Abstract: A method and apparatus for measuring the depth of fluid in a well and for controlling the speed of a pump which pumps fluid out of the well according to the measured depth is disclosed. The depth of fluid in a well is measured by sending an acoustic pulse into an annulus between the well casing and the production tubing and sensing reflections of the acoustic pulse from collars on the tubing and a reflection from the fluid surface. Since the collar spacing on the production tubing is known, the distance from the top of the well to the surface of the fluid can be obtained by accumulating the distance associated with the collars detected in the reflection signal. The collar reflections are sensed by converting the reflected acoustic wave into electrical signals and then amplitude demodulating the broadband electrical signals.

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 finding the direction of a wave source using an array of sensors. The system includes a sensor array for measuring waves from the wave source, an approximate-direction finder for finding the approximate direction of the wave source in terms of a sensor pair from the sensors, a precise-direction finder for finding the precise direction of the wave source based on the approximate direction found, and a measurement qualification unit for evaluating the validity of the precise direction under a measurement criterion and discarding the measurements if the criterion is not met.

Abstract: A system for detecting gunshots includes an input device including a microphone for converting acoustic noises into signals and amplifiers for amplifying the input signals, a threshold detector for receiving the amplified signals and comparing the signals with a predetermined threshold value and for producing an output signal when the threshold value is exceeded. A pulse width detector is connected to the threshold detector for producing an output signal only if the width of the threshold detector output signal is within a predetermined range of values. A pulse count detector is also connected to the threshold detector for producing an output signal when the level of the threshold output signal is above a peak threshold level or the number of threshold level output signals that exceed a threshold level are less than a preset limit. An output device indicates that a gunshot has occurred only when signals are received from the pulse width detector and the pulse count detector during a sampling period.

Abstract: A method of correcting errors in in inertial navigation system, without imposing restrictions on the ships course, utilizing bathymetric data collected during the Ocean Survey Program (OSP). As the ship is in transit in or crosses an OSP swath, sonar transmissions commence and continue only to acquire bottom data within data areas of predetermined dimensions. Depth gates and transmission power levels are established in accordance with OSP provided bottom data and depth is determined by an autocorrelation process. A virtual linear map is established with the OSP data in the predicted locations of data collection areas. The collected data is then compared to corresponding OSP data to determine inertial navigation system corrections.

Abstract: An apparatus and method for determining directionality of acoustic signals arriving from an acoustic source is disclosed. A plurality of reflectors for modifying the acoustic signals and a transducer located proximate to the reflectors is used. A notch detector detects and identifies spectral notches in the modified acoustic signals. A device then determines the direction of the acoustic source. In one embodiment, a microphone system capable of detecting three-dimensional sound is provided. The microphone system comprises an elliptical-shaped microphone enhancer having at least two reflectors located different distances apart from a microphone located in the center of the ellipse. The reflectors have asymmetric ridges which cause interference patterns in the signals received by the microphone, conceptually analogous to the patterns generated by the pinnae of the human ear.

Abstract: An optical recording/reproducing apparatus includes an irradiation optical system for irradiating a light beam from a light source onto a predetermined track of an optical recording medium having a plurality of neighboring tracks as a fine light spot so as to perform recording/reproduction of information or reproduction of information, and a detection optical system for detecting a returned light beam from the optical recording medium. A mask is arranged in a far field region sufficiently separated from a focal plane of the detection optical system, for masking marginal rays, in a direction perpendicular to the track, of the returned light beam, so that information reproduced from a track adjacent to the predetermined track upon reproduction of information on the predetermined track is reduced.

Abstract: A swimming pool alarm system including a plurality of motion sensors positioned around a periphery of a swimming pool in a spaced relationship. The plurality of motion sensors generate a sensor beam that extends around the periphery of the swimming pool. An alarm horn is positionable within a house adjacent to the swimming pool. The alarm horn is couplable to an electrical outlet. The alarm horn is in communication with the motion sensors. A portable alarm mechanism is positionable on a body of a pool owner. The portable alarm mechanism is in communication with the motion sensors.

Abstract: A position tracking system comprises a transmitter at a first location for producing a signal and an array of plural ultrasonic transducers at a second location arranged in a grid pattern at a plurality of respective discrete locations. The plural ultrasonic transducers are responsive to the signal to produce plural reactive signals corresponding to the signal as received at respective ones of the plural ultrasonic transducers. A computer is responsive to the reactive signals from the plural ultrasonic transducers for continuously determining the position of the array. The ultrasonic transducers are physically separated.The ultrasonic transducers and spatial light modulators share a common backplane.

Abstract: A system for detecting gunshots includes an input device including a microne for converting acoustic noises into signals and amplifiers for amplifying the input signals, a threshold detector for receiving the amplified signals and comparing the signals with a predetermined threshold value and for producing an output signal when the threshold value is exceeded. A pulse width detector is connected to the threshold detector for producing an output signal only if the width of the threshold detector output signal is within a predetermined range of values. A pulse count detector is also connected to the threshold detector for producing an output signal when the level of the threshold output signal is above a peak threshold level or the number of threshold level output signals that exceed a threshold level are less than a preset limit. An output device indicates that a gunshot has occurred only when signals are received from the pulse width detector and the pulse count detector during a sampling period.

Abstract: The position of an object is tracked underwater. Prior to tracking, the object is tagged with an acoustic transmitter. It is important that the transmitter emits sound waves having a frequency of at least 200 kilohertz (kHz) because it has been found that these transmitter frequencies provide better tracking data in noisy environments than conventional transmitters operating at 50-60 kHz. The acoustic transmitter is located by a split-beam transmitter. The position of the object can be accurately tracked by using two split-beam transducers, synchronization of transducer and transmitter, or echo ranging.

Abstract: The present invention relates to radars and sonars, and more particularly to a synthetic-band technique of pulse compression making it possible to reach a very high distance resolution. Synthetic band consists in transmitting a waveform pattern consisting of a string of N coherent elementary pulses, linearly frequency-modulated, following one another at a recurrence frequency F.sub.r, of rectangular frequency spectra of elementary band B and of stepped carrier frequencies such that their frequency spectra will link up exactly one ahead of another to form a global spectrum of width N.times.B. On reception, the frequency spectra of the signals received in return for the N elementary pulses of a pattern are extracted by calculation, translated and juxtaposed so as to reconstruct a global frequency spectrum of width N.times.B and then compressed. Pulse compression is thus obtained which is equivalent to that which would result from the transmission of a waveform having a single pulse of frequency band N.times.

Abstract: A method of bearing estimation comprising quadrature digital filtering of event observations, constructing a plurality of observation matrices each centered on a time-frequency interval, determining for each observation matrix a parameter such as degree of polarization, linearity of particle motion, degree of dyadicy, or signal-to-noise ratio, choosing observation matrices most likely to produce a set of best available bearing estimates, and estimating a bearing for each observation matrix of the chosen set.

Abstract: An object detecting apparatus includes at least one transmitter and receiver pair having a transmitter for transmitting waves and a receiver for detecting reflected waves caused by objects reflecting the transmitted waves. The receiver outputs reflected wave detected signals in response to detecting reflected waves. A control unit is connected to the at least one transmitter and receiver pair for providing transmit control signals to the transmitter and for receiving and evaluating the reflected wave detected signals from the receiver. The control unit also determines a distance between the receiver and the object. There is also provided at least one speaker connected to the control unit for providing an audible signal.

Abstract: An aiming point system and technique for defining the aiming point of a d collection receiver used by an operator. A data receiver is directed to the aiming point for collecting and amplifying sub-audio signals emitted from rotary aircraft. The sub-audio signals are converted to audible signals by a voltage to frequency converter. The aiming point is readjusted manually or automatically in response to the sub-audible strength of the audible signal to obtain at least a substantial proportion of the target signature of the rotary type aircraft. The data collection receiver may include binoculars with a silicon photo detector and pre-amp within one of the binocular eyepieces.

Abstract: An elastic wave position-sensing device comprising a piezoelectric substrate, an input interdigital transducer T formed on an upper end surface of the piezoelectric substrate, and an output interdigital transducer R formed on the upper end surface of the piezoelectric substrate such that the finger direction of the interdigital transducer R is slanting to that of the interdigital transducer T by an angle .alpha.. The thickness d of the piezoelectric substrate is smaller than an interdigital periodicity P of the interdigital transducer T. An interdigital periodicity P.sub.N along the vertical direction to the finger direction of the interdigital transducer R is equal to the product of the interdigital periodicity P and cos .alpha.. An overlap length L.sub.P along the finger direction of the interdigital transducer R is equal to the product of an overlap length L of the interdigital transducer T and sec .alpha..

Abstract: A covert aircraft detection system for a submarine is described which inces an acoustic antenna array and a signal processor to process the acoustic signals to provide the location of the detected aircraft and to classify the detected aircraft. The acoustic antenna array is mounted on the submarine mast and includes a vertically extending rod having a microphone and connected thereto three or more folding legs having microphones connected thereto. The microphones detect the aircraft acoustic signals and these signals are transferred to the signal processor which provides the location of the aircraft and matches the acoustic signal with the database of aircraft acoustic signals to classify the type of aircraft. When the acoustic antenna array is connected to a rotatable mast, such as a periscope, a rotary encoder and mast bearing indicator are utilized to account for the rotation of the acoustic antenna array and the rotation of the mast, respectively.

Abstract: This invention is in the field of underwater ultrasonic communications systems, more particularly, underwater acoustic homing devices suitable for diver direction finding. This invention utilizes a single omnidirectional sound source and a simple receiver, located in close proximity to a scuba diver's torso and equipment. The acoustic discontinuity of the diver's torso and equipment provides the required directional sensitivity, thus allowing the device to incorporate the desirable characteristics of flexibility in range in combination with a simple receiver housing.

Abstract: A process and a device for detecting objects, in particular mines, dispersed in an area of land, or for determining propagation characteristics of an acoustic wave in the ground of an area of land. This process employs a plurality of acoustic transducers and reference targets distributed along borders of the area. After determining an optimal working frequency, a cartography of the propagation characteristics in the ground of the area of land is made, for example, by carrying out several temporal reversals, one after the other, of the signals received by the transducers so as to focus detection on the different reference targets. Objects are detected with the aid of this cartography by focusing detection by temporal reversal on an object and by searching for at least two transducers which have the lowest propagation time for the signal.

Abstract: On Fork Lift 100, Load Cell Assemblies 40a and 40b are affixed to Fork Arms 32a and 32b and as such are capable of determining the weight of any object lifted by Fork Arm Lift Assembly 30. Continuous weight information is transmitted from Assemblies 40a and 40b to Fork Lift Computer 52 via wires and IR Transmitter 44 and Receiver 48. Changes in weight information are interpreted as load engagement and disengagement by Computer 52, which then responds by receiving the current relative vertical height of Fork Arm Lift Assembly 30 from Ultrasonic Distance Measuring Unit 56. The Computer 52 then transmits, via Telescoping Antenna 70, an uniquely encoded signal with both weight and height information to Stationary Elevated Locating Modules such as 74a and 74b, which have been strategically placed throughout the operating range of Fork Lift 100. This signal is then transmitted to Unit Tracking Computer System 80 by Locating Modules such as 74a and 74b.

Abstract: A series of pulses of ultrasonic wave emitted from the transmitter with a specified period are received by the receiver. The received signals are rectified to a smooth wave with a single peak. The occurrence time of the peak is determined to gain and store the peak value, which corresponds to the edge position, thickness or splice position of the web. Alternatively, the transmitter emits a series of pulses of ultrasonic wave with a specified period and the peak value in the signals received by the receiver is once held in the peak-holding circuit. The peak voltage held is discharged and reduced with the discharge device and smoothing of the charged voltage yields its mean value, which corresponds to the edge position, thickness or splice position of the web.

Abstract: A navigational device (10) for assisting a scuba diver in determining a direction toward and a distance from a dive boat (12) or to a buoy near the shore at which point the dive originated. The navigational device (10) includes a transponder unit (16) carried by a boat (12) and an interrogator unit (34) carried by a diver. The interrogator unit (34) includes at least one transducer (68) positioned for detecting signals from the transponder unit (16). Direction and distance indicators (46,50) are carried on the surface of the interrogator unit (34) for visual indication to the diver. The transponder unit (16) repeatedly pulses an identification signal to be received by the interrogator unit (34). When a valid identification signal is received by the interrogator unit (34), the direction from which the signal was received is determined and displayed. When the distance to the boat (12) is required, a signal is emitted from the interrogator unit (34).

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 and apparatus for passively determining the range of a radiating source that is in a state of motion with respect to an observer. In one embodiment of the invention the range is determined in accordance with the bearing rate of the radiating source, the bearing acceleration of the radiating source, the frequency of the received radiation, the frequency rate of the received radiation, and the velocity of the radiation through a medium. In another embodiment of the invention the range is determined in accordance with the bearing rate of the radiating source, the bearing acceleration of the radiating source, the fractional frequency rate of the received radiation, and the velocity of the radiation through the medium.

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 method and apparatus for detecting, processing and tracking sonar signals o provide bearing, range and depth information that locates an object in three-dimensional underwater space. An inverse beamformer utilizes signals from a towed horizontal array of hydrophones to estimate a bearing to a possible object. A matched field processor receives measured covariance matrix data based upon signals from the hydrophones and signals from a propagation model. An eight nearest neighbor peak picker provides plane wave peaks in response to output beam levels from the matched processor. A five-dimensional M of N tracker identifies peaks within the specified limit of frequency, bearing change over time, range and depth to specify an object as a target and to display its relative range and depth with respect to the array of hydrophones.

Abstract: A trajectory estimation system for estimating a trajectory of a target in sponse to a series of data items which generated in response to motion of the target. The trajectory estimation system includes a data segmentation means and a trajectory selection means. The data segmentation means processes the series of data items in accordance with a regression/multiple-hypothesis methodology to generate a plurality of segments, each having associated data items which have similar features. The trajectory selection means for processing said segments in accordance with a multiple-model hypothesis methodology to generate a corresponding statistically-supportable candidate trajectory motion estimate of target motion thereby to provide indicia of an overall trajectory of the target.

Abstract: The detection of a microphone within a selected site includes broadcasting an acoustic signal having two components with different frequencies selected to produce the re-broadcast, by a microphone in the broadcast field, of a selected resonant responsive signal, and sensing the re-broadcast of such a responsive signal. Determining the direction in which such a responsive signal is sensed determines the location of a microphone detected to be present within the selected site.

Abstract: A system for automatically detecting the event of a person or object falling overboard from a vessel into water includes a portable ultrasonic transmitter worn by each person or attached to selected objects on board and designed to be activated upon immersion in water, and an alarm control unit carried by the vessel containing an ultrasonic receiver. When the receiver detects a signal produced by a portable transmitter, it sounds an alarm and displays the vector velocity of the vessel relative to the portable transmitter, allowing rescue operations to be initiated and carried out even in conditions of zero visibility.

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: 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: Two geophones located above an underground pipeline are spaced from each other and adjacent to both sides of a benchmark location. As a pig travels through the pipeline sound waves are generated. As a pig approaches a benchmark location, sound waves are received first by the geophone which is closest to the source of the sound waves, that is, the upstream geophone and then by the downstream geophone. The geophones generate electrical signals that are fed to a comparator circuit which is connected to upstream and downstream indicators, one of which is activated when a pig passes the benchmark depending on whether the sound was first received by the upstream or downstream geophone. An alternate embodiment adds a magnetometer at the benchmark location capable of sensing changes in the ambient magnetic field caused by the passage of a pig.

Abstract: A fabrication of a shim for insertion within a gap extending in two orthogonal directions between two structural members in the building of a mechanical structure is accomplished by measuring the gap to provide a map of gap width. Variations in gap width appear in the map so as to enable machining of the shim with corresponding variations in thickness so as to fit accurately in the gap. Measurement of the gap width is attained by use of two acousto-electric transducer assemblies, each of which is constructed as an array of electrode discs produced by photolithography upon a flexible, electrically-insulating film of piezoelectric material which serves as a substrate for support of electrodes on a front surface thereof and a ground plane structure on a back surface thereof. The two transducer assemblies are secured adhesively to corresponding surfaces of structural members defining the gap, and an acoustically-transmissive gel is disposed between the two transducer assemblies.

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: 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: 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: A sensor for detecting acoustic energy emitted by a target is disclosed. The sensor comprises a housing including a plurality of transducers for receiving acoustic energy. The transducers are randomly deployed within a predetermined area around the housing, forming an array and a self-survey technique is utilized to determine the positions of the sensors. Beamforming techniques are utilized to analyze the acoustic energy detected by the transducers to provide the azimuth of a target and a class estimate of the target. A plurality of sensors may be utilized to provide target location, course and velocity.

Abstract: An array of transducer elements receives energy from a target or targets in a field of view and operates on the transducer outputs to provide a plurality of different levels of shading. The most useful portion of the field pattern is selected and combined with other most useful portions of other field patterns into a single composite display which results in one or more relatively narrow lobes, indicating targets, and without the presentation of side lobes which may be masking targets.

Abstract: A diver navigation system which provides reliable position information to able a diver to locate and when required repair existing underwater devices such as cables, leg moorings and the like. The diver navigation system comprises a synchronous range-range navigation system operating on a repeating timing cycle, which is accurately duplicated in a master transmitter, a slave transmitter and a receiver. Within the master and slave transmitter the timing cycle is subdivided into two equal approximately one second subcycles, the first subcycle being for the master transmitter and the second subcycle being for the slave transmitter. The master transmitter sends out a tone burst signal at the beginning of the first subcycle and the slave transmitter sends out a tone burst signal at the beginning of the second subcycle. Each tone burst signal, in turn, comprises a 34 kilohertz signal followed by a 32 kilohertz signal each of which has a time period of approximately one millisecond.

Abstract: A system and method of indirect underwater acoustic ocean surveillance is sclosed requiring at least two sonar platforms, usually ships, travelling some distance apart. At least one of the platforms transmits sonar pulses, portions of which are scattered off the ocean floor to at least one companion sonar receiver platform. The receiver platform is provided with means to analyze the received scattered sonic pulses to determine if a submerged object such as a submarine is obstructing a portion of the pulse, thus casting an acoustic shadow. With accurate positioning information supplied by a navigation information system such as the NAVSTAR GLOBAL POSITIONING SYSTEM (GPS), and by combining pulse measurements over several positions the system will be able to locate, identify, and track the obstructing object by analyzing these acoustic shadows or silhouettes. Geometric silhouette reconstruction techniques and other mathematical techniques may be employed to construct an image of the submerged object.

Abstract: A safety system for deterring a homing missile from attacking its launching ehicle whereby the launching vessel is enabled to alter the course and neutralize the detonator of the weapon.

Abstract: An apparatus and method for detecting, processing, and tracking sonar sigs is provided. Plane wave energy from the sonar signal source is measured at multiple points using an array of plane wave energy receptors. These measurements are processed using an inverse beamformer to generate output beam levels. These output beam levels are then processed using the spectrum normalizer to yield spatially and spectrally normalized output beam levels. The normalized beam levels are then processed using an eight nearest-neighbor peak-picker to provide plane wave peaks. Finally, the plane wave peaks are processed by a three-dimensioned M of N tracker to identify peaks within a specified limit of frequency and angle change over time. The identified peaks may be displaced or recorded for further analysis.

Abstract: An apparatus for detecting a person in a body of water includes a transmitter for generating an electrical swept frequency signal having a frequency that continuously varies between upper and lower limits, at least one pair of transducers disposed in a body of water including a transmitting transducer connected to receive the swept frequency signal for launching a beam of acoustical waves in response to the swept frequency signal in the body of water and a receiving transducer disposed opposite the transmitting transducer for receiving the acoustical waves and for converting received acoustical waves into an electrical received signal, and a receiver connected to the receiving transducer for producing a detected signal in response to the received signal, for producing a threshold signal in response to the detected signal, and for initiating an alarm when the detected signal falls below the threshold for at least a predetermined length of time.

Abstract: Aquatic animal detector apparatus is constituted by a passive transducer for converting sounds, including bio-soundwaves from a living source traveling in a body of water, to electrical signals. A resonance chamber is connected to said transducer and tuned to pass bio-sound electrical signals, and a discriminator is connected to the transducer with the discriminator being programmed to pass a predetermined pattern of bio-soundwave electrical signals constituting a sonic profile of a selected aquatic animal. The resonance tube is adjustable to adjust the resonance frequency of the resonance chamber. In a preferred embodiment, the chamber is a hollow tube with the transducer at one end of the tube and, the opposite end being open so that when immersed in said body of water, water will rise therein and adjusting the resonance frequency by adjusting the depth of immersion of said opposite end. Sound absorbing foam can be applied to the exterior surface of the tube.

Abstract: One or more passive transducers for converting sounds, including bio-soundwaves from a living aquatic animal source traveling in a body of water, to electrical signals, is combined with an active sonar (echo sounding) to form an integrated marine acoustic system. Moreover, a common display can be used and coupled with a satellite (GPS) or loran position locator so that a fishing vessel carrying the apparatus can have its position displayed on an electronically reproduced chart or map of an area along with the fish location, including an indication of the direction of fish movement, and fish species.

Abstract: A cutting sound enhancement system (10) for transmitting an audible signal from the cutting head (101) of a piece of mine machinery (100) to an operator at a remote station (200), wherein, the operator using a headphone unit (14) can monitor the difference in sounds being made solely by the cutting head (101) to determine the location of the roof, floor, and walls of a coal seam (50).

Abstract: An underwater guidance system includes a transmitter located at a home base and generating a signal having a prescribed frequency. A diver wears a receiver on his wrist. The receiver includes a plurality of direction indicating elements and an out-of-range indicating element. The diver views the receiver to determine his position relative to the transmitter.

Abstract: A distance measuring method and apparatus in which first and second pseudo random signals which are the same in pattern but slightly different in period are generated to obtain a correlation output of the first and second pseudo random signals before transmission thereof as a reference correlation output, and the first pseudo random signal is directly transmitted toward a target or alternatively a carrier wave is modulated by the first pseudo random signal and transmitted toward the target. A correlation output of the signal reflected and received from the target and the second pseudo random signal is detected and the distance to the target is measured from the time interval between the reference correlation output and the received correlation output.

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: A system is disclosed for determining the location from which a sound blast having an identifiable audio signature originates. The system is particrly suited for determining the location of the muzzle blast from which a projectile, such as a bomb, is being launched by an enemy. The system comprises a plurality of elevated or airborne sensors whose position is accurately determined and which supply information to a land base station that performs the trigometric operations to ascertain the location of the enemy weapon.