pressure wavefield in the fluid using a hydrophone.

Abstract: A vibrating element manufacturing method by which adhesion is stabilized and yield is improved, a vibrating element, a vibrating actuator, a lens barrel and a camera system. A vibrating element manufacturing method is provided with a first step of arranging an elastic body on a holding member, a second step of forming an electromechanical transducing element by injection molding on the surface of the elastic body, and a third step of sintering the electromechanical transducing element by heating and bonding the elastic body with the electromechanical transducer element.

Abstract: An acoustic source for use in a saltwater environment includes a transducer for projecting acoustic energy. The transducer is positioned within a semi-permeable membrane. The volume around the transducer within the membrane is filled with water having a lower concentration of a solute such as salt. When positioned in the saltwater environment, an osmotic pressure is created within the membrane. This osmotic pressure acts to suppress cavitation such as that which could be generated by the transducer. In further embodiments a support structure is used to support the membrane and the transducer could be an array of transducers.

Abstract: An acoustic mirror of alternately arranged layers of high and low acoustic impedances is manufactured in that a basic material having a first layer of the layer sequence is initially provided, on which a second layer of the layer sequence is created on the first layer such that the second layer of the layer sequence partially covers the first layer. Subsequently, a planarization layer is applied onto the layer sequence, and the planarization layer is removed in an area which in the common layer plane projects laterally beyond the second layer so as to result in a residual planarization layer. Finally, a termination layer is applied onto the layer sequence and the residual planarization layer.

Abstract: A fiber optic hydrophone has a reflective diaphragm having an exposed face and a reflective protected face, at least one transmitting multimode optical fiber having an end spaced apart from the protected face of the diaphragm positioned to emit light toward the diaphragm housing, and a reservoir. A cavity is defined by the diaphragm and the interior surface of the housing. Silicone oil and a compliant elastomeric material with embedded air bubbles are located in the cavity. Ports between the cavity and the reservoir and the reservoir and the exterior of the hydrophone allow static pressure communication between the cavity and the exterior of the hydrophone. The fiber optic probe can have one transmitting multimode optical fiber and six receiving multimode optical fibers, or more or fewer optical fibers. A grating can protect the diaphragm from environmental damage.

Abstract: The production of a hearing aid device can be simplified by the use of a microphone module with a plurality of microphones. To attach and electrically contact the microphones, the invention provides a microphone carrier with three-dimensionally directed conductor traces in MID technology. In a complicated microphone arrangement with a plurality of microphones, a single microphone module can thereby be used on which all microphones of the hearing aid device are attached and electrically connected.

Abstract: An oscillator device having an oscillating member, a resilient support and a supporting member is produced. The oscillating member is supported by the resilient support for oscillation about an oscillation axis. The oscillating member is formed with a movable element having protrusions for adjusting its mass, the protrusions extending from the movable element parallel to the oscillation axis and being formed in pairs disposed at positions symmetrical with respect to the oscillation axis. A sectional area of each protrusion along a plane perpendicular to the oscillation axis is constant in the oscillation axis direction. A laser beam is projected to a cutting position of protrusions, so as to partly remove the protrusion. The protrusions are cut based on adjusting the cutting position. The sum of the lengths removed from the protrusions by the cutting becomes equal to a predetermined length to thereby adjust an inertia moment of the oscillating member.

Abstract: Provided is a faceplate for an In-The-Ear (ITE) hearing aid and a method of manufacturing a faceplate for an In-The-Ear (ITE) hearing aid in which the faceplate can be manufactured in a compact size, using a foldable flexible printed circuit board (PCB), while maintaining the quality, enabling mass-production, and reducing the manufacturing cost.

Abstract: An acoustic mirror of alternately arranged layers of high and low acoustic impedances is manufactured in that a basic material having a first layer of the layer sequence is initially provided, on which a second layer of the layer sequence is created on the first layer such that the second layer of the layer sequence partially covers the first layer. Subsequently, a planarization layer is applied onto the layer sequence, and the planarization layer is removed in an area which in the common layer plane projects laterally beyond the second layer so as to result in a residual planarization layer. Finally, a termination layer is applied onto the layer sequence and the residual planarization layer.

Abstract: A method of making an acoustic assembly for use in a transducer includes forming a multi-layer assembly. The multi-layer assembly includes a first layer member and a second layer member. Each member includes a center portion, an edge portion and an aperture separating the center portion and the edge portion. The assembly has an assembly stiffness that is greater than the stiffness of either the first or second layer members. A hinge joins the assembled first and second center portions and the first and second edge portions such that the assembled first and second center portions is free to at least partially rotate relative to the assembled first and second edge portions about an axis. A flexible layer member is coupled to the assembly and provides airtight sealing of the passageway.

Abstract: The present invention relates to a vortex bubble removing and cooling system for the electromagnetic shock wave generator in the lithotripter. The vortex bubble-removing and cooling system comprises a water-full cushion (17), a metal diaphragm (14) installed inside the chamber body (27) of the water cushion (17) and a coil (13) which is installed at the backside of the metal diaphragm (14). There is at least one first water nozzle (22) on the side wall of the chamber body (27) and a water suction tube (23) at the center of the chamber body (27). The first water nozzle (22) and the water suction tube (23) form a vortex-generating device. The vortex generated inside the chamber body will scour the surface of the metal diaphragm continuously so as to cool the heat and remove the air bubble. This will make the metal diaphragm be in good working condition and greatly increase the working life of the metal diaphragm and the coil.

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: Reflective apparatus and method by which energy is radiated in divergent fashion from an elongated source and is reflected by a first parabolic reflector as a paraxial beam, focused by a second parabolic reflector onto a hyperbolic reflector and reflectively concentrated by the hyperbolic reflector at a focus at a distance from the source. The system also shields the point from extraneous radiation that would not be concentrated at the point. In one exemplary application, electromagnetic energy radiated from a point or linear source is focused by the multiple reflector system to a very high concentration at a point, for example, within an organism such as a human or animal body.

Abstract: Disclosed is a device for producing an intracorporeal pressure pulse comprising a pressure pulse source configured to generate a collimated pressure pulse and an acoustic lens including at least one ring-shaped focusing section configured to focus a pressure pulse generated by the pressure pulse source substantially to the vicinity of the central axis of the ring-shaped focusing section.

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 miniature lightweight transmitter that mechanically generates low-frequency acoustic energy is described, wherein one or more miniature balloons filled with air are positioned at the center of a pressure vessel filled with water and tethered in place. The system is then driven into resonance by using transducers that directly drive the wall of the pressure vessel or by using a piston to drive fluid into and out of the pressure vessel.

Abstract: In one embodiment the invention comprises a particle velocity sensor that includes a housing with a geophone mounted in the housing. A fluid that substantially surrounds the geophone is included within the housing. The particle velocity sensor has an acoustic impedance within the range of about 750,000 Newton seconds per cubic meter (Ns/m3) to about 3,000,000 Newton seconds per cubic meter (Ns/m3). In another embodiment the invention comprises method of geophysical exploration in which a seismic signal is generated in a body of water and detected with a plurality of co-located particle velocity sensors and pressure gradient sensors positioned within a seismic cable. The output signal of either or both of the particle velocity sensors or the pressure gradient sensors is modified to substantially equalize the output signals from the particle velocity sensors and the pressure gradient sensors. The output signals from particle velocity sensors and pressure gradient sensors are then combined.

Abstract: The present invention relates to a semiconductor electret condenser microphone capable of being reduced in size and including an acoustic sensor 100 and a case 200 for accommodating the acoustic sensor 100, the acoustic sensor 100 has a semiconductor chip 110 forming necessary electronic circuits 111A to 111C, and opening a through hole 112 away from the electronic circuits 111A to 111C, an electrode layer 120 formed on the surface of the semiconductor chip 110 away from the through hole 112, an electret member 130 laminated away from part of the electrode layer 120 and through hole 112, and a diaphragm 140 provided with a spacing 160 to the electret member 130, in which the electrode layer 120 exposed from the electret member 130 is connected to the electrode 111a of the electronic circuit 111A through the case 200 (FIG. 6).

Abstract: The present invention relates to a semiconductor electret condenser microphone capable of being reduced in size and including an acoustic sensor 100 and a case 200 for accommodating the acoustic sensor 100, the acoustic sensor 100 has a semiconductor chip 110 forming necessary electronic circuits 111A to 111C, and opening a through hole 112 away from the electronic circuits 111A to 111C, an electrode layer 120 formed on the surface of the semiconductor chip 110 away from the through hole 112, an electret member 130 laminated away from part of the electrode layer 120 and through hole 112, and a diaphragm 140 provided with a spacing 160 to the electret member 130, in which the electrode layer 120 exposed from the electret member 130 is connected to the electrode 111a of the electronic circuit 111A through the case 200 (FIG. 6).

Abstract: A non-explosive acoustic source utilizes the combustion of aluminum and water to generate an acoustic pulse. The operation of the non-explosive acoustic source relies on a water/aluminum reaction to generate a burst pressure. The source may be deployed as a single charge or as one element of a multiple charge array and is configurable to explode at variable depths with variable energy levels. The inherent safety of the non-explosive acoustic source obviates the necessity for auxiliary safety features or procedures to protect against inadvertent explosion. As a result, the non-explosive acoustic source facilitates the implementation of sonic detection systems and reduces the operational costs associated with such systems.

Abstract: A surface acoustic wave device includes a piezoelectric substrate and at least one interdigital electrode disposed on the piezoelectric substrate. The interdigital electrode is made of ?-tantalum.

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: An underwater sound source which comprises a housing having an inner and an outer surface and a monopole driver suspended within the center of the housing. The housing is adapted to receive fluid therein to form a fluid column inside the housing. The underwater sound source resonates at a frequency of 260 Hz when the monopole driver excites the fluid column.

Abstract: A pressure-pulse therapy apparatus, including a dome-shaped reflector, at least one ring section, a central x-axis, an open end, a flexible diaphragm capping the open end, a fluid medium within the reflector and diaphragm, a pressure-pulse source immersed in the fluid medium and located on the x-axis for generating a primary pressure pulse, and a power supply for the pressure-pulse source. The reflector includes a center section that has a predetermined first curvature and associated reflective characteristics to reflect the primary pressure pulse to form a first subordinate pressure pulse of a compound pressure pulse. The ring section is substantially concentric with the center section and has a predetermined second curvature and associated reflective characteristics to reflect the primary pressure pulse to form at least one additional subordinate pressure pulse of the compound pressure pulse.

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: 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 method and device for generating a high amplitude sound wave is provided. The device includes a housing having an open end. A piston is slidably disposed in the open end of the housing and forms a chamber for holding a pressurized liquid. The pressurized liquid acts on the piston to move the piston relative to the housing. A latch is operable to fix the piston relative to the housing and to release the piston. Upon release of the latch, the piston moves relative to the housing to generate the sound wave. In the method of the present invention, a piston is fixed relative to a housing to form a chamber between the housing and the piston. The chamber is filled with a pressurized fluid and the piston is released to allow the pressurized fluid move the piston relative to the housing and generate the sound wave.

Abstract: Acoustic intensity is measured by a submerged probe consisting of two passive geophones mounted in spaced relationship with their sensing axes aligned. The geophones are connected through a cable to a remote spectrum analyzer in which acoustic intensity is computed from the velocity gradient between the two geophones. The exclusive use of geophones, which inherently have low impedance outputs, eliminates the need for preamplification in the probe. The geophones are mounted inside an acoustically transparent, thin rubber shell, which reduces the effects of noise due to flow.

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 chain of elongate components (10, 20) are connected end-to-end. Each component (e.g. 10) comprises a sheath (1) closed at its ends filled with a dielectric liquid (e.g. kerosene). Sound detectors are located in the liquid as are electric conductors for conveying signals therefrom. The ends are closed by means including an electric connector. At least one of a pair of mating end portions includes a valve (14, 24) which releases the dielectric liquid from inside the sheath into the interstices between the mated pair. A bleed screw can be used to ensure no air remains. This arrangement minimises pressure differentials around the join between two adjacent elongate components and facilitates use of the chain at great depths.

Abstract: An ultrasound probe housing has at least one air bubble trap disposed therein and configured to facilitate movement of air bubbles away from a window thereof and also configured to resist movement of the air bubbles back toward the window. Preferably, two air bubble traps are utilized, one proximate the ultrasound transducer and the other proximate the motor thereof, so as to facilitate isolation of the ultrasound transducer and motor from air bubbles. The air bubble traps are preferably configured as funnels having a narrow end thereof oriented away from the window and having a wide end thereof oriented toward the window such that air bubbles easily enter the wide end thereof but do not easily enter the narrow end thereof. The air bubbles preferably move to a fluid expansion compensation chamber wherein they become captured and provide compensation for thermal expansion of the ultrasound transmissive fluid contained within the ultrasound probe.

Abstract: A transducer includes one or more electro-acoustic motors located on a same internal plane or as a peripheral ring of a flexible envelope to which they are interdependent by at least one-of their ends by an assembling device and to which they transmit their vibrations, the flexible envelope being in contact with the liquid and constituting the acoustic waves emitting surface. The flexible envelope is shaped such that the amplitude of the vibrations is increased in a range of very low frequency. The envelope includes at least one orifice allowing the liquid to enter the whole internal cavity delimited by the envelope and a baffle made up of alveolar material that resists the immersion pressure and fills most of the cavity volume. The external surface of the baffle is at a constant distance from that of the interior of the envelope and is interdependent to the assembling device of the acoustic motors.

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

Abstract: An acoustic 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: 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: 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: In the underwater sound source disclosed herein, rigid diaphragms are provided at opposed ends of a hollow shell, the periphery of each of the diaphragms being sealed to the shell. Respective spring means operating between the shell and each of the diaphragms allows axial displacement of the diaphragm in response to external pressure. A lightweight magnetic armature structure is connected to each of the diaphragms and opposed electromagnetic core structures provide magnetic circuits which link each of the armature structures across respective gaps. Further spring means are provided for centering each of the armature structures between the respective magnetic core structures. By appropriately energizing windings on the magnetic core structures, the armatures together with their respective diaphragms are caused to oscillate.

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: 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: There is disclosed, a piezoelectric transducer for generating focussed ultrasonic shock waves for use in lithotripsy. The ultrasonic shock waves are emitted in pulsed form and can be transmitted by way of a coupling medium to the body of a patient to be treated. The transducer comprises a substantial member of individual piezoelectric transducer elements of ceramic or like material which are connected to the poles of a pulse generator and are fixed to a support in mosaic form and with their sides electrically insulated from one another. The acoustic termination of the transducer elements is essentially free from reflection. An intermediate medium of at least one layer, the acoustic impedance of which lies between that of the ceramic of the transducer element and that of the coupling medium, is provided between the transducer elements and the coupling medium. The thickness d of the layer is chosen in accordance with the relationship d>.tau..sub.k .multidot.c.sub.LA, where .tau..sub.