Abstract: Acoustic field reconstruction is performed by expanding basis function which represent outgoing and incoming waves, without prior knowledge of the source geometry and dimensions. The reconstruction is based on acoustic pressures measured in the field only, and can be accomplished on a piece-wise basis. There are no restrictions on the locations of measurements. Moreover, the present invention can be used to reconstruct acoustic radiation from a plurality of sources or from a single source surrounded by multiple reflecting surfaces.

Abstract: A system and process for localizing signals received on multiple co-linear arrays reduces the adverse effects on localization performance due to background noise. The system and process coherently combine all possible array cross-correlograms. The resulting correlogram is a function of two variables, one which corresponds to a fine bearing estimate and a second with maps into range.

Abstract: Given a trajectory and unit pointing vectors determined based on a planar or other approximation of a shock wave, a method and apparatus are provided to calculate times the sensors should have detected, based on a conical geometry of the shock wave. A difference between the calculated times and the actual times measured by the sensors may be minimized. The minimization may be performed by perturbing the unit vectors. When the perturbation of the unit vectors results in an acceptable difference between the calculated times and the measured times, an accurate trajectory of the projectile can be generated from the perturbed unit pointing vectors.

Abstract: A firearm discharge detection device and alarm system featuring a plurality of detector units placed inside a structure which communicate with a central monitoring unit. Each detection unit will detect the discharge of a firearm in its proximity from decibel levels and duration using on board filters and timers and thereon signal the central monitoring unit. A digitized embodiment may also be used to determine the sound of a firearm using a digitized fingerprint of the sound compared to an library of firearm sounds in onboard memory by a microprocessor. The central monitoring unit will thereupon communicate with all the other detection devices installed to sound an audible and/or visible alarm to occupants to exit. Concurrently the central monitoring unit will communicate the firearm discharge and location to police. An optional directional exit alarm or warning to hide may also be activated.

Abstract: The high frequency response of a versatile exercise mine system that emulates potentially threatening mines is extended by an acoustic float system. A watertight housing is buoyed upward from the mine system and has a first acoustic sensor to provide an omni-directional response to higher frequency acoustic signals in the range of 20 to 40 kHz that are transmitted from distant sources through ambient water. A second acoustic sensor adjacent to the first acoustic sensor produces a directional response to the higher frequency acoustic signals. Processing circuits receive signals from the acoustic sensors and generate signals representative of the higher frequency omni-directional and directional responses. An inclinometer generates signals representative of inclination of the acoustic system and a cable feeds the all the representative signals to a versatile exercise mine system for additional processing and/or evaluation.

Abstract: A system which enables the position of each of a plurality of movable labelled objects to be determined in an environment having two or more isolated zones, wherein the objects carry transponders which, in response to encoded radio signals, transmit ultrasonic signals of which the transit times to a plurality of fixed receivers are determined, the transponders in the different zones being triggered in a common timeslot but in staggered relationship for one zone as compared to another, and an algorithm is applied to verify the consistency of the transit times having regard to the possible movements of objects from one zone to another.

Abstract: A system is provided in which a torpedo is launched from a submarine and pays out an optical fiber as it moves away from the submarine towards a target. The optical fiber is attached to the submarine and provides an optical communications link between the submarine and the torpedo. In addition to carrying communications between the submarine and torpedo, the optical fiber includes optical acoustic sensors. The optical fiber serves as a forward deployed acoustic array to gather target bearing and range data that is processed at the submarine. With the array deployed directly within the engagement arena, the submarine can more accurately analyze the acoustic environment to better guide the torpedo through countermeasure avoidance and to target acquisition. The optical fiber pays out behind the torpedo at the same rate that the torpedo moves away from the submarine.

Abstract: An acoustic switch, having a predetermined frequency response, is disclosed that allows for a single channel device to be interconnected to multiple transducers. The acoustic switch ensures that the signals from the transducer closest to transmitter, which has a highest possible input level, is supplied to the single channel device for processing.

Abstract: An apparatus and method for detecting acoustic signals from a plurality of acoustic signal sensors. The apparatus comprises a plurality of acoustic signal detection channels. Each channel has an input for receiving acoustic signals from a corresponding acoustic signal sensor and includes circuitry for amplifying the received acoustic signals, removing the D.C. components from the amplified acoustic signals and removing all frequency components from the amplified acoustic signals which are above a predetermined frequency. The apparatus further comprises a circuitry for summing all of the acoustic signals outputted from the acoustic signal detection channels to form a single acoustic signal and for converting the single acoustic signal into a differential signal if at least one acoustic signal sensor senses an acoustic signal and its corresponding acoustic signal detection channel outputs an acoustic signal.

Abstract: The present invention relates to an underwater apparatus, system and method for inspecting and determining the condition of a submerged structure. More particularly the present invention utilizes acoustical devices for the positioning of an inspection vehicle, with respect to the structure to be inspected.

Abstract: An ultrasonic location system for indoor environments, enabling the determination with high accuracy of the positions and orientations of objects to be tracked, wherein transmitting units (20, 22, 24) on the objects to be tracked transmit encoded ultrasonic pulses which are detected by receiver units (12 to 18) located by known positions around a room, and the receiver units are adapted to detect times-of-flight of the ultrasonic pulses in conjunction with decoding of the pulses to identify which time-of-flight applies to each transmitting unit.

Abstract: An acoustic sensing countermeasure device is used to sense the direction of a threat projectile or vehicle in addition to countering the threat with noise or interference signals. Countermeasure device includes an acoustic receive array comprised of segmented vertical staves preferably mounted within a reduced diameter section around the outside housing of the countermeasure device. The staves are grouped to form directional acoustic beams across the entire horizontal plane. To determine the direction of the acoustic signals from the threat projectile or vehicle, the countermeasure device uses a method wherein the direction is indicated by the output of the directional acoustic beams. The countermeasure device locates a known reference direction used to determine the bearing of the threat. The bearing information can be transmitted, for example, to the vessel that deployed the countermeasure.

Abstract: An apparatus and method for detecting, locating, tracking, or classifying an acoustic energy source located on a far side of a structure is disclosed. In accordance with the present invention, a receiving device samples a plurality of points on a near side of the structure to detect vibrations that result from sound waves propagated by the acoustic energy source. The location of the acoustic energy source is determined based on the relative time differences of the vibrations and the known positions of the vibrations on the structure. The acoustic energy source may be classified based on identifying characteristics of the vibrations. In addition, a device may be provided to transmit a sound wave through the structure. The receiving devices samples a plurality of points on the near side of the structure to detect vibrations resulting from reflections of the sound wave from the object.

Abstract: A system and method for a directional microphone system is disclosed. The directional microphone system can adaptively track and detect sources of sound information, and can reduce background noise. A first monolithic detection unit for detecting sound information and performing local signal processing on the detected sound information is provided. In the detection unit, an integrated transducer is provided for receiving acoustic waves and for generating sound information representative of the waves. A processor is coupled to the transducer for receiving the sound information and for performing local digital signal processing on the sound information to generate locally processed sound information. A base unit is coupled to the first monolithic detection unit and includes a global processor which receives the locally processed sound information and performs global digital signal processing on the locally processed sound information to generate globally processed sound information.

Abstract: The output signals of the acoustic sensors of the antenna are subjected to a processing of the superdirective kind, with a constraint as regards the modulus and a non-linear constraint which fixes the incoherent noise reduction.The theoretical formulation of these constraints being as follows ##EQU1## the first constraint signifying that the total transfer function is a pure delay .tau., and the second constraint signifying that a limit is fixed for the incoherent noise reduction.The antenna is provided to improve the near-field reception.

Abstract: Apparatus and methods for rapid and improved accuracy acoustic position determination comprising simultaneous and mutually distinguishable wide-band acoustic transmissions emitted from a plurality of spatially diverse transmitters and reception thereof by one or more receivers. The receivers identify the transmitters by directly (non-demodulated) correlating the received signal against stored or regenerated replicas of the transmitted signals. The location of the receiver is determined relative to the identified transmitter locations according to the measured times-of-flight from the identified transmitters to the receiver. Further embodiments of the method and apparatus of the present invention provides yaw, pitch and roll determination with a plurality of co-located receivers, and an extended and enhanced operating area.

Abstract: A method of tracking an object within a surveillance area having a predetermined linear extent. One or more ultrasound transducers are fixed to the object. A plurality of background units are placed at known positions in the area, each unit including an ultrasound transducer. One or more ultrasound waves are transmitted between the object and the plurality of background units. The ultrasound waves are received if they have propagated between the object and the background units within a time window of a duration such that the product of the duration and the speed of sound is substantially less than the linear extent of the detection area. A characteristic of the received ultrasound waves is determined, and coordinates of the object are determined responsive to the characteristic.

Abstract: A torpedo seeker head for providing guidance information in three orthogonal axes is provided according to the invention. The torpedo seeker head includes three directional hydrophones, with each directional hydrophone capable of receiving an acoustic signal and generating a signal output therefrom. The three directional hydrophones are aligned with their response axes oriented substantially orthogonally, with any two directional hydrophones and respective axes defining a plane. An omni-directional hydrophone is also provided which measures a phase of a received acoustic signal. The signal outputs from the any two directional hydrophones, in conjunction with the phase from the omni-directional hydrophone are used to calculate a look angle to a target in a plane defined by the any two hydrophones, with the measurement being substantially independent of frequency. The three directional hydrophones yield look angles in three dimensions.

Abstract: A system locates the elements of a randomly dispersed, untethered, array of sonobuoys from which are suspended active, transmitting, transducer elets and passive, receiving, transducer elements. The system comprises a data conditioning unit which receives high-frequency element-locating signals from a radio receiver, which may be located on an aircraft, and processes them so that they are quantized at its output. An acoustic delay processor, whose input is connected to the output of the data conditioning unit, correlates a reference signal R received from an active element suspended from the sonobuoy with a corresponding received signal from another element, active or passive, suspended from another sonobuoy.A position tracker, whose input is connnected to the output of the acoustic delay processor, calculates the relative position of each element of the random array from the propagation delays measured by the acoustic delay processor.

Abstract: A method and apparatus for measuring acceleration of a moving object. A body capable of transmitting pulses of energy is applied to the moving object, so as to be carried thereby and to move therewith. A pulse of the energy is transmitted in a forward direction from a first location on the body to a second location on the body at a known distance between the first and the second locations. The transmitted pulse is detected at the second location and the transit time of the pulse from the first location to the second location is measured. The measured transit time, together with the known distance between the first and the second locations, is utilized to determine the acceleration of the body and thereby of the moving object.

Abstract: A system to accurately and rapidly present the location of gunfire or other explosive events to dispatchers uses a sparse set of distributed acoustic sensors mounted on rooftops or utility poles to allow triangulation of the gunfire sounds. If a fourth signal confirms that an explosive event occurs at a position triangulated from three other signal, then the system announces an event to dispatchers. The system tests various sensor triads against various criteria and selects the best triad for making the triangulation calculation. In the case where multiple gunshots are present, the system can automatically determine a velocity, thus helping identify and respond to drive-by shootings. The system presents a confirmed location on a computer map of the protected community showing where on a specific property the gunfire occurred. The dispatchers can listen to the event and can view wave forms or spectra to assist in discriminating gunshots from other explosive events.

Abstract: This invention is an automatic gunnery system, responsive to airborne acoustic shock waves produced by a projectile passing through a target area. The invention relates specifically to the "hit" location of the said projectile for the condition when the flight path of the projectile is not perpendicular to the target area. Two pairs of concentric curved elongated acoustic energy conductors (curved sensor rods) are located adjacent to one side of said target area with acoustic transducers attached to the end portions thereof. Said transducers produce an electrical signal when a shock wave from the projectile reaches them through said energy conductors. Electrical signals from the transducers are connected to electronic circuitry and a calculating computer which calculates the intersection of two circles and determines the location of each "hit" on or near the target with each "hit" registered on a graphical display means.

Abstract: This invention discloses a method of indicating information related to the trajectory of a projectile traveling at a supersonic velocity, the trajectory intersecting a predefined target plane at a point of incidence and having an angle of incidence with the target plane, the method including sensing a shock wave generated by the projectile at a plurality of fixed locations in a vicinity of the target plane, not all of which locations lie on a single straight line, and providing a plurality of outputs responsive, respectively, to the shock wave sensed at the plurality of locations determining a time-delay for each of the plurality of locations, relative to a predefined, common, reference time, based on the plurality of outputs and determining at least one of the point of incidence, the angle of incidence and the supersonic velocity by at least estimating a solution to a set of time-delay equations, each equation providing an independent representation of only one of the time-delays as a function of the point o

Abstract: A method is described to determine the position of one or more snipers when a listening station is located in the target area, and when the snipers are randomly located. The intelligent listening system can be located at a stationary or mobile platform, consisting of a minimum of 2 microphones in the combination with a compass. The listening station registers shot sound from the sniper weapon and the shock wave from the projectile trajectory. These two signals are utilized to determine the north adjusted direction to the weapon and the shock wave. The position of the weapon is determined when utilizing the speed of the projectile and the time difference between the shot sound from the weapon and the shock wave. The position is determined as the distance along the direction vector from the listening station and to the sniper weapon. Additionally the closest distance to the trajectory of the projectile is determined.

Abstract: Three dimensional wireless pointing device for calculating coordinates and controlling a position of a cursor in a three dimensional space is disclosed, including a transmission side having a plurality of ultrasonic wave generating parts and a single infrared ray emitting part or a single ultrasonic wave generating part and a plurality of infrared ray emitting parts arranged in a certain axis direction at certain angles and a reception side having a plurality of infrared ray receiving sensors and a single ultrasonic wave receiving sensor arranged to cross the ultrasonic wave generating part(s) and the infrared ray emitting part(s) in the transmission side at a right angle, thereby to measure intensities of the infrared ray(s) and the ultrasonic wave(s) varied depending on direction of pointing and calculate a difference of relative traveling time periods of the infrared ray and the ultrasonic wave to obtain coordinate values of a position in a three dimensional space, whereby a position of cursor or menu, whi

Abstract: A coordinate input apparatus which can stably input coordinates at a high precision is provided. A vibration sensor is fixed to a vibration propagating plate by means such as an adhesion or the like. Electrodes are formed on both edge surfaces of the vibration sensor. One electrode is connected to the vibration propagating plate (its surface is made of a conductive material). Another electrode is connected to a conductive plate spring through an electrode leading member. The electrode leading member has a cylindrical portion to position a projecting portion to a center axis by setting a side surface of the vibration sensor to a reference has a relation adapted to be come into engagement with the vibration sensor. The plate spring presses the electrode leading member to the vibration sensor and is electrically connected to the vibration sensor.

Abstract: A noise detection system is provided which includes a receiving unit, a processing unit and a user interface unit connected together. The receiving unit consists of a three-dimensional acoustical array for generally simultaneously receiving a multiplicity of sound signals from different directions. The sound signals have at least one sound source of interest. The processing unit processes the sound signals and consists of a three-dimensional spatial filter for identifying the elevation and azimuth of each of the sound signals, a sound database containing a multiplicity of soundprints of sound sources of interest, apparatus for classifying the sound signals with the soundprints, and apparatus for providing the azimuth and elevation of each of the classified sound signals. The user interface unit indicates to the user the azimuths and elevations of the classified sound signals. The processing unit further consists of filtering apparatus for filtering extraneous noise signals received by the acoustical array.

Abstract: A method for reconstructing the acoustic field on the surface of a vibrating object based on measurements of the radiated acoustic pressure includes solving the Helmholtz equation directly using the expansion of a set of independent functions that are generated by the Gram-Schmidt orthonormalization with respect to the particular solutions to the Helmholtz equation. The coefficients associated with these independent functions are determined by requiring the assumed form of solution to satisfy the pressure boundary condition at the measurement points. The errors involved in these coefficients are minimized by the least squares method. Once these coefficients are specified, the acoustic pressure at any point, including the source surface, is completely determined.

Abstract: A security system for detecting a gunshot event. A communication link, and a number of pole units are arranged in a dense grid. Each one of the pole units includes a microphone and a signal conditioning and thresholding unit coupled to the microphone. The signal conditioning and thresholding unit outputs a detection signal in response to an event when an output signal from the microphone exceeds a peak background average. A data acquisition and signal processing unit is coupled to the signal conditioning and thresholding unit for discriminating gunshot events. The data acquisition and signal processing unit remains in a powered down stand-by mode so as to conserve energy until a detection signal is received. The data acquisition and signal processing unit includes apparatus for identifying a gunshot event by measuring an initial pulse time duration and subsequent pulse pattern features, and a communication interface coupled at an input to the data acquisition and signal processing unit.

Abstract: A digitizer uses acoustic waves originating from a stylus to determine the position of the stylus on a plate. The acoustic waves are introduced into the plate from the tip of the stylus and are detected by a plurality of detectors positioned at various points along the periphery of the plate. By sensing differences in the arrival times of the acoustic waves at the detectors, a microprocessor calculates the position of the stylus. In a preferred embodiment using a non-tethered stylus, four detectors are positioned at the corners of a rectangle, and the time differences are used as addresses in a lookup table, which is programmed to contain x and y coordinates corresponding to the time differences, Different embodiments may detect only the "fast" symmetrical waves or only the "slow" antisymmetrical waves generated in the plate, or may use the arrival times of both types of waves to determine the stylus position.

Abstract: A method for determining the position of seismic equipment wherein acoustic transmitters transmit spread spectrum sequences which are received by the seismic sensors in the equipment whose position has to be determined. By collecting and processing the signals thus produced, it is possible to determine the position of seismic equipment with reference to each individual sensor in the seismic equipment each time a measurement is take. The already existing conventional seismic sensors which are provided in a streamer are used to record the transmitted spread spectrum signals. By calculating time differences between the sensors' reception of a spread spectrum signal it is possible to calculate the position of the seismic equipment.

Abstract: The present invention is a system and technique for reducing the effective beam width of a receive beam for a sensing system, for example a sonar or radar system. The sensing system includes a plurality of physical sensors each for measuring a receive signal wherein each receive signal includes a first and second data processing unit. The sensing system may include means for computing sensor data for at least one extrapolated-sensor, including, first extrapolation means for computing a first extrapolated-sensor data unit of the at least one extrapolated-sensor by extrapolation of a first data processing unit of the plurality of physical sensors, and second extrapolation means for computing a second extrapolated-sensor data unit of the at least one extrapolated-sensor by extrapolation of a second data processing unit of the plurality of physical sensors.

Abstract: An underwater vehicle sonar system has sonar sensors provided in arms to plement a nose mounted array. The arms are capable of use in an extended position to provide a large diameter sonar array offering improved image resolution in the forward direction. In the extended position the arms also are capable of acting as active hydrodynamic control surfaces. Additionally, the arms can be used in a stowed position to provide a linear array for side viewing.

Abstract: A control system connected to a passive underwater transducer array is located remotely from the array, e.g. above the surface of the water, to localize an underwater source of acoustic energy in a relatively simple manner by introducing listener-motion, such as head turning or body motion of a listener, into the sound localization process and does so without any underwater mechanical linkage of any kind. This is achieved by a pair of listener-motion coupled potentiometers, referred to as mixing-pots, located at the site of the listener, being connected to the outputs of an array of passive acoustic transducers, with the two outputs of the mixing-pots being coupled to a pair of headphones worn by the listener.

Abstract: A method is described for providing an estimate of the state of a moving contact. The method comprises providing a device for estimating the state of the contact, inputting information about a location of an observer platform at particular time intervals and information from at least one sensor about a position of the moving contact relative to the observer platform at each time interval into the device, transforming the inputted information into a series of geographical grids with one grid being formed for each reading of the at least one sensor; combining grids corresponding to similar time intervals into a series of consolidated grid representations; and analyzing the series of consolidated grid representations to produce an estimate of the state of the contact at a final point in time where an observation was made.

Abstract: A method of locating an acoustic emission source in a structure by reverse ray tracing. An azimuth acoustic emission sensor is utilized which has an array of individual elemental detectors which independently and sequentially respond to the passage of an acoustic stress wave. The response of each element of the array is electronically monitored, and individual responses to the acoustic stress wave are analyzed to determine the azimuth approach angle of the wave to the azimuth acoustic emission sensor. An accurate measurement of the true location of the acoustic emission signal source is then provided by reverse ray tracing by using a parallel processing arrangement having a plurality of parallel processing elements. The structure is modeled in the computer on a one to one basis, with each parallel processing element simulating and having structural data on one discrete area of the structure.

Abstract: A security system for detecting and reporting gunshot events for control of urban environment security which includes a communication link coupled to a plurality of pole units arranged in a dense grid. Each of the plurality of pole units includes a microphone, a data acquisition unit coupled to said microphone, a signal processor for discriminating gunshot events, and a communication interface apparatus coupled at an input to the signal processor. The communication interface also has an output coupled to the communication link, where the communication interface transmits and receives data on the communication link. A central processor is coupled to the communication link so as to receive data from and transmit data to the plurality of pole units. The central processor and the plurality of pole units operate so as to detect and locate gunshot events sensed by one or more of the plurality of pole units.

Abstract: An image read-out and reproducing apparatus comprises a sub-scanning device for supporting an image storage sheet, on which image information has been recorded, and a recording material, on which an image is to be reproduced during its exposure to a light beam, such that the image storage sheet and the recording material may stand side by side with each other. The sub-scanning device conveys the image storage sheet and the recording material in the same direction or in directions opposite to each other. A single main scanning device causes a light beam to scan the image storage sheet and the recording material in a direction, which is approximately normal to the direction or directions along which the image storage sheet and the recording material are conveyed, and with a scanning width that covers both the image storage sheet and the recording material.

Abstract: The present invention is a system and technique for reducing the effective beam width of a receive beam for a sensing system, for example a sonar or radar system. The sensing system includes a plurality of physical sensors each for measuring a receive signal wherein each receive signal includes a first and second data processing unit. The sensing system may include means for computing sensor data for at least one extrapolated-sensor, including, first extrapolation means for computing a first extrapolated-sensor data unit of the at least one extrapolated-sensor by extrapolation of a first data processing unit of the plurality of physical sensors, and second extrapolation means for computing a second extrapolated-sensor data unit of the at least one extrapolated-sensor by extrapolation of a second data processing unit of the plurality of physical sensors.

Abstract: A method and system for keeping track of artillery firings of each of a ner of artillery pieces, the method including: receiving signals produced by the firings through an array of sensors, such as acoustic sensors; processing the signals to determine which of the number of artillery pieces was the source of the firing; and storing the number of firings of each of the artillery pieces. In alterative embodiments, the method further includes: processing said signals to determine the strength of each of the firings; and storing the strength of the firings of each of the artillery pieces.

Abstract: The invention relates to a device for locating noise emitters with an antenna comprising passive sensors. In a preferred variant, the antenna consists of N acoustic buoys each comprising a pair of hydrophone dipoles exhibiting a double-eight directivity diagram. Each buoy comprises a compass providing a signal K.sub.n representing the heading relative to magnetic North. The pairs of signals (a.sub.1 -b.sub.1 to a.sub.N -b.sub.N) are subjected to a rotation by the angle K.sub.n. The signals are next digitized and the number P of noise emitters estimated. The locating of these noise emitters can be performed according to two variants (8, 9).

Abstract: A method for providing detection of timing anomalies and eliminating falsely detected positions in a hyperbolic positioning system for a simulated battlefield system. The method selects a large number of transmitters for calculation of position of an object or person on the battle field. In addition, transmitters are selected which have a high dilution of precision factor.

Abstract: An object locating system, especially for use in locating a gaming ball in the game of football, utilizes a series of three sensors positioned on one side of a football playing field and a calibration source positioned on the other side. The calibration source emits an ultrasonic signal which is received by the sensors in order to provide a calibration signal. A ball marking unit is positionable on the field at a location of the ball and emits an ultrasonic signal which is received by the sensors and an RF signal which is received by the calibration source in order to turn the calibration source off. The sensors provide signals in which a processing unit calculates time delays by a time acquisition process in order to determine the position of the ball. In an alternate embodiment, the ball marking unit emits only an RF signal which is received by the sensors. The sensors again provide signals which are analyzed by the processing unit to determine delay between receipt of the signals at the sensors.

Abstract: A real time passive trajectography device comprises at least three pairs of ensors. Each pair of sensers is separated from the other pairs of sensors by a distance which is greater than the distance separating each of the sensors of the pair. One of the pairs of sensors is roughly aligned with the currently determined trajectory while other pairs of the sensors are aligned at 0.degree. to 30.degree. from the perpendicular to the current trajectory. Of each pair of sensors, the output signal from a first sensor is used as a reference signal. The output signal from a second sensor is compared to the output signal of the first signal based on a presumed speed of the object being tracked. The presumed speed is continually updated until a maximum correlation between the first and second output signals is obtained. The measurement and correlation operation is repeated at predetermined intervals, with the initial presumed speed extrapolated from the trajectory previously computed during previous intervals.

Abstract: An extendible linear sonar array for an Autonomous Underwater Vehicle (AUV) comprises a linear hydrophone array fixed in the nose of the AUV and two hydrophone array segments mounted at the leading edge of stabilization fins extendible from and retractable into the AUV. The stabilization fins are pivoted to move between extended and retracted positions where, in the extended position, the movable arrays together with the fixed nose array form a linear sonar array with extended width. In the retracted position, the stabilization fins with the hydrophone arrays pivot and fold back into stow channels in the AUV body. The stabilization fins may include movable control surfaces to control the attitude of the AUV, or the stabilization fins can be rotated when in the extended position to provide attitude control.

Abstract: An apparatus and method for determining the range and depth to an acoustic ource from a sampling site in a medium. A linear array of pressure transducers monitors the acoustic field produced by the acoustic source. A measurement processor utilizes the measured acoustic field to produce an initial field condition for each member of the array. An environmental model includes environmental data in the form of acoustically pertinent variables that define acoustic energy transfer characteristics through the medium at different ranges and depths. A backpropagation processor utilizes the initial field condition and the acoustically pertinent variables to produce, for each incremental range and depth, an amplitude function. An index processor normalizes the amplitude functions for each incremental range and depth, and an index extreme value processor selects the amplitude function with the maximum amplitude.

Abstract: The present invention is an electro acoustic target searching system comprising receiving transducer means capable of receiving first, second and third frequencies, signal evaluation means for producing direction signals indicative of direction of reception of acoustic signals at any of the frequencies and logic means operable to control the frequency at which the evaluation means determines the direction of reception so that if a direction signal determined from evaluation at the lowest frequency exceeds a reference magnitude, evaluation is then made at the middle frequency, and if the resulting direction signals indicate receipt of acoustic signals exceeding a predetermined magnitude from a plurality of directions, evaluation is made at the highest frequency.

Abstract: An underwater location system (16) is disclosed having a plurality of locator modules (18), each capable of finding the relative range and bearing of other modules. The modules may be diver mounted, placed on movable objects such as a boat (14) or on fixed positions such as the sea floor (12). Range and bearing to each module of the system is displayed, upon request, on a console (20) which may be hand held or mounted in a diver's instrument console. Each module can interrogate other modules with an acoustic pulse which is answered, after a unique time delay stored in each module, by an acoustic response pulse. Response pulse sources are identified by their arrival in a time detection window set by their unique time delay. Range to each identified transponder source is calculated from a receipt time within each detection window.

Abstract: A method is provided for detecting and localizing acoustic sources. Acous signals are transmitted by a sonobuoy and return signals are received. Electrical signals, corresponding to the received return signals, are multiplexed and transmitted. The transmitted signals are received by a receiver which is separated from the transmitter. The receiver applies the received signal to a demultiplexer which is separate from the the receiver. The demultiplexer demultiplexes the applied signals to provide electrical signals to the cardioid beamformer representative of the sonar return signals.

Abstract: By incorporating a Global Positioning System (GPS) receiver into the electronics of an active or passive sonobuoy for determining a geoposition of each sonobuoy comprising an array of sonobuoys or a sonobuoy field, the position of each sonobuoy can be ascertained as the original position of the line of sonobuoys forming the array changes due to wind, sea state and currents. The GPS geoposition of the individual sonobuoys is transmitted to as receiving vehicle along with the acoustic signal obtained by the sonobuoy sensor. Utilizing an onboard computer, the receiving vehicle can compute a synthesized coherent array position. The military P(Y) code transmitted by the GPS satellites is utilized to determine the geoposition of the sonobuoy relative to the other sonobuoys to a degree of accuracy of 2 to 3 meters.