Abstract: In order to sense the presence of sound in a remote underwater location, a neutrally buoyant reflector (20) is deployed underwater, and a laser (12) disposed at a remote location aims coherent light at the reflector (20). A detector (24) senses the coherent light reflected from the reflector (20) and compares it in phase with coherent light split from the outgoing beam. The system then provides an indication of the presence of sound by, for instance, amplifying the result of the phase detection to a speaker (26).

Abstract: An alarm device is placed in the water of a swimming pool for monitoring the swimming pool by triggering an alarm in response to changes in water pressure or sound as a result of persons falling into the swimming pool. The device includes a switch element and wave detector, as well as an acoustic alarm. A covering device or shelf, placed below the water surface and above the detector device is an integral component of the alarm device. The covering device includes a parabolically designed wall which is placed around the detector and is in hydraulic connection with it.

Abstract: A multi-level probe for sonic range measurements utilizes a plurality of parallel reflectors that each include an opening arranged coaxially about a beam of ultrasonic energy transmitted along a reference axis from an associated transducer. The opening in each reflector permits most of the sonic energy to pass to a subsequent reflective surface, while the periphery about the opening provides echo signals for determining physical conditions in the environment through which the sonic energy has passed. A novel system is used for determining physical conditions that are a function of time differences between signals from different reflectors, calculated with a highly efficient digital signal processing algorithm.

Abstract: A conical ultrasonic wave deflection system has an ultrasonic transducer for ultrasonic microscopy using surface waves and/or Lamb waves in an object. A conical wave front is directed onto the object via a deflection element. An inactive axial circular disk is provided between the ultrasonic transducer and the object to minimize unnecessary interference from undeflected waves. A frustoconical lens with a blocked top face, or a conical metal reflector with a ring transducer on the transducer side can be provided as the deflection element. The arrangement is highly compatible with ultrasonic microscopes. Matching to a critical angle .theta. of the object is achieved by selection of the appropriate ultrasonic frequency.

Abstract: A transducer assembly which includes a plurality of staves releasably arranged around the periphery of a torpedo. Each stave includes a transducer backing member such as foam polyurethane to simulate an air backing, and a solid acoustically transparent transducer support member, such as polyurethane, disposed in front of it. A curved reflector made up of a plurality of sheets of onionskin paper is positioned between, and compressed by, the backing and transducer support members. A plurality of transducer active elements is arranged vertically within the transducer support member with the arrangement imparting a certain desired directivity pattern to receiving beams associated with such apparatus.

Abstract: A compliant tube baffle for use in a marine environment wherein a boxlike structure (10) is surrounded by an elastomeric cover (64) and includes a pair of beam plates (12,14) separated by suitable means such as bent plate springs (18,20) which may be engageable with elastic cushioning layers (54) adhered to side shields (52). The beam plates (12,14) may be tapered with the tapered sections (34) having curved surfaces in the form of an ellipse. Damping may be provided by piezoelectric elements (58) or by constrained layers (66) of elastomeric material stressed during flexing movement of the beam plates (12,14). The beam plates (72,74) may also be separated at the edges (84) by elongated members (78,80) of solid elastomer or members (92,94) of a laminate of elastomer and rigid material.

Abstract: A deep submergence, acoustically stable directional transducer uses a wavide and an encapsulant to channel sound. The waveguide forms an air space with a housing so that radiated sound is totally reflected at the air space interface. The encapsulant is matched to the acoustic impedance of the sea water at the intended operating depth to minimize reflection at the encapsulant-to-sea water interface.

Abstract: An inner decoupler for a sonar array including a linear array of hydrophones and consisting of an alternating multi-layer configuration of acoustic compliance elements in the form of acoustic baffles and acoustic non-compliance elements in the form of water or other acoustic mass-like element located between the hydrophones and the outer surface of a ship's hull. This arrangement embodies an acoustic low pass filter between the hydrophones and the hull and operates to enhance incoming signals incident to the sonar array while attenuating signals such as structure borne noise generated from the opposite or hull side of the array.

Abstract: A compliant tube baffle for use in a marine environment wherein a boxlike structure (10) is surrounded by an elastomeric cover (64) and includes a pair of beam plates (12,14) separated by suitable means such as bent plate springs (18,20) which may be engageable with elastic cushioning layers (54) adhered to side shields (52). The beam plates (12,14) may be tapered with the tapered sections (34) having curved surfaces in the form of an ellipse. Damping may be provided by piezoelectric elements (58) or by constrained layers (66) of elastomeric material stressed during flexing movement of the beam plates (12,14). The beam plates (72,74) may also be separated at the edges (84) by elongated members (78,80) of solid elastomer or members (92,94) of a laminate of elastomer and rigid material.

Abstract: The process consists in generating a primary tube wave, in using a reflecting element for the tube wave and in recording the times of emission of the induced waves radiated by the reflecting element, in receiving and recording at least part of the induced waves, then in processing the recorded signals so as to determine the characteristics of the medium to be explored. Application in particular to exploration between boreholes.

Abstract: A baffle for use in baffling or reflecting acoustic frequencies in a marine environment wherein a core ply of fiber or fabric reinforced rubber sheet is sandwiched between a pair of plies formed of an elastomeric substance and having fluid filled pockets embeddedly positioned therein in a regular, spaced relationship. The reflector functions to baffle or reflect undesired acoustic frequencies typically in conjunction with the operation of sonar arrays.

Abstract: An acoustic lens arrangement having at least one transducer for the generation and/or for the reception of a plane acoustic wavefield. The arrangement includes a focusing surface for focusing the acoustic wavefield in an object region and at least one medium for the low-loss transmission of the acoustic wavefield between a transducer, the focusing surface and the object region to be investigated. The longitudinal axis of the focusing surface is inclined relative to the direction of the normal to the acoustic wavefield in such a manner that when the longitudinal axis is positioned normal to the surface of the object region, the acoustic beams incident thereon form a critical angle .theta..sub.R with the normal to the surface of the object.

Abstract: An ultrasonic transducer and method for detecting the distance to an object using ultrasonic energy. The transducer includes a foil which creates ultrasonic energy. First and second reference surfaces are provided which are spaced between the transducer and the object. The two reference surfaces provide for immunity against temperature and positional changes.

Abstract: A method and apparatus for acoustically investigating a casing in a borehole are described. An electronically scannable acoustic transducer is formed on a planar circular surface and is oriented on a tool so as to direct circumferentially scannable beams of acoustic energy initially in an axial direction and subsequently in a radial direction onto the casing. Acoustic reflections from casing wall segments are detected and the frequencies of the casing reverberations present in the reflections are measured. One frequency measuring technique employs a reiterative technique whereby a previously measured frequency of a reflection attributable to one wall segment is used to generate a subsequent pulsed acoustic beam at the same wall segment. The number of reiterations may vary and is selected to accurately determine the thickness resonance of the casing.

Abstract: A self-calibrating ultrasonic distance sensing method and apparatus are disclosed in which a transducer periodically transmits a pair of bursts of acoustic energy along an acoustic path toward a target object. Echoes of the first acoustic burst in the burst pairs from a reference target at a known distance from the transducer are used for calibration purposes, and echoes of the second acoustic bursts in the pairs are used to determine distance to the target object.

Abstract: A spark discharge acoustic pulse transducer for borehole operation provides an insulating ceramic barrier which contains a small cross-section aperture separating two bodies of electrolyte through which the two zones of liquid make contact. An electrical arc discharge is caused to occur through the aperture to produce a transient pressure pulse and associated acoustic pulse which is coupled to the geologic formation at the borehole wall. The specific shape and geometry of the aperture channel in the insulating barrier being exponentially shaped provides a means for controlling the waveform and frequency spectrum of the acoustic pulse. The transducer has an elastic outer housing and an elastic inner housing with hydraulic fluid between the inner and outer housings. The pressure of the hydraulic fluid may be increased to expand the outer housing against a borehold prior to a spark discharge. The transducer is also provided with a system for venting gas produced as a result of the spark discharge.

Abstract: Method and apparatus for acoustic wave generation and transmission into a subsurface earth formation. A logging sonde adapted to be suspended in a borehole within the formation houses a generator means for simultaneously generating a plurality of acoustic waves traveling in the direction of and spaced substantially evenly about the logitudinal axis of the sonde. An acoustic energy reflector means within the housing reflects the waves radially outwards of the axis and into the formation at angles generally perpendicular to the axis. Detectors within the housing spaced longitudinally from the generator and reflector detect acoustic energy in the formation resulting from the reflected waves.

Abstract: An ultrasonic distance sensing method and apparatus are disclosed in which a transducer periodically transmits a pair of bursts of acoustic energy along an acoustic path toward a target object, an echo of the first acoustic burst in each burst pair is used to establish a peak reference level, and an echo of the second burst in each pair is used to determine distance to the target object only if its level exceeds a predetermined fraction of the peak reference level.

Abstract: An apparatus and method for the measuring the transverse dimensions of a hole such as in an oil well including a sonde on which an electro-acoustic transducer is mounted in an offcentered position in relation to the axis of the sonde. This transducer has two opposite active faces so as to simultaneously transmit acoustic pulses in diametrically opposite diections from the sonde. When the sonde is centered in the hole, the transducer picks up the echoes retransmitted by the wall of the hole in the two directions, at different times. A recording is made of these times and preferably also of an indication of the amplitude of each of these echoes to obtain both a diameter measurement and an indication of the condition of the hole surface. Several transducers are provided, superposed and oriented along various diameters distributed around the axis of the sonde.

Abstract: An ultrasonic transducer assembly incorporating an ultrasonic transducer and conically surfaced beam transformer wherein the conical surface of the beam transformer is mounted on the interior of closure means or end cap that seals the transducer (and any associated mechanisms) from the environment during non-operating periods and is moved into the prescribed position via rotational motion or a linear piston-like motion prior to operating periods. Suitable O-ring or gasket sealing means preserve the water tight integrity during non-operating periods and assures a seal during translational movements of the transducer assembly from operating to non-operating positions. On school buses, the beam transformer is translated to an operative position below the bus where, in conjunction with a microprocessor, it takes an accurate acoustic image before the bus door is opened and again before the bus resumes forward motion so as to detect whether students have crawled under the bus while it was stopped.

Abstract: A pressure gradient sensor is disclosed for optically sensing the direction and magnitude of an acoustic wave propagating through a fluid. Each sensor consists generally of at least three fiber-optic displacement sensors disposed within a circular array oriented perpendicular to the longitudinal axis of a streamer. Each sensor phase-modulates a coherent light signal indicative of the water pressure sensed outside the streamer. The output of the signals include a component due to transient pressure waves and a component due to hydrostatic pressure differences between the sensors.

Abstract: A sound transmitter for generation of transient acoustic pulses, comprising a spatially curved focussing emitter surface which is represented by the area of a single active or passive emitter or by the areas of several emitters matched in respect of their period of operation and amplitude. The pulses occurring in the region of the focus are generated by a substantially unipolar and chronologically limited pressure and/or velocity evolution at the emitter surface.

Abstract: Apparatus for generation of shear or compressional type vibrations within a borehole wherein oppositely oriented first and second acoustic energy sources are energized to produce output tube waves which, in turn, are equally deflected to propagate energy toward opposite sides of the borehole. Energization of the sources in-phase effects output of compressional wave energy and energization of sources 180.degree. out of phase results in shear wave generation.

Abstract: A single transducer ultrasonic distance sensor is disclosed which provides for range sensing down to zero distance from the sensor housing envelope with an electroacoustic transducer subject to unavoidable ringing following emission of a burst of acoustic energy. The housing is configured and the transducer mounted therein so that an acoustic path at least half as great as the distance travelled by an acoustic signal during the transducer ringing interval is provided within the housing envelope.

Abstract: A sonar survey apparatus comprises a submersible vessel having a structure adapted to receive a towing cable. A sonar signal transmitter is mounted on the structure. At least one acoustic reflector is mounted on the structure and is shaped to produce, in a focussing plane, line foci of acoustic echo signals received from remote positions. A line array of receiver transducers are mounted on the structure in the focussing plane and extend in a line substantially at right angles to the line foci. Each receiver transducer element has an output for providing a signal representative of a focussed echo signal. A selector is coupled with the output of each of the receiver transducer elements and has a control input and an output. The selector is operable in response to the control signal to select the output of a receiver transducer element, relating to a predetermined direction, for display.

Abstract: Navigation systems which position one or more mobile platforms in real time with appropriate accuracy in reference to a known system of coordinates by the emission of signals into a propagation medium and processing them after detection are disclosed. Broad-band, broad-beam signals are employed. All received signals convey phase encoded angular coordinate information which characterizes the particular signal path. Phase encoding of angular information is effected by suitably configured "lenses" of dispersive materials or by post-critical angle reflection from a suitably configured reflector and shield combination. When the angular coordinate information is used in conjuction with range determinations from detected signals, an especially useful navigation system is provided which can operate from a single reference station.

Abstract: An ultrasonic sensor for determining objects in air or other gaseous media is disclosed. The sensor comprises a first ultrasonic transducer having a piezoelectric transmitter. A reflector is provided having a concave surface facing the first ultrasonic transducer which forms a segment of an ellipsoid. The reflector has two focal points, the first of which is closer to the reflector and the second of which is near the object to be detected. Between the first ultrasonic transducer and the reflector, a second ultrasonic transducer is provided which is arranged at the first focal point of the reflector. Preferably, the surface of the second ultrasonic transducer facing the reflector forms a spherical segment. By this arrangement, an increase of the receiving aperture is achieved, and objects can be determined which have a normal to the reflection surface inclined with respect to the axis of the sound lobe by an object position angle which is substantially larger than .+-.3.degree..

Abstract: A low cost, efficient, ultrasonic transducer and method comprises a narrow beam electrostatic transducer and a beam transformer operated in air for expanding the emitted beam of the electrostatic transducer relative to a single axis. The beam transformer is a sonic reflecting surface spaced from the ultrasonic beam generator and within the near field thereof and having a geometric surface in which all points of said surface are generated by the revolution of a line about a fixed axis which is normal to the plane of the electrostatic transducer. A partial surface of a cone, the axis preferably being offset from the axis of the narrow beam electrostatic transducer and placed in the near field thereof transform the narrow beam to a broad beam with the beam transformer being an effective coupling element for the emitted beam and the return echo for ranging systems which are both efficient and easy to produce and do not have significant alignment problems.

Abstract: A hydroacoustic transducer provides an improved hemispherical radiation pern throughout a wide range of operating depths. A can-shaped transducer is nestled in the inside of a hat-shaped array of hollow spheres. Resiliently mounting the spheres with respect to each other and a hat-shaped shell holds the array away from the surface of the transducer and layering the hollow spheres assures the hemispherical pattern. Fashioning the spheres from hemispherical shells of aluminum and bonding them together makes the array insensitive to greater or lesser hydrostatic pressures and potting the array in polyurethane presents a more rugged structure capable of withstanding the routine abuses of the ocean environment.

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: A sonar receiver comprises an inwardly curved reflector arranged to direct received sonar signals onto a transducer system. The transducer system comprises an array of transducers distributed over an inwardly curved path facing the reflector. Each transducer is responsive to sonar signals received from a particular direction to provide an output signal indicative of a reflecting object, the amplitude of which signal is related to distance of the reflecting object.

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 apparatus and method for making wall thickness measurements. It is particularly applicable to pipeline use. It uses a pulse-echo acoustic arrangement with a single piezoelectric transducer sending and receiving acoustic signals from both faces. It has a pair of reflectors, one for each face of the transducer so that acoustic energy is directed both normal to the wall and at an angle in order to simultaneously measure the wall thickness and find any anomaly such as pitting or the like. For pipeline use there may be a plurality of instruments situated around the periphery of a unit to scan the walls as it travels through the pipeline.

Abstract: An acoustic array for use at high hydrostatic pressures comprises an acouc isolation baffle positioned adjacent to the hull; an intermediate acoustic conditioning module supported over the isolation baffle; and an outer layer containing a plurality of hydrophone units. The acoustic isolation baffle comprises alternating layers of rigid and compliant materials bonded together in sandwich fashion, wherein the compliant layer is provided with a regular pattern of air cells. In adjoining compliant layers the pattern of air cells is translated relative to each other so that the load bearing walls of one compliant layer overlap the open cell regions of the adjacent compliant layer with only a rigid layer disposed therebetween. The acoustic conditioning module comprises spaced coverplates with spacer elements extending therebetween to form a plurality of chambers which contain viscoelastic damping elements bonded to the outer coverplate.

Abstract: An underwater acoustic array comprises an acoustic skirt baffle positioned djacent to a hull surface for reducing the transmission of shipboard noise; an acoustic conditioning module positioned over the acoustic skirt baffle; and an outer layer secured to the acoustic conditioning module and containing a plurality of hydrophone units.The acoustic conditioning module comprises inner and outer spaced coverplates; a plurality of spacer elements extending between the coverplates to form a plurality of closed chambers therebetween; and "tuned" viscoelastic damping elements secured to the outer coverplate.

Abstract: The reflector of an acoustic echo ranging system is matched so as to make up for the influence of the temperature at the bottom of the reflector, on the measurement of the back-reflected signal. The acoustic signal receiver being stationary the transmission frequency is controlled by a temperature responsive electronic circuit so that the receiver is always located at the same pressure antinode. Alternatively, the transmission frequency being fixed, the position of the receiver is controlled by a temperature responsive mechanical gear causing the position of the receiver to coincide with the same pressure antinode.

Abstract: First and second reflectors, having a parabolic concave reflective surface and a conical reflecting surface, respectively, are vertically spaced on co-linear axis. An energy source, such as a loudspeaker mounted atop the frusto-conical second reflector near the apex of the conical reflective surface thereof is at or proximate the focal point of the concave reflective surface of the parabolic reflector. It is desirable for the major diameters of the reflectors to be approximately twice the wave-length of the lowest frequency sound for which the device is applicable. The shapes of the reflective surfaces are established to provide essentially equal path lengths of energy radiated from the source to a wave front to provide coherent omnidirectional energy propagation from the assembly or, in an alternative use of the apparatus, receive radiant energy and focus it on target instead of a loudspeaker at the focal point of the parabolic reflective surface.

Abstract: A curved faced, disc shaped transducer and an oppositely facing, circular angularly disposed mirror form the transmission and reception path of a mechanical sector scan imaging system. The transducer and mirror are mounted on a common axis, and a shaft upon which the mirror is affixed oscillates about that axis. Through a belt drive mechanism, a motor provides the oscillating motion, in turn scanning the ultrasound beams through the subject by virtue of the mirror motion. An optical encoder records positional information from the motor, for coordination of the mirror oscillation with transducer signals, and thereby for the assembly of a composite image.

Abstract: A device capable of operating over a wide frequency band with a constant angular width of the radiation lobe of elastic waves. It comprises in combination at least one omnidirectional reversible electroacoustic transducer and an assembly of reflecting surfaces of zero acoustic impedance which define a space inside which said transducer is arranged.

Abstract: A housing for an acoustic transducer includes means for dispersing internal reflections within the housing to minimize the incidence of such internally reflected acoustic pulses on the transducer itself, thereby avoiding the generation of spurious electrical signals for transmission to the translating circuitry.

Abstract: A nuclear reactor comprising a reactor vessel, a core housed in the reactor vessel, an ultrasonic transducer mounted in the vicinity of the upper end of the core for emitting and receiving an ultrasonic wave pulse signal propagating above the core, means for rotating the transducer by a prescribed angle to scan horizontally the ultrasonic wave emitted from the transducer, a plurality of reflective means mounted in the vicinity of the upper end of the core in a manner to face the transducer for reflecting the ultrasonic wave signal emitted from the transducer, means for energizing the transducer, and means for displaying the ultrasonic wave signal reflected by the reflective members and received by the transducer in synchronism with the wave scanning motion of the transducer, wherein each reflective member comprises reflective surfaces each capable of reflecting the incident ultrasonic wave signal in a direction parallel with the incident direction and is mounted such that the distances of the reflective surfa

Abstract: An acoustical line array transducer reflector system for producing conical hell radiation patterns. One side of the ground plane reflector of the system is covered with a chloroprene rubber-cork composition. Three transformers in ferrite cup cores are wired to the line array transducer elements.

Abstract: A reflector is disclosed, suitable for use in an apparatus for sending and/or receiving ultrasonic energy through a propagating fluid. A thin layer of ultrasonically transmissive material is disposed on a supportive substrate having an optically rough surface. A single gaseous layer is trapped between the ultrasonically transmissive layer and the substrate, the gaseous layer being contained in the asperities of the substrate layer. The substrate is preferably a metal having a roughness in the range of 1 to 10 microns.

Abstract: An underwater acoustic reflector and method for making an acoustic underwater reflector is described herein whereby electrodes are immersed in an aqueous electrolyte solution and thereafter connected to a supply of electrical current. The electrodes are selected such that bubbles form on at least one of the electrodes, providing a layer of acoustic reflective bubbles. Control of the reflectivity properties according to the intensity of the electrolyzing current is also described.

Abstract: Method and apparatus for acoustic wave generation and transmission into a subsurface earth formation. A logging sonde adapted to be suspended in a borehole within the formation houses a generator means for simultaneously generating a plurality of acoustic waves traveling in the direction of and spaced substantially evenly about the .[.logitudinal.]. .Iadd.longitudinal .Iaddend.axis of the sonde. An acoustic energy reflector means within the housing reflects the waves radially outwards of the axis and into the formation at angles generally perpendicular to the axis. Detectors within the housing spaced longitudinally from the generator and reflector detect acoustic energy in the formation resulting from the reflected waves.