Abstract: A method for locating structure-borne sound events in pressure enclosures to be monitored in power plants, includes positioning sensors at various locations on a pressure enclosure. Signals are picked up with each of the sensors upon arrival of a sound wave generated by a structure-borne sound event and propagating along the pressure enclosure. The signals are stored in recording devices disposed downstream. A location of the structure-borne sound event is determined with a hyperbolic section method, from transit time differences resulting from different arrival times of the sound wave at two different sensors. Each range of possible speed values for the propagation of the generated sound wave is made a basis of one respective structure-borne sound event. The hyperbolic section method is performed separately for each speed value of the range for outputting a location indication with an error. The location with the least error is selected as the most likely location of the structure-borne sound event.

Abstract: A vibrating probe for detecting a threshold level of solids within a vessel consists of an ultrasonic acoustic transducer assembly having a resonant frequency, the assembly being supported within the vessel and including a coupling member to couple the transducer acoustically to the solids at the threshold level, a transmitter for generating repeated bursts of high-frequency electrical energy and applying them to the transducer, the bursts being of sufficient amplitude to render the assembly self cleaning of adherent solids, a circuit for measuring the amplitude of ringing of the transducer after cessation of each burst, and a circuit for comparing the amplitude of such ringing at a predetermined interval after a burst with predetermined threshold level. Both the predetermined interval and the threshold level may be selectable.

Abstract: The position of an object which is moved along a prescribed path, for example an elevator cage, is continuously and accurately monitored by coupling an acoustic signal generator carried by the object to an acoustic signal conductor which extends along the path, the acoustic signal conductor being characterized by the velocity of sound propagation therealong being uniform and constant. The position of the object is calculated by processing signals generated by transducers located at the opposite ends of the acoustic signal conductor, the signal processing determining the delay between receipt of a sound signal originating at the object at the opposite ends of the conductor.

Abstract: A method for selecting a set of four target bearings from a plurality of bearing measurements to optimize rapidity, accuracy and stability of a target track solution in a bearings-only target motion algorithm. Four bearings are selected to generate the deterministic solution by first selecting a candidate bearing set, then computing a set of "n" solutions from the candidate set and others adjacent thereto. Motion parameters are then computed, and any solution exhibiting parameters outside a user defined deviation from the mean is discarded. The mean target parameters of the remaining solutions may again be computed, and further culling out performed, until the desired distribution is achieved. An optimal solution is chosen as the solution from the remaining sample space that is closest to the mean in target range, course and speed.

Abstract: The bearing accuracy and long-range sonar target detection capability of a multi-cardioid directional receiving hydrophone array is improved by electronically producing mirror images of the cardioid directional patterns of each directional hydrophone in the array whereby the number of receiving channels are effectively doubled by this invention which in turn results in higher signal-to-noise ratios especially when receiving distant relatively weaker sonar signals. As a result, the accuracy of measurement of target range and bearing by the improved directional hydrophone array will be significantly increased.

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: The invention is directed to an improved acoustic sensor system for detering the direction of underwater sound signals relative to a user is disclosed. The sensor system includes first and second sensing means for sensing incoming acoustic energy and for providing first and second acoustic energy signals in response thereto; separation means for separating the first and second sensing means a distance S=E(C.sub.W /C.sub.A) where E is substantially equal to the separation distance between the users ears, C.sub.W is the speed of sound in water, and C.sub.A is the speed of sound in air; detector means, operatively connected with the first and second sensing means, for providing first and second output signals in response to the first and second acoustic energy signals; and audio means, operatively connected with the detector means, for providing an audio output to the user in response to the first and second output signals.

Abstract: A system for selective sound capture for hands-free telephony and multimedia workstations of the acoustic antenna type with an aerial formed by a member with a concave cylindrical surface. The system includes a plurality of electro-acoustic transducers which are distributed over and in the vicinity of the cylindrical surface. Circuits for partial summation of a plurality of analog sound signals make it possible to form elementary acoustic antennas and a summation circuit produces a resultant analog signal representative of the sound signal arising from a useful speaking area.

Abstract: The present invention comprises a method for filling in missing data intels in a quantized time-dependent data signal that is generated by, e.g., an underwater acoustic sensing device. In accordance with one embodiment of the invention, this quantized time-dependent data signal is analyzed to determine the number and location of any intervals of missing data, i.e., gaps in the time series data signal caused by noise in the sensing equipment or the local environment. The quantized time-dependent data signal is also modified by a low pass filter to remove any undesirable high frequency noise components within the signal. A plurality of mathematical models are then individually tested to derive an optimum regression curve for that model, relative to a selected portion of the signal data immediately preceding each previously identified data gap.

Abstract: A method and apparatus are provided for imaging an object using a transducer array for transmitting one or more beams that are steered and/or translated to transmit scan lines for multiple excitation events so as to scan a field of view of the object, for sensing received signals reflected from the object after each excitation event on one or more receive beams on receive scan lines, and for transducing those sensed received signals into corresponding electrical signals.

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 for minimizing measured quantities determined from sensors affected by measuring failures and detected by a plurality of redundant sensors connected to form a measuring system by detecting and isolating the sensors affected by failures. Sensor values measured by all the sensors are mapped by a linear transformation into a vector in the parity space (parity vector). The dimension of the parity space is determined by the redundance of the measuring system (i.e., the number of sensors and the dimension of the quantity to be measured).The subspaces at each failure level that contain the largest proportion of the measured parity vector are determined by projection of the measured parity vector onto all possible subspaces. The best sensor combination at each failure level can be determined by omitting the sensor combinations belonging to such subspaces.

Abstract: A short baseline navigation system employs the real-time estimation of the positions of multiple cooperative targets. Each target replies with a unique stepped frequency sequence signal that covers the usable frequency band. A processor operates on reply signals received by elements on the tracking platform and develops a coarse time-difference-of-arrival estimate using an algorithm derived herein. The processor also estimates the Doppler shift of received signals, and determines a time-window (or gating) that eliminates the portions of the received signals corrupted by multipath interference. The relative phase differences between the received signals are then used in conjunction with the coarse time-difference-of-arrival estimates for a precise direction-of-arrival estimation.

Abstract: The acoustic noise monitor determines acoustic sound levels radiated or stered to an exterior or interior fluid space of a structure such as an enclosed structure by measuring a condition, such as strain level, of the structure itself rather than by directly measuring the fluid itself. From the strain or other condition measured on the structure, the acoustic sound levels can be calculated with the Helmholtz integral. The sensors on the structure are preferably spaced so that non-radiating high wave-number motions of the structure are averaged out. The acoustic noise monitor can be used with submarines, jet aircraft, cars, or the like.

Abstract: An apparatus and method for accurately determining the relative locations of sensors in a passive sonar or like monitoring system utilizes two non-parallel (but not necessarily orthogonal) calibrator signals to calculate the relative positions of sensors in a sensor array. Iteration, using a deformed line array constraint, permits reliable solution of the sensor position equations, even when the relative angle between the calibrator signals is initially unknown.

Abstract: The present invention relates to a system and a method for determining the earing of an object located at a distance from a reference point. A plurality of sensors are mounted to a body to detect signals emanating from the object and to convert those signals into electrical signals. The electrical signals are then processed to determine the bearing of the object from the body. The system can include a float with the body suspended from said float immersed in a fluid medium. A method for processing the electrical signals and generating the bearing information is also described.

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 signal processor for obtaining frequency and bearing information of an ustical signal. Responsive to the acoustical signal, a multimode hydrophone generates a plurality of electrical signals which are combined to form a first omnidirectional signal and two spatially orthogonal directional signals. The directional signals are then combined to form a second omnidirectional signal. Additional circuitry is provided to analyze the two omnidirectional signals using the cross-spectral density function of the two omnidirectional signals to obtain said frequency and bearing information.

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 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 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: 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 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 method for characterizing ocean bottom properties in real-time by explong the multipath structure of reverberation to extract values for bottom loss and the bottom scattering coefficient. The bottom parameters are extracted from a measured reverberation energy envelope generated from the reverberation returns of one or more pings from a sonar system. The measured reverberation envelope is compared to a reference reverberation model to identify a period of time in which the measured reverberation energy envelope exhibits properties that allow the extraction of bottom parameters. The bottom parameters are then extracted by direct comparison of the measured reverberation to the reference reverberation model within the time period or by iteratively changing the value of bottom loss or bottom scatter coefficient and recalculating the reference reverberation for the identified time period until the reference reverberation matches the representative reverberation.

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: A system for facilitating the tracking of a target vehicle in connection h successively-received acoustic sensor signal data items. A fast Fourier transform operation is performed in connection with each successive acoustic sensor signal data item to generate a phase and amplitude beam map reflecting spectral signal energy in the received acoustic sensor signal data item. If the beam map for a acoustic sensor signal data item indicates that the item represents a signal having a signal-to-noise ratio above a first predetermined threshold value, a beam map generated for a previous acoustic sensor signal data item is used to generate a bounded beam map, a determination is made as to whether the bounded beam map represents a signal having a second predetermined signal-to-noise ratio. In response to a positive determination for the latter signal-to-noise determination, both the beam maps are used to generate tracking information for the target vehicle.

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: An ultrasonic distance meter cancels out the effects of temperature and humidity variations by including a measuring unit and a reference unit. In each of the units, a repetitive series of pulses is generated, each having a repetition rate directly related to the respective distance between an electroacoustic transmitter and an electroacoustic receiver. The pulse trains are provided to respective counters, and the ratio of the counter outputs is utilized to determine the distance being measured.

Abstract: A system for target detection and localization with an algorithm for performing target motion analysis (TMA) using data from a passive sonar array and which works directly with beam spectra to estimate the target track. The system determines when the coordinate trajectory of a hypothesized target aligns with the coordinate trajectory of an actual target and operates by forming long-term integrated spectral values from short-term values of frequency and angle coordinate values. The hypothesized target track that yields the maximum long-term integrated spectral value is used as the estimate of the true target track. A track generator is used to generate hypothesized target tracks for a search grid in the form of vectors that are clocked downward in a chain of latches. The latches are connected through computational elements, which are supplied with non-acoustic data, and RAMs to a summation pipeline, the RAMs being supplied with data from an array's sonar processor.

Abstract: A method and apparatus for processing a set of signals to identify narrow bandwidth features of the signals, and optionally to process the signals further to extract information about the identified narrow-band features. The invention processes a set of input signal frames (a multi-dimensional pixel array) to generate a narrow-band feature signal (also a multi-dimensional pixel array) from which narrow-band features of the input signal frames can be efficiently, automatically, and unambiguously identified. In a class of preferred embodiments, the input signal frames are the power spectra of a set of sequentially measured signals. Thus, the set of input signal frames is a "spectrogram," comprising rows and columns of pixels (with row indices representing time, and column indices representing frequency). Alternatively, the input signal frames represent a data array of another type, such as a correlogram or a sequence of images.

Abstract: An automatic detection apparatus and method applies the Short and Toomey algorithmic processing procedure to a frequency and beam direction windowed and time segmented set of Fast Fourier Transform (FFT) magnitude detected data, comprising time, frequency and beam direction data, to determine the presence or absence of narrowband lines indicative of target tracks. This is achieved by storing the time, frequency and beam direction data, and then processing this data using a predetermined three-dimensional maximum a posteriori procedure whereby individual target tracks associated with each beam direction are concurrently processed, and whereby transitions are made between adjacent beam directions in order to process target tracks having a maximum signal to noise ratio to provide for detection of a target. An output target track is generated by combining the high signal to noise ratio portions of the processed individual target tracks into a single output target track.

Abstract: A method for suppressing or removing coherent noise from seismic or borehole data is disclosed. The method requires horizontal alignment of the traces, comparison of the amplitude, phase and/or shape of neighboring traces, and subtraction of traces from neighboring traces only where the local correlation is high.

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: A curvilinear wideband, projected derivative-matched continuous aperture acoustic transducer includes a first curvilinear sensor having a predetermined spatial shading which is constrained to zero at its ends and has amplitude continuity between its ends; and a second curvilinear sensor area having a spatial shading which is the projected spatial derivative of the spatial shading of said first area and which has a discontinuous amplitude at its ends; the first and second spatially shaded areas being superimposed and coextensive along the sensing axis.

Abstract: An array of acoustic sensors is positioned near the object to be imaged so that an array of detection beams impinge upon the surface of the object. The ambient noise in the ocean which is generated by both natural and manmade phenomena is reflected off of the target object and collected by the acoustic sensors. Each beam corresponds to a single pixel of an image of the object. The amplitude and frequency differences between the signals derived from each beam permit contrast to be developed between the pixels so that an image is formed. A first embodiment utilizes a parabolic or spherical reflector to focus the noise reflected from the object onto one or more sensors. A two dimensional array of sensors is required to produce an image. A second embodiment uses a phased array of acoustic sensors to form an image, with the phased array of sensors being used to generate a large number of scanned beams, each beam corresponding to one pixel of the image.

Abstract: A wideband, derivative-matched, continuous aperture acoustic transducer includes a first sensor area having a predetermined spatial shading and a second sensor area having a spatial shading which is the spatial derivative of the spatial shading of the first area; the first and second spatial shaded areas are superimposed and co-extensive along the sensing axis.

Abstract: Sonars provided with an acoustically transparent antenna. In a sonar comprising deployable arms (2) provided with columns (4) distributed on a cylindrical surface, the invention provides for the doubling of said columns (7) situated at a small distance from the first columns and for the association of signals from hydrophones mounted in the columns so as to obtain for each pair of columns a cardioid characteristic simulating a baffled antenna. The invention makes possible the suppression of the rear lobe of an acoustically transparent antenna.

Abstract: A method and to a sensor for determining the distance of sound generating targets, preferably wheeled or track-laying vehicles, from acoustic signals which are subjected to a Fourier transformation. In order to determine the target distance easily and reliably, it is provided that the acoustic signals received by an acoustic sensor at two successive points in time from a target that is at a distance r.sub.1 and r.sub.2, respectively, from the acoustic sensor are employed, after the Fourier transformation, for an evaluation of the phase difference in the sound spectrum which yields the difference between the distances of the target from the sensor at the two points in time, from which difference the target distance is then calculated according to the spherical wave model.

Abstract: Apparatus and method for the electro-acoustical measurement of the angle ection of passing projectiles at air-tow-targets, wherein at least three acoustical sensors are equidistantly positioned on a fixed sensor ring which is supported by the tow-target, wherein the arrival times of the waves of the projectiles are electronically measured by means of the several sensors.

Abstract: A method and apparatus for processing a set of signals to identify narrow bandwidth features of the signals, and optionally to process the signals further to extract information about the identified narrow-band features. The invention processes a set of input signal frames (a two-dimensional pixel array) to generate a narrow-band feature signal (also a two-dimensional pixel array) from which narrow-band features of the input signal frames can be efficiently, automatically, and unambiguously identified. In a class of preferred embodiments, the input signal frames are the power spectra of a set of sequentially measured signals. Thus, the set of input signal frames is a "spectrogram," comprising rows and columns of pixels (with row indices representing time, and column indices representing frequency). Alternatively, the input signal frames represent a data array of another type, such as a correlogram or a sequence of images.

Abstract: A new method for measurement of the directional spectra of surface gravity (water) waves. Measurements are made at a single point by orthogonally mounted seismometers buried below the seabed surface and a pressure sensor resting on the seafloor or buried below the seabed. The maximum entropy principle is used to find the directional distribution function for the waves traveling through the sediments as measured by the seismometers. This function is combined with the frequency spectra of the ocean surface waves to form the directional spectra of the surface gravity waves. The method produced high directional resolution for instruments that were adequately coupled with the seabed. The method is also capable of detecting objects moving through water, such as surface ships and submarines.

Abstract: A wideband, derivative-matched, continuous aperture acoustic transducer includes a first sensor area having a predetermined spatial shading and a second sensor area having a spatial shading which is the spatial derivative of the spatial shading of the first area; the first and second spatial shaded areas are superimposed and co-extensive along the sensing axis.

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: Apparatus and method for transmitting and receiving hydroacoustic pulses used to determine the spatial separations between pairs of such apparatus. According to a preferred embodiment, the apparatus transmits hydroacoustic pulses having a selected shape and frequency at specific times and also determines the time of arrival of received hydroacoustic pulses having a known shape and carrier frequency. Included is a transducer for converting the hydroacoustic energy received from a body of water into electrical energy and for converting electric pulses into hydroacoustic pulses which are then coupled into the body of water. Electric pulses having a selected shape and carrier frequency are digitally synthesized in response to a count comparator.

Abstract: A system separates unknown signals which have been combined together through unknown linear filters and for which observations at multiple sensors are made. In a two channel circuit with two inputs and two sensors, the reconstructed source signals are assumed to be decorrelated such that the cross-correlation between the reconstructed source signals is near zero. The transfer functions which represent the crosstalk processes are estimated. The output signals are detected and the transfer functions are recursively solved. A reconstruction filter is used to recover the original input signals.

Abstract: A method for determining the angle of impact of an object on a thin-walled structure which determines the angle of impact through analysis of the acoustic waves which result when an object impacts a structure. Transducers are placed on and in the surface of the structure which sense the wave caused in the structure by impact. The waves are recorded and saved for analysis. For source motion normal to the surface, the antisymmetric mode has a large amplitude while that of the symmetric mode is very small. As the source angle 22 increases with respect to the surface normal, the symmetric mode amplitude increases while the antisymmetric mode amplitude decreases. Thus, the angle of impact is determined by measuring the relative amplitudes of these two lowest order modes.

Abstract: A method and apparatus for monitoring moving vehicular traffic, especially adapted for the detailed profiling and counting of airport usage by aircraft employing Doppler radar and sound generated by target aircraft. A primary parabolic reflector operated in the Cassegrainian mode with respect to Doppler radar radiation, employed in combination with a hyperbolic sub-reflector constructed so that it will reflect the radar radiation but remain transparent to sound waves is used to propagate and receive radar radiation, and to receive sound waves emanating from a target aircraft. Sound waves emanating from the target are received by the parabolic reflector and directed toward the parabolic reflector's primary focus where they strike a microphone placed at the primary focus of such reflector. The signal from the microphone and the information from the Doppler radar unit are processed by a central processing unit to provide a variety of information relating to the target aircraft.

Abstract: An integrated active/passive transducer system includes an active transducer for converting ultrasonic electric energy to pressure waves launched in a body of water and converting reflected ultrasonic pressure waves from a target in the body of water to a first electrical signal. A passive transducer coaxial with the active transducer, converting biosound pressure waves from a living organism in the body of water to second electrical signals. A first processing channel is connected to receive the first electrical signals and determine range to the target. A second processing channel is connected to receive the second eleectrical signals and provide a biosound signal. Logic system connected to receive the first electrical signal and said biosound signal, to validate that the target is a living organism and not an inanimate object only in the presence of biosound signals, and an indication is connected to the logic means for indicating that the target is a living organism.

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.