Abstract: A low frequency sonar transducer comprising a head (1) having first and second stacks of piezo ceramic elements (2,3) in two spaced apart planes between common nodal end supports (7,8), the stacks being oppositely polarized to act in push-pull action with one stack expanding and the other contracting to cause the head (1) to bow. The transducer is prestressed with fibres (6) to prevent fracture.

Abstract: A towed piezoelectric cable having a plurality of receiver element units which are arranged on a nonshrinking flexible core with leaving a buffer zone therebetween, each of said receiver element units having two piezoelectric elements which are polarized in a predetermined direction, and are provided with inner electrodes connected to each other and outer electrodes between which an output signal is produced, respectively, the assembly of said receiver element units and said flexible core being contained in a flexible tube which is filled with an insulating oil.

Abstract: The present invention is directed to an ultrasonic device comprising a plurality of transducer elements arranged in rows and columns and acoustic insulation material maintained between each two adjacent rows of transducer elements. The ultrasonic device comprises (i) a plurality of rows of the transducer elements, each row being disposed on an imaginary circle, (ii) a plurality of circular plates each supporting one of said rows and (iii) spacers for spacing adjacent plates of the plurality of plates at a predetermined space interval, thereby forming a cylindrical array.

Abstract: An acoustic element assembly used in underwater receivers and projectors comprises two piezoelectric elements bonded to opposite sides of a hybrid circuit substrate (16). The hybrid circuit substrate (16) includes radial slots (32, 34, and 36) which have been cut therethrough. The radial slots (32, 34, and 36) permit a center section (31) to move bidirectionally. Integral micro-electronic circuitry which makes up the receiver or projector is fabricated in the center section (31) on both sides of an alumina ceramic disk (30) using thick and thin film technologies. Piezoelectric cylinders (12 and 14) or piezoelectric hemispheres (22 and 24) are bonded to opposite sides of disk (30) with both conductive and non-conductive bonding materials. The microelectronic circuitry is electrically connected to said cylinders or hemispheres (12, 14, 22, and 24) by conductive lines (44). The acoustic element assembly may be formed by automated techniques and does not require any internal wiring.

Abstract: A piezoelectric transducer assembly for producing sonar signals for transmission underwater and for detecting reflected sonar signals. The assembly includes a two-dimensional generally planar array of piezoelectric elements disposed in an elastomer casing. The elements are coupled by way of conductors to electronic circuitry which produces electrical signals for stressing the piezoelectric elements and which processes electrical signals produced by the piezoelectric element in response to reflected sonar signals. The piezoelectric elements are closely packed and are selected to have low cross-coupling characteristics. At least some of the elements are oriented so that their axes of polarization are generally perpendicular to the plane of the array.

Abstract: An acoustic transducer for providing large displacements particularly at low acoustic frequencies is formed from a minimum of three curved shells which are attached to each other at their ends. The shells are driven by a ring or corresponding number of attached piezoelectric or magnetostrictive type rod or bar drivers. The curved shells are attached to the ends of the driver and vibrate with a magnified motion as the rods execute extensional motion. As the polygon expands the curved shells deform and produce additional motion in the same radial direction resulting in a large total displacement and corresponding large acoustic output.

Abstract: A distributed array hydrophone comprising an array of hydrophones each comprising a ceramic doublet assembly of hollow radially oppositely polarized members end held in a bobbin by decoupling means, the bobbins being linearly interconnected by semiflexible spacing members, the array being encapsulated in a vibration transmitting potting medium in a tube formed of a pressure-wave transmitting medium.

Abstract: Piezoelectric transducer for the production of, for example, hydrophones, with the transducer including a plurality of sensitive coaxial elements interconnected so as to compensate for the effects of accelerations and deflections.A transducer includes at least one pair of sensitive elements composed of sections of radially polarized coaxial piezoelectric cables having an opposing orientation, with an external armouring of one being connected with an internal armouring of the other, and vice versa. By increasing the number of parts of sensitive elements and selecting the relative disposition, it is possible to improve the immunity of the transducer to noise due to accelerations and deflections, regardless of the direction or the need to license a direction where the transducer is sensitive to such noise. A predetermined number of pairs of sensitive elements can be combined around a central column for accommodating connectors or cables.To be applied, for example, to the production of hydrophones.

Abstract: An acoustic transducer array includes a number of transparent continuous aperture transducer elements which are aimed at various angular sectors in a field of view and are embedded in an acoustically transparent material such as casting resin. Each transducer provides a beamformed output, and the transparency of the elements ensures that each element observes an acoustic field that is unperturbed by the other elements. A high resolution and a wide field of view are obtained by overlapping the transducer elements so that each element captures an increased area of acoustic signal. Preferably, the transducer elements are cut from thin, flexible metalized sheets of voided piezeoelectric polymer such as polyvinylidene fluoride or polyvinyl fluoride co-polymer. The polymer transducers are broad band in nature, and permit multiple frequency, multiple beam sonar configurations.

Abstract: A hydrophone array wherein each individual hydrophone of the array is comprised of, e.g. polyvinylidine fluoride (PVF.sub.2), tiles bonded to a substrate member opposite one another on opposite surfaces of the substrate. The substrate is a relatively stiff, metallic member having a Young's modulus of at least an order of magnitude greater than the PVF.sub.2 tiles which are oriented such that their stretch directions on either side of the substrate are parallel to one another. The directions of polarization of the tiles are either the same or opposite and electrical connections are made such that for a predetermined relative orientation of the directions of polarization, any output signal which may be caused by flexing or acceleration of the substrate is substantially reduced or eliminated.

Abstract: A transducer is comprised of a piezoelectric ceramic cylindrical vibrator vibrating radially, and a sheet provided on an outer peripheral surface of the cylindrical vibrator and including a fiber reinforced composite material with fibers oriented only in the direction of central axis of the cylindrical vibrator. Non-piezoelectric cylinder consisting of Al alloy or Mg alloy may be useable instead of the sheet. Another type of transducer includes a cylindrical piezo-transducer vibrating radially, a cylindrical sound radiator with the central axis coincident with the cylindrical piezo-transducer, and a bending coupler provided at a predetermined interval on end surfaces of the two cylinders and coupling the cylindrical piezo-transducer and the cylindrical sound radiator.

Abstract: For increasing the bandwidth of an electroacoustic omnidirectional transducer a piezoceramic tube is provided at its outer circumference with segment-shaped additional mass members having a larger outer surface area than the piezoceramic tube.

Abstract: A piezoelectric polymer (PVDF) hydrophone array consists of multiple layers disposed symmetrically about a stiffener layer. The stiffener layer prevents flexural modes in the operating frequency band and provides a mounting structure for acceleration noise cancellation. The piezoelectric polymer layers are attached to the stiffener layer either directly or through intervening layers which provide mechanical vibration isolation of the polymer and stiffener layers.

Abstract: A cylindrical array employs rectangular planar array segments which extend in the axial direction when assembled on a cylindrical conducting plate having flat longitudinal portions to which the planar array segments are attached. Each planar array segment comprises two columns of planar transducer elements with each column extending in the axial direction of the cylinder. The acoustic center of each transducer lies on the circumference of a right circular cylinder. The acoustical requirements of a cylindrical array are satisfied to allow multiple beams to be formed with a minimum of complexity and with the same versatility as in the curved array segment cylindrical array embodiment.

Abstract: An underwater sonar transducer includes a centrally located beam with a plurality of stacks of piezoelectric transducer elements extending from each side, with a rigid end beam at the opposite end of each stack. A plurality of bolts extending from one end beam to the other on opposite sides of the stacks are tightened to apply a desired amount of prestress on the ceramic stacks. Arcuate radiating elements are welded to opposite sides of each end beam, end cap members are fastened to the centrally located beam at each end of the transducer and a jacket of elastomeric material is bonded to the edges of the end cap members to prevent ingress of fluid into the piezoelectric elements. Energizing of the piezoelectric elements causes expansion and contraction of the stacks, pushing the end beams in and out and causing bowing of the radiating elements to project sonar energy.

Abstract: An electro-acoustic transducer according to the invention is of the Tonpilz type comprising a stack of piezo-electric plates placed between a horn and a countermass, and electrodes inserted between the plates. Some of the electrodes are connected to a common excitation or output conductor through phase-shifting circuits which allow the electric voltage of a proportion of these electrodes to be dephased. A logic unit allows the phase-shifting of the electrodes to be distributed within the stack according to several different groupings in dependence upon frequency. One application of the invention is to the construction of long-range power sonars.

Abstract: An acoustic transducer for providing large displacements particularly at low acoustic frequencies is formed from a minimum of three curved shells which are attached to each other at their ends. The shells are driven by a ring or corresponding number of attached piezoelectric or magnetostrictive type rod or bar drivers which take the form of a regular polygon. The curved shells are attached to the ends of the driver and vibrate with magnified motion as the rods execute extensional motion. As the polygon expands the curved shells deform and produce additional motional in the same radial direction resulting in a large total displacement and corresponding large acoustic output.

Abstract: A cylindrical shell enclosure has mounted interiorly thereof in cantilever manner four upstanding laminated planar flexible resilient electroacoustic transducer reeds. A separate inertia weight is affixed to the top edge of each reed. An acoustic wave impinging on the side wall of the submerged enclosure will cause relative movement between the enclosure and a weight if the wave direction has a component transverse to the plane of the reed on which the weight is mounted. The reeds are mounted in quadrature so that wave direction detection is provided by comparing the electrical outputs of the reeds. Viscoelastic damping pads may be affixed between the side ends of each of the weights and respective upstanding rigid arms secured to an interior surface of the enclosure.

Abstract: Omnidirectional sonic transducers suitable for underwater operation as either hydrophones (listening devices) or projectors (sonic sources) are disclosed. The transducing device has a hollow resonant cavity with at least one flexural disk mounted therein in acoustic communication with both the interior and exterior of the cavity. The cavity also has at least one aperture providing acoustic coupling between the cavity interior and exterior, and a pliant lining covering substantially the entire cavity inner surface except for flexural disk surfaces and the aperture to detune the natural cavity resonance by reducing the rigidity of the cavity inner surface, thereby improving the overall frequency response characteristics of the transducing device.

Abstract: Underwater piezoelectric arrangement in which it comprises two piezoelectric layers made of piezoelectric ceramic-polymer composites, one of the layers has larger hydrophone constant than that of the other layer, and by noise cancelling based on the specific construction of the piezoelectric layers only charges or voltages generated by acoustic waves which act on each layer can be selectively detected. The piezoelectric arrangement may be utilized to provide a piezoelectric cable for use in a submarine earthquake searching or fish finding hydrophone, or an acoustic measuring element under water.

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

Abstract: A composite layered assembly of piezoelectric polymer layers and printed wiring layers are configured so that plated-through holes make electrical connection from the outputs of a plurality of polymer hydrophones formed on one or more polymer layers to a plurality of output conductors on a single plane after each hydrophone output is amplified in its associated amplifier.

Abstract: A long, continuous, constant diameter, neutrally buoyant oil filled line array hose without couplings comprising a plastic inner hose having a layer of conducting and/or optical fibers wrapped helically around and bonded to the outer periphery along the neutral axis thereof. A strength member layer is encased within and bonded to an outer plastic sleeve which covers the conducting layer. Sensors are placed within the inner hose cavity through incisions formed at predetermined locations, attached to the conducting layer, and sensor-conductor junctions are sealed with a waterproof coating; the incisions are then chemically sealed. The hose cavity is filled with an insulating oil providing a continuous, oil filled constant diameter, line array hose devoid of coupling members.

Abstract: A directional velocity hydrophone is provided which does not appreciably disturb the particular movement of the fluid in which it is plunged and which comprises bending blades disposed in a ring and embedded in an inertial mass, which deliver an electric current substantially proportional to the particular speed of the fluid.

Abstract: A stacked phased array type of transducer has a single electroacoustic transducer element supported intermediately of an elongated tube having a plurality of ports and an end wall at each end thereof for transmitting and receiving acoustic waves broadside the longitudinal axis of the array tube. The element has a first vibratile surface in direct acoustical communication with the external transmission medium and a second vibratile surface in direct acoustical communication with the tube internal transmission medium. The tube is provided with at least one annular port spaced longitudinally from each end of the element for providing acoustic coupling between the internal and external transmission mediums with the tube interior providing acoustic transmission paths internally of the tube communicating between the second vibratile surface and the external transmission medium at each one of the ports.

Abstract: A shock-hardened hydrophone comprising a sensor electrically connected to a ow output-impedance preamplifier by a circuitboard. The sensor includes two metal cups, each cup with a piezoelectric ceramic disk positioned therein for generating a potential difference between the first and second surfaces of the disk. The cups are bolted together with the circuitboard positioned between the disks. The second surfaces of the disk are in pressure contact with the cups while the first surfaces are in pressure contact with a first electrode disposed on both sides of the circuitboard. A wire connects one of the metal cups to a second electrode disposed on either side of the circuitboard thereby completing the electrical connection of the disks to the electrodes on the circuitboard. The preamplifier is mounted on the circuitboard where the input to the preamplifier is the voltage difference between the first and second electrodes.

Abstract: A seismic cable assembly having an acoustically transparent tubular enclosure has at least one hydrophone electrically connected and positioned within the cable assembly enclosure. The hydrophone is made up of a pair of formed, electrically conductive plates that fit against an insulating seal which also forms a fluid seal, providing a sealed chamber defined by the inside surfaces of the conductive plates. A pair of piezoelectric elements are interconnected and positioned within the sealed chamber, one element mechanically and electrically connected to the inside surface of one of the conductive plates and the other piezoelectric element mechanically and electrically connected to the inside surface of the other conductive plate. When pressure is applied to the conductive plates, they deform, causing the piezoelectric elements to flex. When the elements flex, an electrical output is presented on the conductive plates which serve as terminals.

Abstract: An acoustically transparent hydrophone probe consisting of a rigid hoop structure in which is secured an assembly of very thin piezoelectric polymer sheet material, such as polyvinylidene fluoride, with one or more very small central sensitive portions. In its simplest form it consists of a single sheet with a small central poled piezoelectric area and with very thin metallic electrodes deposited on the sheet on opposite sides of the piezoelectric area and having fine conductive leads extending from the electrodes and adapted to be connected to a suitable amplifier or transmission line. The sheet is of biaxially stretched material, and is held taut in the hoop structure. Other embodiments may employ multiple sheets. With two sheets, the outermost surfaces are metallized and are at common ground potential, and the inner surfaces have superimposed deposited metallic electrodes with poled piezoelectric areas adjacent thereto.

Abstract: A transducer of acoustic energy through a water medium is fabricated in a manner which assures high reliability yet significantly reduces cost per unit by including modified conductive elements. A pair of flat conductors are interleaved sinuously through a ferroelectric stack in a mutually orthogonal relationship. The conductors are so interleaved as to electrically couple the elements of the ferroelectric stack in parallel in accordance with proven transducer design. At least one rod axially extends through the sandwiched ferroelectric elements and conductors to hold them in compression and to assure a reliable electrical connection for producing an integral hydroacoustically cooperating structure.

Abstract: The invention relates to underwater acoustic devices and arrays formed from such devices, and which in use are suspended in water from a buoy as other flotation equipment. An underwater device in accordance with the invention comprises an elongate tubular structure which is preferably suspended from a buoy having an aerial mounted on the buoy and connected to a radio transceiver housed within the buoy, wherein the tubular structure includes a plurality of transducer elements spaced apart along a common axis, preferably by spacer tubers wherein each of the transducer elements comprises a tube, or part of a tube, composed of a piezoelectric material, preferably polyvinylidene fluoride, and electrical terminal means contacting inner and outer curved surfaces of each tubular element.

Abstract: An ultrasound diagnosis apparatus comprising, a pulser, a transducer connected to the pulser, which is driven by drive pulses from the pulser to radiate ultrasound wave toward an object and to receive echoes returned from the object to convert the echoes into electrical signals, the thickness of the transducer changing in a direction orthogonal to the ultrasound beam traveling direction, a filter connected to the transducer for filtering the electrical echo signals from the transducer with the filter characteristic which is changed according to a change of the thickness of the transducer, signal processing circuit connected to the filter for processing the electrical echo signals passed through the filter to convert it into tomogram signal, and a monitor connected to the signal processing circuit for displaying a tomogram according to a tomogram signal from the signal processing circuit.

Abstract: The disclosure is directed to an ultrasonic transducer device that includes a plurality of layers of piezoelectric material. A plurality of conductive electrodes are disposed on the layers of piezoelectric material such that each layer of piezoelectric material has electrodes on opposing surfaces thereof. A series string of electronic delay means is provided, and has successive stages that are respectively coupled between pairs of the electrodes. An input/output terminal is coupled to an end of the series string of electronic delay means. The time delay of each electronic delay means is selected as a function of the ultrasonic wave propagation time through the piezoelectric material across which the electronic delay means is coupled. Preferably, the time delay of each electronic delay means is substantially equal to the ultrasonic wave propagation time through the piezoelectric material across which the electronic delay means is coupled.

Abstract: The radiation pattern of shaded single element piezoelectric transducers and transducer arrays has reduced side lobe levels. Shading to reduce the intensity of emitted ultrasound at the edges of the transducer relative to the center is realized by varying the electric/acoustic conversion efficiency or polarization of the piezoelectric material, by having different mechanical element lengths, by selectively poling the piezoelectric material to produce poled and unpoled regions, and by control of electrode geometry. The shading of a phased array ultrasonic transducer is described in both lateral dimensions.

Abstract: A multimode hydrophone of small diameter and low weight providing dipole ectivity patterns over a decade range of low frequencies by utilizing a pair of orthogonal dipole signals and a nondirectional reference signal to eliminate directional ambiguity. Each multimode hydrophone is a thin wall tube divided electrically into quadrants which permits differencing or opposing halves to produce signals with dipole directivity patterns and the formation of a nondirectional reference signal by summing all four quadrants. The hydrophone tube comprises inert and piezoelectric materials, selected and combined so as to shift the resonant frequency of the tube lower while keeping the over-all tube diameter as small as possible.

Abstract: A frequency independent log periodic acoustic device is utilized for the transmission or reception of underwater sound. The acoustic device when used in conjunction with any substantially plane wave receiving or transmitting transducer produces a directional, substantially constant beamwidth diffraction pattern for radiation or reception of underwater sound signals. A key element of the device is a particularly shaped plate or diaphragm, called a filter plate, made of stainless steel or other material having suitable acoustic properties. The filter plate on being placed in front of any plane wave receiving or transmitting transducer acts automatically to make the beamwidth of the diffraction pattern of the combined device constant, regardless of frequency. This is achieved by automatically making the effective aperture diameter of the filter plate-transducer combination a constant multiple of the acoustic wavelength of the sound in the underwater medium.

Abstract: A high efficiency wideband underwater transducer utilizes an axial alignment of transducer elements each employing a thin-walled radially vibrating cylinder mounted coaxially within a 45.degree. conical-shaped reflecting annulus. Each transducer element in the array is made progressively smaller in diameter so that the complete structure takes the shape of a pagoda-like assembly that fits compactly within a small size streamlined waterproof housing.

Abstract: An ultrasonic sound absorbing material capable of operating at high temperatures and pressures, said material comprises a dense, rigid, permeable material such as sintered metal filled with a viscous fluid.

Abstract: An ultrasonic transducer arrangement having a matrix of oscillators, each such ultrasonic oscillator being formed of a matrix of columnar transducer elements which are electrically controlled together. The spaces between the individual transducer elements are filled with a filler material having an acoustic impedance which substantially differs from the acoustic impedance of the ultrasonic oscillator material from which the transducer elements are formed. The ultrasonic oscillators are provided with electrode strips which are arranged in parallel rows on one flat side of the matrix. The other side of the matrix is provided with electrode strips in the form of parallel columns, so as to be transverse to the direction of the electrode strips on the first side. This arrangement permits high-packing density of the transducer elements, resulting in high resolution which enables line focusing and a close approximation of point focusing.

Abstract: This invention is a small light weight underwater transducer that operates at low frequencies. The foregoing is accomplished by embedding piezoelectric material in the wall of an oval shell between the shell's nodal points. When an alternating voltage is applied to the piezoelectric material, the piezoelectric material expands and contracts causing large circumferential strains in the shell of the transducer. The aforementioned strains cause the shell to vibrate and energy to be radiated into the water. This invention may also be used as a receiving type of transducer.

Abstract: This invention is a device that permits a flextensional transducer to function after the flextensional transducer experiences a pressure equal to or greater than the pressure found at the survival depth of prior art flextensional transducers. The foregoing is achieved by not bonding at least one end of the transducer's piezoelectric stack to the transducer's shell and having the other end or ends of the piezoelectric stack held in the vicinity of the transducer's shell by a pair of guide rails, etc. This permits the transducer's shell to move away from at least one end of the piezoelectric stack at pressures equal to or greater than the pressure at which the stack would experience tensile stresses in a conventional flextensional design. Thus, the piezoelectric stack will not fracture since it receives no tensile stress.

Abstract: A transducer made up of a plurality of piezoceramic tubes arranged in end to end relationship with elastomeric material between tubes. The tubes are poled and driven axially; however, the hoop mode of operation is utilized to obtain a fan-shaped beam extremely narrow in one direction and extremely broad in the direction perpendicular thereto. A suitable backing arrangement is provided for the transducer when mounted on a support body to prevent degradation of the beam pattern.

Abstract: An electro-mechanical transducer is disclosed in which a piston-like radiating element is driven by fluid pumped from the interior of a flextensional transducer such that the motion of the flextensional transducer shell is transmitted to the radiating element.

Abstract: The invention provides a highly focussed ultrasonic wave throughout a large depth of field without any mechanical motion. One embodiment of the invention providing two focussed fields includes a front to back arrangement of a converging lens, a transducer without any backing material to dissipate ultrasound, a converging lens, and a transducer. To focus in the far field, the front transducer transmits and receives via the front lens. To focus in the near field, the rear transducer transmits and receives via both lenses which collectively focus in the near field.

Abstract: The thinned arrayed transducer for a sonar system includes an array of sonar elements mounted in rows (layers) and columns (staves) on a structure, preferably cylindrical, to form a checkerboard pattern wherein the spacing between adjacent elements in the rows and the columns is equal to or greater than .lambda..sub.m /2, where .lambda..sub.m is the wavelength of the signal of frequency f.sub.o transmitted in the medium where the sonar is being used. The transducer structure is made from a layered cloth impregnated with a phenol based material, and includes openings in which the sonar elments are mounted. The sonar elements which are effectively a half wavelength in length consist of a cylindrical ceramic section fixed end-to-end to a cylindrical metal section. The metal section is made of a loading metal, such as brass. The transmit-receive circuitry energizes the elements by row using a modulated signal to form a variable sonar beam.

Abstract: A dual mode transducer has the capability of high power active transmission t two separate frequencies more than two octaves apart with broad bandwidth at both frequencies. The low frequency transducer is a standard double mass loaded longitudinal vibrator which has a head mass composed of a small array of high frequency transducers. The high frequency transducers are either half-wave resonators or tonpilz types. These high frequency transducers have a nodal plate mounting. The head mass of the low frequency transducer has a plurality of apertures which accept the high frequency transducers. The rear of each high frequency transducer is recessed into an aperture and has air as an acoustic pressure release. Both low and high frequency transducers form part of an electrically steerable array.

Abstract: In an ultrasonic transducer arrangement having a plurality of ultrasonic oscillators, the ultrasonic oscillators each consist of a matrix of column shaped transducer elements, which are arranged in columns and rows. A planar array which can be addressed separately is formed from a matrix of such ultrasonic oscillators. This array permits focussing of the radiated sound in its longitudinal as well as transversal direction.

Abstract: A sonar transducer especially adapted for use when subjected to high hydrostatic pressures and extreme mechanical and explosive shock. The sonar transducer includes a conventional casing, ruggedized to withstand high pressures and a hostile environment. The casing is closed on all sides but one. An array of piezoelectric ceramic stacks are suspended inside of the casing and sandwiched between a single front mass and individual rear masses. The single front mass is positioned closest to the open side of the casing. A flexible cover is sealed over the open side of the casing and pressurized oil is placed inside the housing. Appropriate channels are provided to enable the oil to freely flow throughout the interior of the unit, including flowing inside of and about the ceramic stacks. Electrical connections are made with the ceramic stacks to allow external voltages to electrically stress the stacks, and also to allow external sensing of the voltages generated when the stacks are mechanically stressed.

Abstract: A wide band, substantially constant beamwidth, frequency independent, scable acoustic array uses a mosaic pattern acoustic lens arrangement of fully directive acoustic lens antennas as the primary array antenna elements. The lenses at the center of the array pass signals at all frequencies, the lenses near but not at the center pass all signals except those at the highest frequencies and the lenses on the outer periphery pass only those signals at the lowest frequencies. When used as a transmitter, a wide band source supplies a broad band frequency signal to a plurality of filters, time delays, amplifiers, switches and acoustic retinas for applying predetermined signals to the acoustic lenses. When used as a receiver the same plurality of filters, time delays, amplifiers, switches and acoustic retinas act in a complimentary reciprocal fashion in the recovery of signals.

Abstract: A lightweight high-power transducer employs an axial array of dual-piston transducer element assemblies which are held in concentric alignment within a rigid cylindrical tube by O-rings set into grooves provided in the periphery of the pistons. The pistons have convex shaped vibratile surfaces which, in combination with the sound transmitting fluid which fills the tubular housing, causes each piston to be effectively radiating into an annular shaped tapered horn whose expanding peripheral annular area terminates into a peripheral opening placed in the circumference of the tubular housing. The combination of the inventive transducer with a tricardioid hydrophone results in a lightweight portable sonar system which achieves long-range target detection with a bearing resolution of 5.degree..

Abstract: The invention provides a highly focussed ultrasonic wave throughout a large depth of field without any mechanical motion. One embodiment of the invention providing two focussed fields includes a front to back arrangement of a converging lens, a transducer without any backing material to dissipate ultrasound, a converging lens, and a transducer. To focus in the far field, the front transducer transmits and receives via the front lens. To focus in the near field, the rear transducer transmits and receives via both lenses which collectively focus in the near field.