Abstract: A flextensional sonar transducer may comprise an elliptical shell which, during manufacture of the transducer, has been distorted to permit insertion of stacks of piezo-electric ceramic plates and then released to grip the stacks and maintain them in compression, even when at design depth. The distortion requires substantial loading and may damage the shell. Herein, the undistorted shell is fitted with the ceramic plate stacks and an adjustable wedge device which is settable to provide the required pre-load. The wedge device may be coupled to an actuator, pressure sensor combination which automatically maintains a desired pre-load for different depths.

Abstract: An acoustic transducer, especially adapted for hydrophones, is disclosed. The transducer comprises a piezoelectric ceramic disk with a main or signal electrode, a common electrode and a feedback electrode; negative feedback is provided around an associated amplifier and the transducer. The transducer is useful in either a sonic receiver or a sonic transmitter. Various ceramic disk configurations are disclosed and several electrode configurations are disclosed. The negative feedback minimizes the undesired effects of the high Q characteristic of the piezoelectric ceramic transducer. The transducer exhibits improved frequency response characteristics including increased bandwidth and reduced resonance effects, fixed or linear phase shift over a broad range and improved transient response. Also, the effect of normal manufacturing variations upon sensitivity, frequency and phase response is minimized.

Abstract: The insulation resistance between the electroded surfaces of an underwater transducer and the water within which the transducer is immersed is greatly improved by coating the electroded surface of the transducer with a layer of air-free, high-resistance waterproof material before bonding an elastomer covering over the assembly to serve as the outer housing.

Abstract: An underwater acoustic wave transmitting and receiving unit having excellent characteristics for both transmitting and receiving and providing stable characteristics over long operating periods. A plate-shaped polarized piezoelectric resonator is provided formed of at least one plate made of a complex of fluorosilicon rubber and lead titanate. The resonator is sealed in a rubber casing filled with an insulating liquid matching the water around the casing in acoustic impedance.

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 phase and amplitude compensated surface acoustic wave (SAW) structure is described in which computer controlled compensation is achieved by laser chemical etching of selective portions of a compound chemical film deposited on the surface of a piezoelectric SAW substrate in the path of propagation. The compound film comprises a layer of amplitude attenuating cermet material formed on the substrate and a phase compensating layer of molybdenum formed over the cermet material and in contact with the substrate surface.

Abstract: An ultrasonic transducer comprises a support body, a piezoelectric layer of a material with a relatively high dielectric constant and high acoustic impedance, a first impedance matching layer and a second impedance matching layer (10). The first matching layer consists of silicon.

Abstract: A plurality of piezoelectric or magnetostrictive rectangular planar staves are held in side-by-side relation in a laminate assembly including insulative spacers. The widthwise polarity of adjacent pairs of the staves are inverted relative to each other. The acoustic centers of the staves are spaced apart a distance of approximately one-half of a wavelength of the operating frequency. Electrical connections are made to the opposite side edges of each of the staves through leads and bus wires. The array of staves define an active planar acoustic face for simultaneously sending and simultaneously receiving a pair of angularly separated beams of acoustic energy without electronically phasing or time delaying the signals transmitted to and from the individual staves and without mechanically rotating the array.

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: The preferred embodiment of this invention includes a logging sonde, an elongated pair of oppositely polarized piezoelectric plates connected to each other by their flat surfaces, and an electrical pulse applying means for applying electrical pulses across the pair of plates so as to bend and vibrate the plates in a direction perpendicular to the length of the plates. Vibration of the plates in a fluid contained in a well creates in the fluid a positive compressional wave in one direction and simultaneously a negative compressional wave in the opposite direction. The two compressional waves will interfere to produce a dipole shear wave in the earth surrounding the well. The dipole shear wave arrival is detected at two locations in the fluid spaced longitudinally along the well from each other and from the plate.

Abstract: An ice detector to detect a lyaer of ice on a thin solid sheet 14, such as the skin of an aircraft wing, even in the presence of water, comprises two ultrasonic transducers attached to the sheet. The first transducer 10 is adapted to cause propagation of ultrasonic waves through the sheet 14 having their predominant component parallel to the surface of the sheet 14. Such waves will dissipate energy into an ice layer adhering to the surface, but not into air or a liquid layer. The second transducer 30 is adapted to detect the waves propagating in the sheet and to give a signal representative of their amplitude. A discriminator 34 responsive to the signal detects the presence of an ice layer on the surface.

Abstract: A piezoelectric speaker comprises a piezoelectric vibrator (1) for vibrating in a bending mode, which is supported at its longitudinal intermediate position by a support member (6), whereby first and second portions (1a, 1b) of the piezoelectric vibrator (1) on both sides of the support member (6) are respectively supported in a cantilever manner. The piezoelectric vibrator (1) is connected at portions close to both ends thereof with a diaphragm (8) by coupling members (12) formed by wires, whereby bending vibration of the piezoelectric vibrator (1) is transferred to the diaphragm (8) thereby to drive the diaphragm (8).

Abstract: A swimming pool alarm consists of a sensor suspended beneath the water surface of the pool, including an electrical resonator element and a captive element agitatable by the pool water adjacent the resonator element, and an alarm device external of the pool which responds to the amplitude of resonance of the resonator element exceeding a certain level.

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: An ultrasonic transducer consisting of three piezoelectric element couples sandwiched between four metal terminals. Each piezoelectric couple has two piezoelectric elements separated by an electrode. The piezoelectric couples and the metal terminals are secured together by a bolt. The transducer exhibits various combinations of resonant frequencies in its impedance-frequency characteristic as determined between various combinations of the electrodes and terminals.

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 improved ultrasonic transducer that can be used for cleaning the inner wall surface of water-filled tank, such as a toilet bowl, employs a ceramic disc operating in the planar resonant frequency mode in combination with an acoustic transmission line comprising a solid washer-like annulus bonded to the periphery of the ceramic. The radial dimension of the annulus is made equal to approximately one-half wavelength of sound in the material at the frequency of operation. The annulus serves as an acoustic transmission line to extend the peripheral vibrating surface of the ceramic so that the acoustic power is transferred from the periphery of the ceramic disc to a region closer to the inner wall surface of the tank. The transmission line also increases the radiating area of the transducer element which achieves increased sonic power density in the vicinity of the wall surface.

Abstract: A twin-transducer seismic detector includes a hollow housing closed at each end by a diaphragm-type transducer. A deformable retaining member is pressed against the perimeter of each transducer. An adjustable force is applied to at least one of the deformable members to cause the member to flatten against the transducer. As the deformable member becomes flattened, it reduces the effective area of the transducer and hence alters its compliance and sensitivity. The applied force is adjusted so as to match the sensitivity of one transducer to that of the other transducer.

Abstract: A piezoelectric polymer hydrophone including a single flexible sheet of a ezoelectric polymer having a plurality of electrode strips on the top and bottom of the sheet. The electrode strips at the top are staggered by one half the width of a strip relative to the corresponding strips at the bottom of the sheet. The polymer sheet can be rolled into a helix without losing its acoustic sensitivity.

Abstract: An ultrasonic wave transducer is formed from a body of piezoelectric material having nonuniform thickness. Each location on the transducer is resonant at a different frequency according to the thickness at that point. By changing the frequency of the applied excitation signal, the origin and direction of the radiation can be altered.

Abstract: An ultrasonic transducer comprises an acoustic wave propagation medium, a piezoelectric element mounted on one surface of the propagation medium, and an ultrasonic lens formed in the opposite surface of the propagation medium and having a predetermined focal distance. The ultrasonic radiation generated from the piezoelectric element is propagated through the propagation medium and focused by the lens. The axial length of the propagation medium is selected to be 1/N (N: odd number) of a Fresnel focal distance.

Abstract: An air gun firing sensor apparatus and system are provided for determining the instant of firing of an air gun by sensing pressure changes within the air gun when it is being fired. A pressure-change-sensitive transducer assembly is inserted into a socket in the housing of a solenoid-controlled valve of an air gun with a passage from the air gun communicating with the transducer for transmitting to the transducer a pressure surge occurring within the air gun whenever it is fired. The transducer assembly has a cylindrical casing with a head mounted at one end. The head includes a plurality of spaced recesses which are adapted to communicate with the passage leading from the air gun.

Abstract: An improved transducer for generating and detecting shear waves using pielectric bimorph elements. A plurality of pairs of bimorph elements are formed by rigidly attaching together two individual lengths of piezoelectric material with each dimensioned to provide a length and width substantially greater than its thickness. The plurality of bimorph pairs are mounted in a configuration such that each pair is separated by a layer of high compliance material with the electrical polarization of each piezoelectric element pointing in the same direction. Electrical potential applied simultaneously to the electrodes of the individual pairs causes the entire end face of the transducer to perform a shearing motion which will generate or detect acoustic waves in materials in contact with the face.

Abstract: An integrating hydrophone sensing element is provided having improved sensitivity and capability of withstanding high pressures. The sensing element consists of a rigid cylinder with semicylindrical sensing surfaces rigidly connected to the cylinder at diametrically-opposite points. A membrane of piezoelectric polymer material extends diametrically across the cylinder and is attached to the cylinder at points displaced 90.degree. from the connections of the sensing surfaces. Vibration of the cylinder by acoustic signals transmitted from the sensing surfaces causes vibration of the membrane and produces an electrical output signal.