Abstract: A system for detecting the presence of intruder targets in an area under ar surveillance and in which the number of normal targets may vary, including the processing of gated time sample receiver signals through a first monitoring circuit having a counter and comparator means to develop output signals representing deviation of actual time sample count from a normal reference count, and through a second monitoring circuit including additional counter and count trigger means for developing an alarm signal responsive to continued deviation of actual count from reference count over several actual counts in a time sequence of counts such that normal variation of target number will not produce an alarm signal.

Abstract: The invention relates to a hydroacoustic sonar system in which received signals are processed without extensive filtering thereby to conserve higher fourier components of the received signals and so conserve useful information of targets. This is achieved by using a wideband detector module to effect demodulation of the received signals, and so eliminating the usual intermediate frequency stage. The module comprises a wideband input amplifier, a wideband full wave detector and an active low pass filter having a cut off frequency of at least 50 kHz.

Abstract: An electronic barrier utilizes a bifurcated beam of wave energy to establ a barrier area having a null between the forks thereof. Objects encroaching on said beam cause a portion thereof to be scattered in the foreward direction. Suitable receiver equipment located remote from the source of the bifurcated beam and responsive to the foreward scattered beam is connected to provide an indication of said encroachment.

Abstract: A channel adaptive active sonar is disclosed, wherein the sonar transmit waveform is adaptively selected in accordance with the measured sonar channel scattering function to reduce the response of the sonar to unwanted reverberation while preserving the response to signal returns. As a result, the sonar target detectability is improved over sonar systems which do not adapt to the variable properties of the ocean channel. The sonar is operable in two modes, the channel measurement mode and the normal active mode. In the channel measurement mode, probe signals are transmitted to test the channel response. From the sonar receive signals resulting from the transmitted probe signals, the channel scattering function is estimated. The transmit waveform for the sonar active mode is then designed to provide a waveform whose ambiguity function overlaps minimally with the estimated channel scattering function.

Abstract: The present invention relates to an apparatus for use in detecting the substance of an object contained within an enclosure. The apparatus is comprised of an acoustic transmitter for transmitting a pulse of acoustic energy at a first side of the enclosure. A first acoustic receiver is provided for receiving acoustic energy reflected from the object to produce a reflected acoustic energy signal. A second acoustic receiver is provided for receiving acoustic energy which has been transmitted or refracted through the object to produce a transmitted acoustic energy signal. A signal processor is connected to the transmitter and to said first and second receivers. The signal processor processes the transmitted pulse of acoustic energy, the reflected acoustic energy signal and the transmitted acoustic energy signal to produce an object signature indicative of the object. A comparator is provided for comparing the object signature with the signature of known objects to determine the substance of the object.

Abstract: A system is provided for the detection of an unsuitable water condition in which either large globules of solid material or bait fish suspended in the water beneath a vessel adjacent the hull of the vessel are detected and the associated depth sounding device is inhibited from providing a depth output. This eliminates the display or annunciation of erratic depth data, or the use of erratic data for closed or open loop control systems. In one embodiment, the unsuitable water condition is sensed through the detection of returns in a short water column adjacent the hull. In a further embodiment, returns from the water column coupled with receiver gain being open above a predetermined threshold provide the indication of the presence of the unsuitable water condition.

Abstract: In the field of the echography, the present invention is a system and method of preprocessing and transmitting information (such as echo waveform information) from a source (such as a transducer) to a destination (such as a rule-based computer system). The present invention reduces the absolute amount of information that is transmitted without reducing the amount of meaningful information that is conveyed. In this way, the present invention is effectively able to transmit more meaningful information than would be expected for conventional transmission systems. It also acts to reduce the amount of information processing that must be done at the destination.

Abstract: An electrical circuit to detect frequency domain information from ultrasonic signals that have been doppler shifted by motion of an object in the field of the ultrasonic beam. The circuit receives the doppler shifted signal, creates separate upper and lower sideband signals and compares the signals to a threshold level to produce digital transition pulses. The transmitter pulses are digitized to form pulses of uniform width and amplitude, whose frequency can be correlated to the object motion.

Abstract: A noise trap circuit particularly suitable for use in an electro-acoustic system, operates to suppress low level signals or noise while allowing a relatively large signal to pass unattenuated between input and output terminals of the circuit. Blocking elements between the input and output terminals establish a high impedance path to the noise but switch to a conductive state when the large signals are present at the input terminals. Shunt elements across the output terminals provide a low resistance path or "crowbar" when only the noise is present at the input terminals, but switch to a non-conductive state when the large signals are sensed at the circuit input.

Abstract: A method of simulating phase coherent signal reflections in media containing randomly distributed targets capable of scattering signals transmitted through the media, wherein the energy of signals directly scattered by the targets is significantly greater than the energy of signals multiply scattered by the targets. A reference signal having a wavelength which is small in comparison to the mean spacing between the targets is modulated and then transmitted through the target-containing medium. The targets produce scattered echoes of the signal, from which normalized in-phase and quadrature components are derived and separately, cumulatively summed, "n" times, until their variance becomes a linear function of 1/n.

Abstract: Target discrimination involves processing of sonar echoes in the time-dom and using features of the targets that the human auditory system uses (time separation and amplitude of echo highlights). Known targets are placed in the water and ensonified by multiple broadband transient signals. Echoes from each of the known targets have time-domain feature data extracted and stored to construct a library of known target features. Unknown targets echoes of transmitted multiple broadband transient signals are received and time-domain feature data is extracted from these. A comparison of the unknown target echo features with the known target echo features provides a discrimination of the unknown target echoes.

Abstract: System for seismic profiling of structures (2) beneath the sea bottom, comprising an acoustic transducer array (12) which synchronously and coherently generates an acoustic wave adapted to be reflected from said structures (2). When the reflected acoustic waves propagate towards the water surface (1), there is caused a perturbation of the electromagnetic reflection coefficient thereof. Receiver means for detection and characterization of the received acoustic field at the surface (1), comprises a radar system (10) illuminating the region concerned of the surface (1) and imposes thereat a number of interferograms each corresponding to the acoustic field from a scattering point given by the position thereof and the frequency of the field. By recording the degree of coincidence between the interferograms and the acoustic perturbation pattern on the water surface (1), the seismic properties of said structures (2) are surveyed.

Abstract: This invention uses an ultrasonic transmitter and receiver and a microprocessor to detect the presence of an object. In the reset mode the invention uses a plurality of echoes from each ultrasonic burst to create a reference table of the echo-burst-signature of the empty monitored environment. The invention then processes the reference table so that it only uses the most reliable data. In the detection mode the invention compares the echo-burst-signature of the present environment with the reference table, detecting an object if there is a consistent difference between the echo-burst-signature of the empty monitored environment recorded in the reference table and the echo-burst-signature of the present environment.

Abstract: System to measure the coefficients of reflection of submerged surfaces such as the seabed, by comparison of the intensities of acoustic impulses propagated between a source and a receptor, both of which are submerged, and that of the echoes of these impulses on the reflectors. For this purpose, there is provided a programmed calculator, an interface card to communicate with different units: an echo-sounder, a source triggering detector, a shot box to control the source and a recorder, a programmable attenuator, an acquisition card driven by the calculator and bearing an adjustable type filter and a circuit, also controlled by the calculator, for modifying the functioning parameters of the attenuation and of the filter, and fixing the starting parameters.

Abstract: A system of emission array with several pairs of emitting transducers to emit simultaneously and covering contiguous frequency sub-bands of a band B. The sub-bands have a width which is less than or at most equal to the width inducing an acceptable displacement of the directivity lobes of the emission pattern of a pair of arrays. The emitters of a single pair are spaced by a distance of L.sub.i and emit signal pulses at frequency f.sub.i and of duration .tau..sub.e 1/.DELTA.f, the products L.sub.i f.sub.i being equal for all the pairs of emitters.The emission patterns of the various pairs of emitters accordingly coincide precisely, and, as the emitters are supplied with signals emerging from the oscillators which are in phase at the center of the pulse of duration .tau..sub.e, the pulse resulting from the superposition of the emitted signals is compressed in time.

Abstract: A differential transformer is used as a feedback sensor for generating an error signal sensed at the face of an element of a sonar transducing array. This error signal is used to correct the excitation signal to the transducer to correct both phase and amplitude errors in the vibration of the radiating surface of the transducer. In this way, the transmitting beam pattern for the sonar array is improved. The differential transformer is capable of sensing the mechanical motion of the transducer radiating surface without being affected by a strong electric or magnetic field. By using a separate differential transformer sensor and processing circuit for each transducer in the array, electrical cross-talk between the individual elements of the array is eliminated.

Abstract: Signal processing circuitry is disclosed for processing the echo signals of echo sounders to extract the leading edge of bottom echo components of the echo signals and to provide a reading of the average area under successive leading edges. Second and later bottom echo processing is additionally disclosed. Processing is achieved with a sample and hold circuit comprising an integrator (34), a first switch (33) for switching the required echo signal portion to the integrator, storage means (C2) for storing integrated values to be displayed, and a second switch (35) for selectively coupling values from the integrator to the storage means.

Abstract: Obstruction detector apparatus operatively coupled to an automatic electric door operator compares the time span of transmission and receipt of reflected echoes of ultrasonic energy within a door passageway obstruction zone with predetermined time spans in order to prevent door closure under conditions indicating passageway obstruction or system malfunction. Signal generators provide timing signals respectively representative of the anticipated time span of reflected echoes from locations in front of, and beyond, the door jamb opposite the ultrasonic transmitter and receiver transducers for comparison by a relay controller with the time of generation of a signal representing a reflected echo at the transducer receiver, the relay controller appropriately actuating a door operator relay in response to such comparison.

Abstract: An ultrasonic ranging system includes transformer means with a transformer which is selectively energized to produce a transducer drive signal. An ultrasonic transducer transmits an ultrasonic pulse in response to the drive signal and develops an echo signal upon receipt of an echo pulse derived from the ultrasonic pulse; a shunt switch is connected across a winding of the transformer and is selectively closed to quickly damp the ringing following the transmission of an ultrasonic pulse to a level substantially below the level of the echo signal to permit close ranging.

Abstract: A cylindrical member for preventing a roundabout of the supersonic wave is arranged around the transmitting and receiving opening of one of the sender or receiver of a supersonic wave device for a vehicle which is installed on the vehicle. Thereby the phenomenon of the roundabout of the supersonic wave is reduced and at the same time the duration time of phenomenon of the roundabout of the supersonic wave is decreased and the object of the short distance can be sensed.

Abstract: In a color sonar system especially suitable for displaying fish echo signals, high and low frequency echo image signals are displayed utilizing colors corresponding to the echo signal strength, when the signal strength differences between the simultaneously received high and low frequency echo image signals are within a preset level range, when the differences between the high and low frequency echo image signals are outside the preset level range, the selected high frequency or low frequency echo image signals are displayed utilizing colors indicative of the differences in signal strength between the corresponding high frequency and low frequency echo signals.

Abstract: A sonar or radar permits primary distributed scatterers that are close to the sonar or radar relative to the array dimension to be rapidly and accurately located and pertinent characteristics to be estimated, such as Doppler and complex scattering strength. The region viewed is partitioned in annuli instead of in angular pie shaped slices as is normally the case for conventional sonar. This avoids the difficulty with conventional sonar or radar of distinguishing whether a scatterer is in a side lobe or the main beam an dis preferable to conventional sonars or radars in the important case of approaching multiple scatterers, e.g. robotic vehicle sensors or torpedo terminal homing on a target, because near regions may be examined in all directions prior to further regions. Computational speed is achieved by utilizing precomputation and leaving only part of the computation to be performed in real time.

Abstract: A circuit arrangement for separating high-frequency pulses produced successively in time at a piezoelectric transducer of an acoustic reflection lens arrangement. According to the invention, the transducer is preceded by a three-way pin switch, the common end of the wiper of which is connected to the acoustic lens, the other end of the wiper being alternately connected in a first position to the output of a transducer oscillator, in a second position to a 50-Ohm resistor, or in a third position to a measurement circuit.

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

Abstract: A method for measuring the running time of a signal transmitted by a transmitter and received by a receiver is devised, where the signal is transmitted and received by the same transducer. For transmitting the transmitter is driven by an electrical pulse train, and in receiving the received signal is converted back into an electrical signal. In receiving triggering is done on the trailing edge of the envelope of the received signal. At the transmitting side the transducer after its incitement is driven by a pulse train being in phase opposition to the original inciting signal and having a larger amplitude than the original inciting signal which results in a higher steepness of the envelope. At the receiving side the maximum amplitude is measured, and the triggering point of time is determined when the actually measured value of the envelope falls below a certain percentage value of the maximum value.

Abstract: A circuit automatically determines the nature of the seabed over which a vessel is passing, indicating via an audible or other warning signal when a fishing vessel is above a type of seabed which might damage the fishing net. The circuit is responsive to an echosounder signal and raises an alarm when a amplitude of the second bottom echo component in the echosounder signal exceeds a selected threshold level. Preferably the analog echosounder signal is subject to threshold discrimination to provide a pulse-form signal which is then processed by a digital logic circuit to isolate the second bottom echo component.

Abstract: The acoustic characteristics, particularly the attenuation coefficient, internally of a object undergoing examination are measured on the basis of ultrasonic echo pulse, and diminishing the influence of the sound field. Standard media having attenuation coefficients that differ from one another are measured in advance by a predetermined method to find the attenuation rates and attenuation coefficients thereof. The attenuation coefficient of the object is taken to be the attenuation coefficient of one of the standard media that minimizes a difference between the attenuation rate of each standard media and the attenuation rate of the object, which is measured based on an ultrasonic echo signal from within the object.

Abstract: Method and apparatus for identifying a number of people in a monitored area wherein a first reflected ultrasonic wave map of the monitored area is collected that includes background objects. A second reflected ultrasonic wave map of the monitored area is collected when people may be present in the monitored area. The first collected background defining map is subtracted from the second collected map to obtain a resulting map. The resulting map is processed to identify clusters having a minimum intensity. A cluster size of the thus identified clusters is utilized to identify clusters corresponding to people. The ultrasonic detecting method and apparatus is utilized with a wave signal receiver for identifying an audience composition of the receiver and determining the viewing habits of the public.

Abstract: An acoustic transducer is connected to an electronically controllable time-dependent conductance so that energy may be rapidly applied to and extracted from the transducer and associated circuitry.

Abstract: A single transducer ultrasonic target detector and detection method are disclosed which provide for detection down to substantially zero distance from the detector housing envelope with an electroacoustic transducer subject to unavoidable ringing following emission of a burst of acoustic energy. The housing is configured with a retroreflecting surface proximate the transducer so that acoustic energy reflected from the target is repeatedly reflected back toward the target until the ringing has subsided sufficiently to permit reception of the reflected acoustic energy by the transducer.

Abstract: A system for sorting parts wherein a part to be sorted is irradiated with wave energy of a single frequency (or very narrow band of frequencies) which interacts with the part. Wave energy emanating from the part is sensed at many spatially separated places to generate an electric signal representative of a characteristic of the amplitude and phase of the detected wave energy at each place. The electric signal so generated is compared with a pre-established signal and any differences therebetween are determined to establish whether the part is within acceptable limits in terms of geometric characteristics, e.g., size, material characteristics and orientation. The part is then acted upon on the basis of the comparison.

Abstract: An improved ultrasonic transducer in which signals from portions of the transducer located a distance apart from each other are compensated for the cancellation affects due to a reflected energy striking one part before the other by use of switching circuits which pass either in-phase or out-of-phase components from the portions of the transducer to a summing circuit in such a manner that the summed output is improved.

Abstract: An array with high resolving power and low secondary lobe levels, comprising a receiving array formed of transducers along its length L.sub.R, two of these transducers, separated by a distance L.sub.E, also forming the transmitters. The change from transmission to reception and back is effectuated by switches. Signals received by transducers are weighted by resistors before being delivered to beam forming circuits, containing multi-terminal phase shifters and a wiring matrix and adders. The weighting function and ratio L.sub.E /L.sub.R are chosen to ensure that the overall transmission-reception system diagram has high resolving power and low secondary lobe levels.

Abstract: A solid state transmit/receive switching circuit is provided by a system which, in accordance with the invention, comprises a solid state relay which, when energized, causes an optically controlled resistor connected to an input terminal of a preamplifier of the receiver to change its resistance and hence the sensitivity of the preamplifier according to the transmitter transmission state.

Abstract: Devices and methods are disclosed for remote measurment of temperature (and velocity) profiles in a fluid medium (i.e., the atmosphere and/or oceans). Each device, herein called an echometer, and method are capable of providing remote measurements of temperature through the use of propagated waves (i.e., acoustic or electromagnetic waves) and interferometric principles. By use of Doppler processing, simultaneous measurement can be made of three-dimensional velocities at the same points in space to enable remote measurement of heat fluxes in the atmosphere or ocean.

Abstract: An ultrasonic wave transmitter and receiver adapted to be mounted on the rear portion of a vehicle to detect the distance between the rear end of the vehicle and any obstruction located at the rear side of the vehicle. The ultrasonic wave transmitter and receiver includes an ultrasonic transducer attached to a lower part of the vehicle at a portion spaced from the rear end of the vehicle in the forward direction of the vehicle by a predetermined distance, a horn opening rearwardly from the vehicle and a wave guide tube through which the horn and the ultrasonic transducer are coupled to each other. The distance between the ultrasonic transducer and the rear end of the vehicle is selected to correspond to a time length which is long enough to sufficiently attenuate the residual oscillation of the ultrasonic transducer.

Abstract: A sonar system for positive identification of certain resonant body targets such as mines. Two acoustic signals of different frequencies are transmitted toward the target and the acoustic returns are separated into the component frequencies, detected, and thereafter subtracted from one another. A signal, above a threshold value, resulting from the subtraction is indicative of a resonant body target and the indication is displayed and/or recorded.

Abstract: A sonar fish counter, primarily for counting salmon migrating in streams and for providing a separate count of king salmon, includes a narrow beamwidth side-scanning sonar transducer directed to insonify a volume of water in the stream directly above a mechanical beam which serves as an artificial bottom. The transducer transmits pulses of short duration such as 100 microseconds at regular intervals. After a delay following a transmitted pulse, a receiver is enabled to receive echo signals from any fish crossing the artificial bottom. During the period the receiver is enabled, a ring counter separates the return echoes on the basis of the return time from respective sectors of the bottom structure, and these returns are separately counted for each sector so that the counts may be displayed or printed separately.

Abstract: A method and apparatus for locating and mapping a pool of a pollutant (12) in a body of water (11) comprising the steps of scanning the bottom of said body of water with ultrasonic energy using a transducer (10) periodically pulsed to project pulse envelopes of acoustic energy downwardly to the bottom (14) of the body of water and receiving echo returns from the bottom preceded by echo returns from a reflective interface (13) with a pool of pollutant, if present. The presence of an echo return from an interface (13) as a precursor to an echo return from the bottom indicates the presence of the pool of pollutant at the navigational position of the transducer as the process of scanning continues. Locating and marking the perimeter of the pool permits rapid clean up operations to be directed.

Abstract: A unique method for detecting and sampling flying insect populations is disclosed. An agricultural area is baited with a specific sex pheromone of a specific flying insect. When the flying insect is lured into range of the bait, a low-frequency sound is transmitted into contact with the insect. The sound is received in a counting means and the detection of the insect stored. Accumulated detections over a period of time form a population sampling of the insect studied.

Abstract: In a receiver for pulsed ultrasonic beams, it is sometimes desirable to translate the received signal to a lower carrier frequency by a heterodyne process. It is also often desirable to vary the receiving channels' gain during the period when signals are being received from a single transmitted pulse, to compensate for the attenuation of later-arriving signals from a greater distance. To get both the heterodyne and the time-gain control functions in a prior-art receiver of N channels requires 2 mixers in each channel, or 2N mixers. According to the invention, the heterodyne and the time-gain control signals are combined in one master mixer and fed to all the channel mixers. The only N+1 mixers are required.

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

Abstract: A circuit for exciting an ultrasonic transducer element comprises a diode switch exhibiting a long reverse recovery time duration connected between an input and an output terminal. A transducer exciting signal varying in both positive and negative directions and applied to the input terminal is conducted to the output terminal through the diode switch.

Abstract: An ultrasonic signal transducer is characterized in that the piezoelectrically active element has a first unitary electrode over the entire surface of one face and a matrix of a plurality of individual electrodes on the opposite face. In the receive mode, such an arrangement effectively constitutes a plurality of individual transducers arranged in the matrix array while maintaining the efficacy of a unitary structure. The signals from the individual electrodes are individually amplified, full-wave rectified, and combined additively to produce a composite signal which eliminates the phase cancellation of the ultrasonic pulses distributed over the face of the transducer assembly.

Abstract: In a method and apparatus for surveying for nodular targets of a grain size of 1 to 15 cm present on the sea floor, pulse waves in each of three frequency ranges of 3 to 4, 10 to 14 and 25 to 50 KHz are radiated onto the sea floor from a ship navigating on the sea. The reflected sound waves of the three frequency pulse waves are received and the reflexibilities of the respective sound waves are measured from the reflected sound pressures and the reflexibilities are composed. The population of the nodular targets is determined from the composed reflexibility and, as required, the grain size of the nodular targets can be determined from at least one of the ratio of the reflexibility of the sound waves of the frequency range of 3 to 4 KHz to the composed reflexibility and the ratio of the reflexibility of the sound waves of the frequency range of 3 to 4 KHz to the reflexibility of the sound waves of range of 25 to 50 KHz.

Abstract: A fish detector capable of detecting species of fish. Two ultrasonic sounds at different frequencies and echoes are detected by receivers tuned to said different frequencies, respectively. The output signals from the receivers are converted into binary-coded signals and one of the binary-coded signal is divided by the other binary-coded signal. The ratio or quotient thus obtained is compared with a plurality of reference signals at different levels or strengths so as to detect whether or not the ratio or quotient is higher than the highest level or strength reference signal, lower than the lowest level or strength reference signal or between two reference signals at adjacent levels or strengths and subsequently to display in color depending upon a level of the ratio or quotient thus detected.

Abstract: A digital homodyne processing system is disclosed and includes a hydrophone, a preamplifier for amplifying the hydrophone output signal, a heterodyne circuit and a low-pass filter for filtering the amplified hydrophone output, and a digital-to-analog converter. The output of the digital-to-analog converter is compared against sine and cosine references and is integrated as a function of the sine and cosine references. The integration results are processed for detection of a coded waveform.

Abstract: A system for the automatic measurement of the level, of material in a container and especially of liquid flowing through a channel is described. An echolocation system operates to detect returns of reflected sonic signals from the surface of the liquid in the channel during successive transmission cycles. A source of pulses is provided having a frequency which provides a certain number of pulses corresponding to the travel time of the sonic signals over a distance equal to a maximum predetermined level or head of the liquid in the channel. The time interval between signal transmission and reception is excess of twice the time for travel of the signals between the transmitter and the maximum level of liquid is a measurement of the liquid level in the channel.

Abstract: The invention relates to a simulator for providing waveforms of the type produced at a receiver from a sonobuoy transmission. The simulator signal includes a component representing reverberation under different sea state conditions and a component representing echo pulses received from a target having relative motion with respect to the sonobuoy. Selected initial range and target speed values can be set in the simulator so that the signal includes a sequence of echo pulses having the varying delay and doppler shift which would occur from a target starting at the selected range and moving at the selected speed.

Abstract: A high resolving power arrangement of transmitting and receiving transducer for arrays the detection of targets in a wave detection system such as sonar. The arrangement includes a transmitting array including two transducers (T.sub.1) and (T.sub.n) transmitting in synchronism or alternatively in phase opposition and a receiving array including transducers T.sub.1, T.sub.2 . . . T.sub.n associated respectively with multiple connector phase shifters (D.sub.1), (D.sub.2) . . . (D.sub.n).