Abstract: The present invention relates to a pressure regulator and in particular to a closed active pressure regulator gas coupled to an acoustic device which is disposed underwater. The pressure regulator comprising an internal pressure sensor, a valve, and a gas supply each coupled to a processor, at least said valve, gas supply and processor disposed within a fluid tight housing, said pressure regulator including an external pressure sensor coupled to the processor though the housing, whereby said pressure regulator is gas coupled to an acoustic device disposed underwater, said acoustic device contained within a pressure sealed and fluid tight container, said pressure regulator is a closed active system for removing gas from the container to the gas supply or supplying the gas from the gas supply to the container thereby regulating the pressure in the container.

Abstract: A transducer assembly including a rigid transducer housing. The transducer housing has an interior space and defines a transducer socket and a pressure balancing cylinder. A transducer device is fixedly mounted within the transducer socket. A pressure balancing piston is reciprocably mounted within the pressure balancing cylinder. A pressure balancing fluid and an electronics assembly are contained within the interior space. The electronics assembly is operatively connected with the transducer device. A measurement tool including a tool body and one or more transducer assemblies. The tool body defines one or more pressure balancing body passages extending between mounting pockets in the tool body. The transducer housings define one or more pressure balancing housing passages extending between the interior space and the exterior of the transducer housings. At least some pressure balancing body passages and some pressure balancing housing passages are in pressure communication with each other.

Abstract: A waterproof speaker module may include a membrane formed from at least one waterproof and elastic material and a supporting structure. The membrane may include an outer surface, an inner surface, and at least one concave region that is indented toward the inner surface. The supporting structure may be coupled to the membrane and include a support structure that mates with the concave region of the membrane when the speaker is subjected to a hydrostatic load. When the speaker is not subjected to a hydrostatic load, the support structure may contact the concave region. In this way, the membrane may be resistant to tearing or rupture due to hydrostatic load.

Abstract: An apparatus is provided for underwater operation comprising a pressure regulator configured to reduce a pressure of a gas received from a gas source at a first pressure to a second, lower pressure. A multiport differential pressure regulator is provided to receive the gas at the second pressure at a first port and to provide the gas to a second port at a differential pressure relative to an ambient pressure that varies based on a depth of the apparatus, where the differential pressure is set to a pressure that is at least 0.1 PSI below ambient pressure. A check valve vent is coupled to the second port of the multiport differential pressure regulator to relieve pressure at the second port accumulated by the apparatus during operation at a higher pressure depth when the apparatus rises from the higher pressure depth to a lower pressure depth.

Abstract: A rope-tension system for a marine seismic cable comprising a series of sensor nodes connected between flexible cable sections connected to other sensor nodes and flexible sections by armored cable segments. The flexible sections, which are housed in flexible protective covers, have a pair of ropes as stress members. The two ropes are pivotably pinned at both ends to termination units at the opposite ends of the flexible sections. The two ropes extend through a ring positioned between the two termination units. The pivots at the rope ends form linkages with the ropes that allow the ropes to adjust their positions as the flexible section engages a curved surface during retrieval. The ring presents bearing surfaces with a large radius of curvature to the ropes to avoid sharp bending loads.

Abstract: The invention relates to a hydrophone housing. The housing comprises an outer casing with an exterior shape being in close contact with sediment when buried therein and having a deflectable wall part. Solid material partly fills the casing to define an outer chamber behind the deflectable wall part, a cavity shaped so that an inner chamber is defined immediately surrounding a hydrophone sensing element held therein, and a first duct for liquid flow communication between the outer chamber and the cavity or an internal volume of the hydrophone sensing element. Thereby, a hydraulic coupling is provided so that an acoustic pressure causing small radial displacements of outer surface of the housing will, via liquid in the first duct, cause large radial displacements of the hydrophone sensitive element.

Abstract: An ultrasonic emitter comprises a support member operable to support an ultrasonic emittive material. The support member includes a plurality of support ribs. The ultrasonic emittive material is coupled to upper portions of the support ribs so as to be carried by the support member. A protective screen has a plurality of apertures formed therein, the protective screen being in contact with the ultrasonic emittive material atop the support ribs such that the spacing between the ultrasonic emittive material and the protective screen is substantially zero atop the support ribs.

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

Abstract: A marine vibratory sound source for producing swept or pulse coded signals in a body of water and within geological structures beneath a body of water, primarily for seismic exploration of the strata beneath the bottom of the water. More particularly, a high power, servo controlled hydraulic, sound source that can readily be towed in water, towed along the bottom surface under the water or be used in a stationary position on the bottom surface under the water.

Abstract: An electro-dynamic acoustic projector provides a rigid enclosure having an open end. A pressure compensated chamber extends into the rigid enclosure from the open end. A vibratile piston is located in the open end of the rigid enclosure and closed the pressure compensated chamber. The vibratile piston has an axis of oscillation perpendicular to the plane of the open end and an anterior major surface exposed from the open end for generating sound waves in water. A magnet assembly is attached to the vibratile piston which interacts with a stator coil positioned with respect the rigid enclosure and vibratile piston. The magnet assembly is affixed to a posterior surface of the vibratile piston. The magnet assembly comprises first and second permanent magnets located with respect to one another to bring like poles into facing opposition. The facing like poles are separated from one another by a ferromagnetic focus element.

Abstract: A hydrophone (10) for immersion in a liquid body defining a depth-dependent static pressure and a dynamic pressure. The hydrophone (10) includes a pressure-bearing element (11) for exposure to the liquid body; a motion sensor (13) spaced apart from the pressure bearing element (11); and a dilatant coupling material (14) disposed intermediate the pressure-bearing element (11) and the motion sensor (13) so as to mechanically transmit movements substantially corresponding to the dynamic pressure from the pressure-bearing element (11) to the motion sensor (13). The dilatant coupling material (14) does not transmit movements to the motion sensor (13) that substantially correspond to the depth-dependent static pressure.

Abstract: An acoustic vector sensor mounted in a housing is provided for measuring ultra low frequency acoustic wave particle velocities in a liquid, comprising a horn for amplifying the acoustic wave particle velocities, and a neutrally buoyant object supported in a liquid contained in the horn. The neutrally buoyant object, in reacting to the amplified acoustic wave particle velocities, produces displacements that are sensitively measured.

Abstract: A pressure-sensitive switch comprising an electrically-insulating base member having front and back surfaces with a through opening extending between the two at the center of the base member. Two electrodes are mounted on the base member's front surface and each have an electrically-conductive contact surface. A flexible diaphragm has its periphery secured in a fluid-tight manner to the back surface of the base member and is provided with a post connected to the central portion of the diaphragm. The post extends through the base member where an electrically-conductive washer is fixed to it where it extends beyond the front surface of the base member. A fluid-tight cap is secured to the front surface, covering an area above the washer and preventing fluid from entering the switch mechanism. The diaphragm, which is formed with plural corrugations, is exposed to the external pressure.

Abstract: An interferometric hydrophone operable for use in surrounding fluid, includes an outer mandrel having an interior open to the surrounding fluid. A sensing optical fiber is wound on the exterior of the outer mandrel. An inner mandrel is positioned in the interior of the outer mandrel. A chamber defined between the inner mandrel and outer mandrel is in communication with the surrounding fluid. The inner mandrel has a sealed gas filled interior. Compression and expansion of the inner mandrel results in compression and expansion of the outer mandrel.

Abstract: An interferometric hydrophone is disclosed that comprises a first mandrel defining an interior that is open to surrounding fluid. A sensing optical fiber is wound upon the first mandrel. A second mandrel is positioned in surrounding relationship with respect to the first mandrel. The first and second mandrels define a first chamber therebetween. A case encloses the first and second mandrels and first chamber. The cylindrical case and the second cylindrical mandrel define a second chamber therebetween, which is sealed and filled with gas or vacuum.

Abstract: A hydrophone which is automatically inhibited when the immersion depth exceeds a predetermined threshold by action, on the push element (7) of a switch (6), of a flexible wall that bends under the action of the outside pressure. The hydrophone comprises a tubular body (1) with two chambers (1a, 1b) separated by a partition (2). One of the chambers is closed by a flexible diaphragm (4). Switch (6) is fixed at the center of one of the chambers. Diaphragm (4) can push down on and actuate push element (7) by bending. The body can advantageously consist of two parts that can be screwed onto one another, which allows easier adjustment of the inhibition pressure. A pressure-sensitive reception unit (S) is arranged in the other chamber.

Abstract: Disclosed is an electrodynamic transducer designed to emit acoustic waves in a sea environment while being capable of withstanding external explosions. The lower pole piece of such a transducer is drilled with vertical holes enabling air to circulate inside the transducer in order to efficiently cool the coil that makes it work. Light metal masses that are good heat conductors, attached between the magnets which excite the pole pieces, furthermore drain the heat out of the transducer. The efficiency of such a transducer is increased by at least 4.

Abstract: Systems and methods of the invention can equalize the pressure between an interior cavity and an environment exterior to the interior cavity, while providing for acoustic isolation between the two environments so that acoustic energy propagating through one environment does not cause acoustic vibrations in the other environment. In one application, these pressure compensation systems are employed to equalize the pressure on either side of a moving coil projector, thereby reducing the deleterious effect that a pressure differential across the moving coil projector can have on the operation of the moving coil projector and reducing the likelihood that propagating acoustic energy can result in phase cancellation that reduces the acoustic performance of the moving coil projector.

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: Device (20) for measuring pressure waves in a liquid medium (E), comprising; one or more sensor elements (23) permeable to optical radiation; one or more support members (22) on which a sensor element (23) is arranged in each case and which is at least slightly flexible; a chamber (25) at least partly enclosed by a support member (22) and filled with the liquid medium; and a second compensation chamber (27) which is actively coupled to the first compensation chamber via an at least partially flexible wall (26), wherein the second compensation chamber is filled with gas; and detection means for detecting changes in the length of the sensor element.

Abstract: Disclosed is an electrodynamic transducer designed to emit acoustic waves in a sea environment. The dome of a transducer such as this is provided with a horn sliding in the body of the transducer with an adjutage whose clearance is extremely small. This reduces the effects of a shock wave coming from a possible external explosion and prevents the tearing of the tight-sealing membrane between the horn and the body. Radial ribs increase the stiffness of this mobile structure. A toroidal, elastic air chamber provides compensation for the effects of the hydrostatic pressure and of gravity on the mobile structure. The disclosure provides transducers that are resistant to external explosions.

Abstract: A sound amplification system includes an amplifier and a waterproof microphone. In an exemplary embodiment the microphone includes a transducer within a cavity covered by a resilient waterproof membrane. The system can monitor either the complete frequency range of the microphone or only one or more selected frequency ranges. The system can include one or more noise emitting lures that produce sound in a frequency range corresponding to the one or more selected frequency ranges. The invention also includes a method of waterproofing a miniature microphone.

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: In a flextensinal transducer a drive stack provided inside the oval shell has a strain compensator that has a cylinder and piston. The cylinder is provided in the oval shell, and the piston is stiffly attached to the end of the drive stack. Inside the cylinder, the piston can move along the major axis of the oval shell. When the flextensional transducer is sunk into the water, the oval shell is distorted to extend along the major axis. Then the cylinder and the piston moves relatively to each other to compensate for the distortion.

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 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 acoustic projector wherein a unitary acoustic resonator produces active sonar signals in more than one frequency band. The double-slotted resonator is coupled to a transducer which is capable of exciting the resonator in two, distinct, volumetric modes of vibration using two asymmetric, generally arcuate vibrating members. Transduction techniques can include variable reluctance or piezoceramic transduction. Internal cavity pressure release may be achieved by bladders, compliant tubes, and the like.

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 leak detecting microphone inserted directly into fluid within a pipe includes a housing having a first end being inserted within the pipe and a second opposed end extending outside the pipe. A diaphragm is mounted within the first housing end and an acoustic transducer is coupled to the diaphragm for converting acoustical signals to electrical signals. A plurality of apertures are provided in the housing first end, the apertures located both above and below the diaphragm, whereby to equalize fluid pressure on either side of the diaphragm. A leak locating system and method are provided for locating fluid leaks within a pipe. A first microphone is installed within fluid in the pipe at a first selected location and sound is detected at the first location. A second microphone is installed within fluid in the pipe at a second selected location and sound is detected at the second location.

Abstract: A device for mounting an ultrasonic transducer on user equipment for operation in a contaminating, ambient environment. A housing has a forwardly extending, profiled inner surface for promoting focusing along an axis of ultrasonic waves emitted by a transducer mounted against a shoulder of the casing. A chamber adjacent to a backside of the transducer is formed by a rearwardly extending portion of the casing and a cap forming an overlap portion therewith. A bladder disposed in the chamber has a port which vents into the overlap portion such that pressure equalization across the transducer is dynamically maintained. A calibrator offset by known displacement from the transducer provides a reflected wave portion to the transducer such that errors caused by temperature dependency of the velocity of propagation of the ultrasonic waves through the ambient environment can be substantially eliminated.

Abstract: There is described an optical acoustic sensor that is pressure-compensated for operation in high-pressure environments such as the deep sea and that may be employed in multi-sensor arrays. The sensor includes an acoustically responsive diaphragm that is illuminated by light conducted through an optical fiber and that reflects the light back into the fiber. Light waves reflected by the diaphragm and fiber end interfere, and the resulting interference is conducted by the optical fiber to a to a photodetector and associated signal processing electronics such as a phase generated carrier demodulator. Pressure compensation is provided to equalize the static pressure on both sides of the diaphragm. Additionally, an array of sensors is described that employs optical time division multiplexing.

Abstract: An acoustic array of special utility in deep operating antisubmarine torpedoes comprises a plurality of individual transducer elements supported by a back-plate member. An acoustic window made of an elastomeric or plastic material is mounted against the front faces of the transducer elements and forms part of the water-proof housing of the torpedo. The backplate provides abuttive support to the transducer elements against crush pressure exerted by ambient water against the acoustic window. Inserts, made of an acoustic decoupling material which exhibits high crush strength characteristics, are interposed between each transducer element and the backplate. The backplate is made of body sections having interposed therebetween very thin layers of a compliant material, with the layers bondingly confined between the body sections. The compliant material is chosen to be of a type which damps acoustic vibrations which may be present in the backplate by the mechanism of "coulomb friction damping".

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 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 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: A method and apparatus (10) for sensing sound in a fluid medium. The apparatus (10) includes an element (12) for generating polarized light having a predetermined plane of polarization. In addition, the apparatus (10) further includes an element (14) for rotating the plane of polarized light in response to sound waves propagating in the fluid medium, as well as an element (32) for detecting the polarized light. Finally, the apparatus (10) includes an element (34) for generating a signal from the output of the detecting element (32) which is indicative of the amplitude and frequency of the sound waves.

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: A sonar projector having a pair of opposed oscillating pistons driven by an electromagnetic assembly is rendered capable of operating at reduced resonant frequency by providing liquid mass loading for the pistons. The mass loading is achieved by utilizing a structure which constricts a body of liquid on one side of the piston. The constricted liquid may be sea water or liquid sealed within the body of the unit. In accordance with a further aspect of the invention, a seal assembly is provided for the moving pistons which not only provides a sealing function but which also acts to radially center the pistons and to provide an axially directed restoring force thereto during piston oscillation. The electromagnetic assembly, in accordance with still a further aspect of the invention, is formed with a permanent magnet structure arranged in a cylindrical configuration with the opposed pistons on opposite axial ends thereof to reduce magnetic leakage losses.

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

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

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

Abstract: The apparatus of the present invention detects the resonant frequency of a vibratory member in contact with a fluid. The detection of the resonant frequency enables the device to be used to detect the density of a fluid which it is in contact with and thereby calculate the flow rate of the fluid. The vibratory member is mounted in a housing in such a way that the chambers on either side of the vibratory member have equal volumes. The fluid enters the device through a conduit and then divides into two equal tubes on either side of an extension of a vibratory member extending down these tubes. The apparatus for measuring the resonant frequency of the vibratory member is mounted on the vibratory member and is comprised of a piezoelectric element coupled to a driver circuit in a feedback loop.

Abstract: This invention relates to a device for maintaining the gas contained in a submerged enclosure in pressure equilibrium with the outside, comprising a plurality of deformable bags which are immersed at the same time as said enclosure which are filled with gas compressed to different pressures and which communicate with said enclosure via a manifold on which they are connected by automatic three-way valves.

Abstract: The present invention provides a pressure compensated communication system having at least one audio transducer, the pressure compensated communication system comprising a fluid tight housing for the or each audio transducer, the or each housing having a corresponding one of the or each of the audio transducers located therein and having an orifice coupled to a pressure compensation means, the pressure compensation means connected to the or each orifice and to a continuous supply of gas at a pressure equal to or slightly greater than the pressure of liquid surrounding the housing.

Abstract: A tubular piezo-electric sensor has at least one sensitive element disposed against an outer surface of a tubular support. A substance whose acoustic impedance is very different from that of the material forming the tubular support is disposed therein and a remaining volume of the tubular support is filled with liquid. Glass fiber cords or open cell foams, for example, are used as the substance, and the liquid may, for example, be that which fills a seismic streamer and, in this case, the tubular support is left open. The tubular support may also be closed at both ends by sealed caps and included in a protective sheath. The dimensions of the tubular support and the material from which it is made are chosen so as to optimize the sensitivity of the piezo-electric sensor.

Abstract: This invention relates to an underwater transient sound generator capable of operating at substantial depths. The pulse produced by the generator is used to determine subbottom terrain in underwater surveying. Essentially, the invention consists of an electromagnetic coil, which is embedded in an annular support body with a central hole. A piston is located next to the coil, but is separated therefrom by a dielectric sheet. A rubber seal and spring are used to locate the piston in position. A body portion extends back from the support body with two open ends. The rear end is covered with a water tight flexible diaphragm and the front end connects with the central hole of the support body, defining a watertight pressure transfer space, containing a pressure transfer medium. The coil is capable of being energized to rapidly displace the piston to a forward position. Two embodiments are shown in which the pressure transfer medium is either a gas or a fluid.

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 deep-water low-frequency transducer employs a collapsible air chamber to equalize the internal transducer air pressure with the external hydrostatic pressure at the submerged operating depth. A capsule containing a highly pressurized gas is mounted inside the collapsible air chamber and an automatic valve mechanism releases the gas to inflate the collapsed air chamber at a predetermined depth, beyond which any further reduction in the air volume would impair the operation of the transducer. With the collapsed air chamber restored to its original full volume, the transducer will operate satisfactorily at increased water depths.

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.