Abstract: The present invention generally provides an apparatus and method for improving the process of purging a liquid delivery system used in integrated circuit manufacturing. The liquid delivery system comprises ultrasonic transducers mounted to various components of a liquid delivery system. The transducers may be mounted on housings, isolation valves, fuel injectors, pump assemblies, fluid lines, and/or liquid flow meters. The ultrasonic transducers launch ultrasonic energy that enhance the removal of processing liquids and particulate material from components of the system. The present invention provides for a purge process where a purge fluid, preferably a liquid solvent, is flowed into the liquid delivery system and ultrasonic energy is launched into the purge fluid to enhance dissolution of residual processing liquids and particulate matter in the liquid delivery system, including from cracks and crevices in valves and other complex mechanical devices before being pumped from the liquid delivery system.

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: The present invention provides a microfabricated acoustic transducer with suppressed substrate modes. The modes are suppressed by either thinning the substrate such that a longitudinal ringing mode occurs outside of the frequency band of interest or by applying a judiciously designed damping material on the backside of the transducer substrate.

Abstract: An ultrasonic sensor has a sensor body, a diaphragm, and a vibrator for generating ultrasonic and attached to the diaphragm. The diaphragm has a thinnest portion. The thinnest portion has a predetermined thickness by which reverberation of the diaphragm is restrained. The reflected ultrasonic can be detected correctly by this construction of the sensor.

Abstract: An electro-acoustic transducer is manufactured by forming a transducer assembly at least one piezoelectric element, electrodes contacting the element, and acoustic loading blocks, and applying successive superposed mouldings of material of differing acoustic properties around said transducer assembly to form the transducer, while maintaining electrical coupling between the transducer assembly and the exterior of the transducer, the mouldings providing at least one acoustic matching layer covering a radiating surface of the transducer assembly, a casing surrounding the remainder of the transducer assembly, at least one layer of acoustic isolating material between the casing and the transducer assembly. The successive layers may either be moulded in situ, or moulded separately and then assembled.

Abstract: A well tool in accordance with the invention comprises an attenuation device which attenuates tube waves associated with an elastic wave emission and/or reception set (1, 12). The attenuation device comprises a bubble generator (2) which releases into the well a gas not readily soluble in the well fluid, slightly overpressured in relation to the hydrostatic pressure, in the form of calibrated bubbles which greatly attenuate the parasitic tube waves. The attenuation device is placed above or below the elastic wave emission and/or reception set having a plurality of pickups whose signals are acquired by a local electronic module (14) and/or a source of elastic waves such as a vibrator. A bubble trap (17) is preferably associated with the bubble generator (2) in order to limit the volume of gas to be generated in situ. The invention is applicable to VSP type seismic prospecting and acoustic logging.

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 slotted cylinder transducer is provided having a cylindrical metal or cosite material shell. A cylindrical piezoelectric driver is bonded to the inside of the shell with an opening corresponding to the slot. The shell thickness is tapered radially about the longitudinal axis such that the thickness is a maximum 180.degree. away from the slot and decreases progressively to a minimum adjacent each side of the slot. The piezoelectric driver is reverse tapered from the shell taper in that the thickness of the driver is a minimum 180.degree. away from the slot and increases progressively to a maximum adjacent each side of the slot. This taper places a larger volume of the driver material in the slot region of the shell where the maximum radial displacements occur, thus providing higher acoustic energy levels. When used as a hydrophone to detect acoustic signals in the surrounding medium, the larger volume of material at the point of maximum displacement provides increased signal detection capability.

Abstract: A nose cone for attachment to an underwater vehicle for shielding a sonar ray in a nose portion of the vehicle from acoustic pressures in a water environment, the nose cone comprising a tubular body for surrounding side wall portions of the vehicle nose portion, a cap fixed to one end of the nose cone body for overlying a forward-most portion of the vehicle nose portion, and bleed tubes extending through the body and/or cap for permitting air to escape from between the vehicle nose portion and the nose cone when the nose cone is placed on the vehicle nose portion. There is further contemplated a method for acoustically shielding sonar arrays in nose portions of underwater vehicles, which includes utilization of the aforementioned nose cone.

Abstract: In a preferred embodiment, a flexural plate sound transducer (150), including: a housing (152) having an open central volume (172); a flexural plate (154) attached around an inner surface of the housing (152) and extending across the central volume (172); at least one piezoelectric element (162, 164) attached to a surface of the flexural plate (154); and a mechanical hinge (194) formed in the flexural plate (154) and extending around the flexural plate (154) near an outer periphery thereof, the mechanical hinge (194) being formed such as to cause the flexural plate (154) to move in a substantially piston-like manner when the piezoelectric element (162, 164) is energized.

Abstract: An ultrasonic range finder which can effectively suppress the influence of direct transmission waves is provided. An ultrasonic range finder according to the present invention comprises a transmitting ultrasonic sensor, a receiving ultrasonic sensor, and a case which holds both ultrasonic sensors mounted and separated on the same surface, wherein a foam member fabricated to contain air bubbles is provided between the ultrasonic sensors within the case and the foam member is exposed to the surface of the case. Each of the sections of the transmitting and receiving ultrasonic sensors (which are held within the case) are covered with a second foam member and the matching layer sections of the transmitting and receiving ultrasonic sensors project beyond the surface of the case.

Abstract: A state switched acoustic has a stiffness element having a zero potential energy state and a plurality of controllable stiffness states. A mass is coupled to the stiffness element so that the stiffness element and the mass are capable of resonating at a resonant frequency. A system changes the stiffness state of the stiffness element from a first stiffness state to a second stiffness state while the mass is in motion and stiffness element is in a zero potential energy state so as to change the resonant frequency of the transducer. In a method of changing resonant frequency of a mechanical system, a parameter of the system is dynamically changed while the system is in an energy state that will allow changing the resonance parameter without disrupting the resonance of the system.

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: 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: Active and adaptive vibration damping devices are provided. The damping devices include heterostructures having a layer of ferroelastic or SME material coupled with a first and second layer of ferroelectric material having a layer of dielectric material therebetween. Methods of making the active and adaptive vibration damping devices are also provided.

Abstract: A sonar transducer displaying improved reliability and operating characteristics by employing multiple ceramic stacks, novel support structure and an improved gaseous environment.

Abstract: This invention relates to an ultrasonic generator apparatus for generating and transmitting enhanced ultrasonic wave energy of a predetermined frequency to a liquid confined in a container which contains a resonance enhancing disc. Such electroacoustic transducer apparatus or generators are utilized in ultrasonic cleaning equipment. The apparatus are mounted to the side or the underside of the liquid container or mounted in a sealed enclosure which is immersed in a liquid in a container made of metal, plastic or glass. Generators are used in single or plurality of to energize the liquid with sonic energy which in turn transformed into cavitations. In the present invention, the insertion of a resonance enhancing disc between the base of the generator and the piezo electric material provides an increase in intensity of the resonant frequency signals, diminishing periodical shift in frequency and stabilizing piezo electric material temperature.

Abstract: A piston transducer having a central longitudinal axis and at least one piston member and an active transducer section displaced from one another along the longitudinal axis. Movement of the active transducer section is generally in a plane perpendicular to the longitudinal axis and a series of lever arms couple the movement of the active transducer section into a corresponding axial movement of the piston member and which axial movement is with a uniform velocity across the radiating surface thereof. For two-sided radiation, another piston member and series of levers may be connected to the active transducer section.

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: An ultrasonic transducer assembly for generating and receiving ultrasonic vibrating forces comprises an ultrasonic transducer and a unitary housing for mounting to a marine vessel. The housing has a cavity formed therein for disposing the ultrasonic transducer. An acoustic window portion transmissive to the sonic vibrating forces is formed in the bottom of the housing. The ultrasonic transducer includes a transducer element having a cork layer on its sides and inner foam layer on its top surface. A potting material such as urethane encapsulates the ultrasonic transducer in the cavity. A portion of the potting material forms a potting layer between the bottom surface of the transducer element and the acoustic window portion of the housing.

Abstract: The invention relates to multifrequency acoustic transducers exhibiting a wide band around each resonant frequency. It consists in inserting between a .lambda./2 active emitter plate (201) and the soft reflector (203) which supports it a rear plate (202) resonating in .lambda./4 mode and in placing on this active plate two marcher plates (204, 205) whose impedances are designed so as to best match the two frequencies obtained by inserting this rear plate. Thicknesses of these marcher plates are optimized with the aid of a model of for example Mason type starting from a value close to .lambda./4 for the frequency to be matched. It makes is possible to construct sonar transducers which operate equally well in detection mode and in classification mode.

Abstract: A surface element for a device for generating sounds by influencing opposite extremities of a surface element to oscillate from and towards each other and thereby the surface element to oscillate transversely thereto and generate sounds has at least a portion formed in the thickness direction thereof by at least two first layers (12) and an intermediate layer (13) having a lower average density than the density of the two first layers.

Abstract: The invention is directed to the class of submersible electro-acoustic transducers such as double "Tonpilz" transducers, wherein it is desirable to reduce the resonant frequency of the transducers while maintaining a given output power emitted by the transducers. The transducer according to the invention includes at least one horn solid with the end of a motor pillar, a hollow rigid box surrounding the horn and delimiting with the horn a cavity. The cavity communicates via a port with an external fluid, and has determined dimensions and external volume. The transducer further includes a passive radiator made of a material denser than the external fluid. The radiator obturates the port and hangs at a periphery of the port by an elastic material.

Abstract: This ultrasonic transducer has a high chemical resistance and a small diameter and can be used over a very wide temperature range. It has a single-piece, can-shaped housing (1) sealed off by a diaphragm (12), a sensor element (2), arranged in the housing (1), for transmitting and receiving ultrasound, a matching layer (3) arranged between the diaphragm (12) and the sensor element (2), a stress equalizing layer (5) which completely encloses the sensor element (2) apart from a front area adjoining the matching layer (3) and is made of a thermosetting plastic, especially of an epoxy resin, a clamping ring (4) coaxially enclosing the matching layer (3), and a damping layer (6) that fills a cavity that remains in the housing (1) and is bounded by the clamping ring (4), the stress equalizing layer (5) and the housing (1).

Abstract: A two phase composite acoustic backing for an ultrasonic transducer array is formed of a first composite material which is electrically conductive and relatively attenuative to acoustic energy and forms a plurality of isolated conductive paths between individual elements of the array and the back side of said backing. The isolated conductive paths are surrounded by an acoustic kerf filler material which is non-conductive and is either attenuative to acoustic energy, exhibits a low acoustic impedance, or both. The resulting two phase composite acoustic backing thus attenuates ultrasonic energy which enters the backing from the transducer elements, both in the conductive paths and in the surrounding kerf filler material, while affording points of electrical attachment to cable wires for the array which are removed from the piezoelectric material.

Abstract: An acoustic transducer includes a support structure which holds an acoustic pulse generator having both a front application face and a rear face. An acoustic absorber is attached to the rear face of the pulse generator. An acoustic isolator is positioned between the acoustic absorber and a support structure/heat sink. A preferred embodiment of the acoustic isolator includes at least a first material layer exhibiting a first acoustic impedance value, and a second material layer exhibiting a second acoustic impedance value. The second acoustic impedance value is substantially different from the first acoustic impedance value. A boundary between the first material layer and the second material layer causes multiple acoustic reflections of an acoustic pulse emanating from the rear face of the pulse generator. The first material layer and second material layer both exhibit substantial heat transfer capabilities.

Abstract: A multilayer composite transducer is disclosed. The multilayer composite transducer comprises a plurality of layers wherein a piezoelectric material is dispersed periodically within a polymer matrix. The piezoelectric material is typically formed into columns or slabs, and these columns and slabs need to be aligned from one layer to the next. As this alignment can be difficult to perform, the present invention teaches a first method for fabricating the multilayer composite transducer which allows the alignment to be easily accomplished and a second and third method which reduce or eliminate the need for the alignment.

Abstract: An absorbent passive acoustic antenna, designed to be attached to the hull of a ship, is made in the form of a stack of layers of polyurethane having different types of composition to obtain absorbent and/or reflective characteristics so as to minimize the parasitic signals received by the hydrophones and achieve the maximum absorption of the signals coming from the active sonars external to the vessel on which these antennas are placed.

Abstract: A high frequency transducer capable of transmitting and receiving having an operational range from 100 kHz to 2 MHz, a free field voltage sensitivity (FFVS) greater than -218 dB re 1 V/.mu.Pa (300 kHz), and a maximum hydrostatic pressure rating of 20.68 Mpa (3000 psi). The sensor element is made of lead titanate with a radial mode of 150 kHz being suppressed by the use of a rubber grommet surrounding the lead titanate element. The sensor element is retained within a sensor housing by a plurality of annealed iron wires attached to an annealed iron ring, both of the faces of the sensor housing are then covered with an acoustically transparent window of natural gum rubber. The sensor housing is attached to a non-metallic preamplifier housing made of a rigid polyurethane containing a preamplifier circuit, a transmit protection circuit, and a plurality of relays for switching the preamplifier circuit during the transmit and receive modes.

Abstract: An acoustic antenna includes at least one surface sensor formed by a stack of conducting materials and dielectric layers of piezo-electric material enclosed in a sheathing of flexible material. The assembly forms a flat panel 2 mounted against the hull 5 of a navel vessel and takes the shape of the hull. The mounting of the panel on the hull is achieved by two streamlined edging sections 3, 4 while leaving an intermediate water layer 6 remaining between the panel 2 and the hull 5. The sheathing includes an envelope of flexible material filled with a visco-elastic lining material and the piezo-electric material of the dielectric layers of the sensor is preferably a polyvinylidene fluoride film.

Abstract: 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 rib-stiffened sound wave projector plate is disclosed which generates low requency sound waves in a fluid medium when energized and flexed. A flexible sound wave projector plate includes at least first and second parallel, major planar surfaces. The first major planar surface includes at least one set of sound wave projector plate ribs, disposed perpendicular to the first major planar surface. Each set of sound wave projector plate ribs includes at least first and second sound wave projector plate rib set members. Each member of the rib sets are offset or spaced laterally from one another by a first predetermined distance, while the first rib member of each rib set is spaced apart a second predetermined distance which is greater than the first distance between the rib set members. Further, each rib set member has a predetermined height and width which may vary from other rib set members in each rib set.

Abstract: An apparatus for sensing acoustic signals in a liquid wherein an omnidirectional hydrophone exhibits a hemispheric response pattern. A hydrophone, including a transducer element and a transmitting cable, is mounted such that the transducer element is adjacent the forward face of an acoustic baffle including a layer of sound-absorbing material. The rear face of the acoustic baffle is positioned adjacent an acoustic shield including a layer of sound-reflecting material. The transmitting cable is positioned in an aperture in the acoustic baffle and the acoustic shield, and passes beyond the rear face of the acoustic shield. A flow fairing is positioned adjacent the forward face of the acoustic baffle and encloses at least the forward portion of the transducer element.

Abstract: A decoupling ring provided on the front annular face of the nose shell of a craft, surrounding the sonar array. This ring decouples the vibration in the nose shell from the fluid path. The decoupling ring is constructed of one or more mass elements on one or more compliance elements. The individual compliance elements are preferably vibrationally speaking springs and the mass elements are preferably metal segments which form a mass-spring system. The dimensions and characteristics of the mass and compliance rings are chosen to have a fundamental resonant frequency well below the sonar frequency range of interest, thus acting as a low pass filter. When the vibrational energy has a frequency above the resonant frequency of the mass spring system, the vibrational energy is attenuated effectively. The low frequency resonance of the decoupling ring is obtained by using a large mass and a large compliance in the mass and compliance elements, respectively.

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

Abstract: The invention relates to processes and electro-acoustic transducers for transmitting low-frequency acoustic waves in a liquid. An electro-acoustic transducer according to the invention is a transducer of the double-tonpilz type, comprising two electro-acoustic drivers (1a, 1b) in line on both sides with a central counter-mass (2) and between two horns (3a, 3b). This mechanical assembly is located in a rigid box (4) which is fitted with side holes (5) and which delimits a cavity (7) housing elastic tubes (6) closed at their both ends and filled with gas so that the Helmholtz resonant frequency of the cavity (7) is close and preferably lower than the fundamental frequency of the axial vibrations of the vibrating assembly. An application of the invention is the construction of low-frequency transmitting transducers of the double-tonpilz type with a wide pass-band.

Abstract: An acoustic transducer having impedance matched layers that can be deployed in environments having wide temperature variations. An anisotropic layer provides a low coefficient of thermal expansion orthogonally to the direction of sound wave propagation. The anisotropic layer may be a solid matrix embedded with fibers, such as glass, arranged in a common orientation.

Abstract: A piezoelectric acoustic transducer for coupling acoustic energy to a gaseous atmosphere in a pulse-echo ranging system has a tubular housing closed at one end by a thin integral wall to which a radiating plate of a transducer assembly is coupled to radiate acoustic energy by means of a layer of acoustically transmissive matching material. The transducer assembly except for its radiating surfaces is wrapped in an acoustic decoupling material such as cork, and the side wall of the tubular housing, which has a mounting ring behind the transducer assembly, is also internally lined with such material, space around and behind the transducer assembly within the housing being filled with a slightly elastomeric potting compound. This arrangement decouples the mounting ring from the transducer assembly, thus stabilizing the ringing characteristics of the transducer.

Abstract: An acoustic sensor and projector module for sonar applications includes a first acoustic transducer element operating as a projector to generate an acoustic beam, and a second acoustic transducer element acting as a hydrophone to sense pressure wave returns. When the second acoustic transducer element operates in a sensing mode, the first acoustic transducer element serves in conjunction with a baffle structure to baffle acoustic signals presented to the hydrophone. Similarly, when the first transducer element operates in a projecting mode to generate an acoustic beam, the second transducer element acts in combination with a baffle structure to baffle acoustic signals emitted by the projector.

Abstract: A resonance oscillator comprises an active, e.g. disk-shaped, oscillator part (2) which is brought into contact, forming a couple oscillator, with a passive, comparatively longer oscillator part. This oscillator part, which basically determines the resonant frequency, consists of a variable-length solid column or liquid column (11) the length of which can be varied continuously in the direction of the sound vector in order to change the resonant frequency. The active oscillator part (2) is mounted on the base of an elongated resonance container (6) which contains the liquid that forms the liquid column (11). The length of the liquid column is varied by sliding a piston (5). The resonance container (6) is bounded by a corrosion-resistant, high-strength covering disk (7) of minimal thickness and is connected to an equalizing container (9) which receives the liquid displaced by the piston from the resonance container and returns the liquid to the resonance container.

Abstract: An element responsive to acoustic particle acceleration for sensing acoustic signals in a region of low acoustic pressure is disclosed. The element may be isolated from acoustic noise when positioned adjacent an acoustic noise generating high acoustic impedance structure by a baffle which provides isolation from radiated and evanescent acoustic signals and structure vibration.

Abstract: An acoustic transducer assembly is provided having a one or two dimensional array of transducer elements, an electrical circuit element such as a circuit element and a backing for interconnecting transducer elements to corresponding contacts or traces of the circuit element. The backing is a block of acoustic attenuating material having a conductor extending therethrough between each transducer element and the corresponding circuit contact. The block has acoustic properties, including acoustic impedance and acoustic velocity, to achieve a desired degree of acoustic match with the transducer elements and/or to permit coupling of acoustic energy from the conductors into the block. The block may be of a single material or may have different volumes of two or more materials having different acoustic properties to achieve desired results. Multiple thin conductors or conducting fibers or foils may be utilized for each transducer element to reduce or eliminate acoustic coupling into the conductors.

Abstract: A side-looking sonar transducer which has sound absorbing material extending forwardly of the active surface of the transducer elements to diminish the acoustic response over a predetermined zone for reducing the effect of erroneous reflection signals. The surface of the sound absorbing material has a series of sharp peaks and valleys.

Abstract: A broadband electroacoustic transducer is disclosed which provides an improved response over a relatively broad range of frequencies. The transducer includes a plurality of tines extending between the outer circumferential surfaces of a pair of piezoelectric cylinders. The cylinders are disposed about a common axis and are separated by a gap. The tines extend longitudinally across the gap from one cylinder to the other. Each tine is separated from the adjacent tines by a space which is sized to prevent contact between the tines when the cylinders radially oscillate. A pre-stress wrap is disposed over the tines on both sides of the gap to provide a static, inwardly radial force on the cylinders.

Abstract: A multiport underwater sound transducer including a hollow resilient housing enclosing a volume with at least two ported resonant chambers and a transduction driver disposed within the volume with opposite sides of the driver driving the two chambers. The two ports are set to resonate at slightly different frequencies and the tranducer proudces an additive output at frequencies between the two slightly different frequencies due to phase reversals of oppositely phased sound waves.

Abstract: 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.

Abstract: A seismic source for downhole use is disclosed which is formed by an outer tubular member having weighted ends which carries within a coaxially mounted tubularly shaped piezoelectric element. The piezoelectric element is cyclically driven to produce a standing wave having a frequency in the range of 0.25 to 5 kHz and a narrow bandwidth in the range of 5-50 Hz.

Abstract: A sonar array which is operable at a broad range of frequencies, has a high free-field voltage sensitivity and is operable at high hydrostatic pressures. The array includes sensor elements made of a piezoelectric material, a backing plate which supports the sensor elements, a dielectric-elastic insulator positioned between the sensor elements and the backing plate, and backing blocks corresponding, respectively, to the sensor elements, each backing block positioned between a corresponding sensor element and the insulator. The sensor elements are arranged in staves, the staves forming four separate quadrants, the sensor elements in each stave being arranged in parallel and series combinations, so that the sonar array is operable between a frequency range of 10 kHz to above 100 kHz, each stave has a free-field voltage sensitivity of -186 dB re 1V/.mu.