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

Abstract: A method is disclosed in which the direction and range of sound generating targets (2) is determined solely by means of passive sensors (10, 11). In this connection it is proposed to employ a seismic sensor (10) in addition to the acoustic sensors (11) customarily required for a bearing angle determination. In this case, a line characteristic of the signal source of the target (2) is measured in the airborne sound spectrum as well as in the solid-borne sound spectrum and the radial target velocity (V.sub.z,r) is determined from the Doppler shift of these lines and the propagation velocity (C) of the corresponding waves and, under consideration of the bearing angle (.alpha.), the target range (r) is calculated therefrom.

Abstract: An underwater transducer system reproduces high-fidelity audio signals underwater, and detects and monitors low levels of sound activity, both adjacent to a body of water such as a swimming pool, and in the water. The system includes an underwater housing for a diaphragm that directly contacts the water, a coil assembly movable within the housing and rigidly connected to the center of the diaphragm by a tubular member of the coil assembly engaging a cylindrical boss portion of the diaphragm. The housing can be suspended by an elongated cord member from a wall coping, or mounted within a wall fixture structure. The system can have a source of illumination, a conduit from the source terminating in the housing on the coil axis proximate the diaphragm, and an optical element sealingly protrudes the diaphragm for transmitting light-amplified illumination into the water.

Abstract: Acoustically mapping (fingerprinting) the main channel, or `Q` routes, of a arbor, over relatively long time periods by using transducers anchored near the harbor or Q route floor. Sonar pulse returns are processed so that echoes from acoustic targets are constantly monitored and integrated over long periods of time. The integrated sonar data are used to establish a characteristic bottom-image map for the presence and location of permanent objects such as debris, underwater formations and the like. The long term, integrated record is obtained to establish a reliable acoustic fingerprint or reference mapping of the bottom. This acoustical record or map, which is quite stable over long periods of time, is used to compare newly detected acoustic variances from the established map. A combination of active and passive acoustic sensors that are installed at fixed positions submerged in the channel permit the determination of both range and bearing when an intruding object has been detected.

Abstract: A swimming pool alarm responsive to wave motion that will produce a signal when two waves exceeding a threshold level of amplitude are sensed within a preset duration of time. A transducer senses air or water pressure changes and produces electrical signals corresponding to the changes. A comparator system, connected to the transducer, receives the transducer signals and, if the signals exceed a preset threshold level, transmits a signal to the discriminator system. The discriminator times the signals received from the comparator and when two signals are received within a specified period of time, a third signal is generated. A warning device such as an alarm is connected to the discriminator and will be activated by the third signal.

Abstract: A system for detecting and classifying vehicles, moving in the vicinity of a seismic detector, includes a time threshold circuit and, complementary to this circuit, two parallel amplitude detector circuits. One detector circuit utilizes amplitude thresholding to distinguish the seismic vibrations characteristic of moving vehicles, from other seismic vibrations. The other detector circuit utilizes amplitude thresholding to distinguish the seismic vibrations characteristic of a particular kind of moving vehicle (e.g. a tracked vehicle), from other seismic vibrations. The results of these two amplitude detector circuits and of the time threshold circuit are utilized by an indicator circuit and an indication of detected vehicle kind (e.g. tracked or wheeled) provided. Indication may be relayed, to a remote observer, by radio transmission.

Abstract: A marine acoustic detector for use in identifying a characteristic airborne sound pressure field generated by a propeller-driven aircraft including a surface-buoyed resonator chamber tuned to the narrow frequency band of the airborne sound pressure field and having a dimensioned opening formed into a first endplate of the chambver for admitting the airborne sound pressure field. Mounted within the resonator chamber is a transducer circuit comprising a microphone and a pre-amplifier, the microphone functioning to detect the resonating sound pressure field within the chamber and to convert the resonating sound waves into an electrical signal while the pre-amplifier functions to amplify the electrical signal for transmission via a cable to an underwater or surface marine vehicle to undergo signal processing.

Abstract: A detection system for indicating the presence of motorized equipment in a esignated area having an acoustic sensor, a seismic sensor and an acoustic signal transmitter. The seismic sensor output, processed to discriminate against vibrations of short duration, is fed along with the acoustic sensor output, to an "ANDing" circuit which gates the acoustic transmitter. The acoustic sensor output is passed to the transmitter only during coincidence of seismic and acoustic detection.

Abstract: A detector system having a channel for comparing the peak amplitude of at least one of two electrical signals, produced at the output of two spaced geophones, against an amplitude threshold, to produce an indication of a moving object when this threshold is exceeded. To reduce the number of false indications, the system includes a parallel channel for measuring the phase difference between the two signals, and a processing circuit responsive to both channels, to ensure that indication is allowed only when the measured phase difference changes sense. The parallel channel includes four flip-flops each to measure the phase difference and the outputs of these flip-flops are added together, to produce a phase dependent signal for controlling the processing circuit. Further discrimination is provided by timing the phase transition, a time gate being used to inhibit indication when the phase transition does not occur within prescribed time limits.

Abstract: An active, relatively high gain, low power consuming band pass filter circuit centered at approximately 6 KHZ and having a pass band of 100-200 HZ. In a disclosed glass breakage sensor, the filter couples sensed ambient sounds of breaking glass to associated detection, driver and annunciator means. Signals of appropriate duration and frequencies indicative of breaking glass are thereby monitorable to define and induce an alarm condition within a security system.

Abstract: A system and method for enhancing detection of target signals in a passive detection system. The present invention enhances noise limited detection by combining energy from several frequencies, the fundamental and related harmonics. The present invention processes fundamental frequency signal f.sub.o and a plurality of harmonic frequency signals 2fhd o, 3f.sub.o . . . nf.sub.o that are embedded in background noise. In one embodiment these signals are summed and the summed signal is compared to a threshold to generate a target detection signal. In another embodiment, the plurality of harmonic frequency signals are processed to determine the background noise level and to determine which of the harmonic frequency signals may be harmonics of the fundamental frequency signal. The fundamental frequency signal and the harmonic signals that are determined to be harmonics of the fundamental frequency signal are summed to provide the summed signal.

Abstract: An analyzer recorder collects sonic boom information of supersonic aircraft and launch vehicles, for use to validate Environmental Impact Statements that contain supersonic aircraft activity. The device comprises a 16-bit microprocessor, a random access memory (RAM) storage, a data retrieval unit (DRU), and a microcomputer. It samples and captures in digital form any loud impulse noise from background noise. The unattended device can discern a sonic boom from the normal background noise and capture it in permanent solid RAM storage for later analysis. The RAM modules can then be transferred with the DRU and the information on the DRU transferred to the microcomputer. The microprocessor displays each recorded event, time of occurrence and summary information for all the stored data.

Abstract: An acoustic detector for detecting acoustic signals produced by vehicles. The detector comprises an acoustic sensor which senses an acoustic signal which is provided to a zero crossing detector. The zero crossing detector provides a digital signal representing the frequency of the incoming acoustic signal. The zero crossing detector's providing this digital signal to a first counter, the first counter's counting each zero crossing, and the first counter's reaching a predetermined count of zero crossings in a predetermined time for a predetermined number of times results in an acoustic alert provided to a secondary device which is put on alert of a vehicle in its vicinity. This secondary device may be a mine.

Abstract: A land vehicle sensing device includes a geophone for detecting vibratory gnals and a bandpass amplifier for limiting the electrical output of the geophone to those signals indicative of land vehicles. A real-time frequency analyzer provides a normalized power density spectrum signal which is threshold detected and averaged to provide an indication of land vehicle intrusion.

Abstract: A sensing apparatus capable of delivering a control signal in response to contact between an element of the apparatus and an external object should respond readily to a predetermined level of contact, and should be sensitive along all portions of the contact sensing surface. The instant invention provides a contact sensing apparatus including a conduit having a generally hollow tubular construction and being formed a resilient deformable material. A sonic generator is connected to one end of the conduit and a sonic detector is connected to the other end of the conduit. An electrical circuit is connected to the sonic generator and sonic detector, and is adapted to controllably produce a control signal in response to contact between the conduit and an external object.

Abstract: An apparatus and allied method for detecting the presence of submerged, possibly distressed swimmers in a body of water employs a plurality of pairs of transducers arranged on opposite sides of the body of water. Pulsed sequential excitation of the transducers is employed to monitor the body of water. A person disposed between a pair of transducers interrupts the transmission of ultrasonic waves. An alarm is triggered upon the interruption of the ultrasonic waves or after a delay to avoid false alarms, warning of the presence and location of a submerged, lingering swimmer even in the presence of other active swimmers in the body of water. The same apparatus can be employed as an intrusion detector to detect unauthorized entry of a person into an unguarded body of water.

Abstract: Apparatus 10 (FIG. 1(a)) for providing acoustic power spectra, all defined over a frequency band from signals received in a predetermined time interval, for individually identifiable directions comprises a pair of arrays 11, 11' of omnidirectional microphone elements 12. The time interval is divided into sampling periods and for each period the microphone signal sampled at 17, digitized at 21 and applied to array sample storage means 27 comprising corresponding shift register 28.sub.1. . . 28.sub.N for each microphone channel. Previously applied samples are clocked one stage with each new sample so each stage represents a delay of one sampling period. Register stages are connected to nodes 34 of a switching matrix 33, selected by ROM 36 to define the relative delays between samples for each beam direction and those samples read by the matrix are combined to form directed beam samples for that sampling period, stored at 40.

Abstract: In an acoustic ground vibration detector for the detection of infrasound ground vibrations, comprising at least one three-component geophone probe, the three individual geophones of said geophone probe are electrically connected in series and act upon an operation amplifier whose output signal activates a Reed relay. The activated Reed relay switches on a sound signal transmitter which produces an audible acoustic signal for the duration of the ground vibration signal. The acoustic ground vibration detector is intended in particular for locating buried persons. Moreover, it serves to protect important objects by registering infrasound ground vibrations produced by footfall sound.

Abstract: A sound reproducing system including a portable appliance reproducing sound from a recording and a transmission path transmitting reproduced sound to headphones worn by a user, and an apparatus for indicating to the user the occurrence of an abnormal event, causing a surge of ambient sound.

Abstract: An aircraft detection system which detects and tracks aircraft using: arrays of seismic and acoustic sensors, a set of junction circuits, a set of subarray circuits, several slave computers, and a master computer. Each junction circuit relays detected signals from several adjacent sensors to a subarray circuit and command signals to each of the sensors to adjust the gain of their output signals. Each subarray circuit receives and unites the outputs of several adjacent junction circuits into a subarray which has a particular geographical location in the array of sensors. Each slave computer forwards detected signals from single subarray circuit to the master computer, and relays command signals back to each individual sensor. Each subarray is able to track the seismic or acoustic signature of an aircraft as it travels across the regular distribution of sensors. Each subarray is thereby able to define an azimuth to the target aircraft.

Abstract: An apparatus and method for detecting insects detects insects by detecting ultrasonic signals which are generated by mechanical disturbances in material on which insects are feeding caused by the insects feeding on the material.

Abstract: A system for detecting and monitoring blast noise, the invention provides ncentrically arranged cylindrical windscreens having a pair of vertically spaced microphones mounted centrally therein, the windscreens acting to reduce interference from wind-generated pseudosound yet being acoustically transparent so as not to interfere with the reception of acoustical data incident on the microphones. The present system also includes a signal processing subsystem which receives the output of the respective microphones for analysis.

Abstract: An environmental interference detection device, consisting of IC.sub.4, D.sub.5, C.sub.13, R.sub.11, Q.sub.1 and a display unit, in which IC.sub.4 is used for signal phase inversion, D.sub.5 is used for filtering out the negative half wave of the signal, R.sub.11, C.sub.13 form a time delay circuit used to eliminate the sudden outbreak type of signal, and Q.sub.1 is used to drive the display unit. Users of an audio frequency detection device can use the indication of the display unit to adjust the sensitivity of the audio frequency detection device to a proper setting so as to efficiently utilize its monitoring function.

Abstract: In combination, intrusion detection apparatus giving a signal when a light vehicle approaches a geophone, and a heavy vehicle discriminator disabling the detection apparatus when the approaching vehicle is a heavy one.

Abstract: Geophone apparatus for receiving seismic signals due to an approaching vehicle, and giving an output when the signals are those characteristic of a heavy vehicle.

Abstract: The detection of low-flying aircraft is accomplished using both a microphone and geophone as sensors and a signal processing system for measuring the correlation between the seismic and acoustic signals. The signal processing system contains two amplification and band-limiting circuits, a delay circuit, an adaptive noise cancelling circuit, two signal smoothing circuits and a comparison circuit. The two amplification and bandlimiting circuits enhance a selected portion of the seismic and acoustic signals received by the sensors. The optional delay circuit is applied to the input acoustic signal, allowing the user the option of sensing or rejecting the detection of jet aircraft. The adaptive noise cancelling circuit generates an error signal by subtracting the signal components which are correlated between the seismic and acoustic signals from the input seismic signal. The first signal smoothing circuit improves the quality of the input seismic signal for comparison.

Abstract: A swimming pool alarm consists of a sensor suspended beneath the water surface of the pool, including an electrical resonator element and a captive element agitatable by the pool water adjacent the resonator element, and an alarm device external of the pool which responds to the amplitude of resonance of the resonator element exceeding a certain level.

Abstract: A passive method for obtaining target data from a sound source disposed in a nonsolid medium by means of a sound receiver remote from the sound source, by the steps of: providing, as the sound receiver, first and second sound-to-electrical signal transducers constituted and positioned to each respond to a respective one of two sound waves propagated from the sound source to the sound receiver at respectively different propagation speeds; and deriving, by means of an electrical signal processing system connected to receive output signals from the transducers, target data from the sound source by determining the frequencies of, or the difference in reception time between, the sound waves emitted by the source and to which the two transducers respond.

Abstract: A novel method for electronically determining the gross characteristics of he top layer of the earth's crust at a given location by using a passive seismic transducer as a sensing device for sensing background seismic noise in conjunction with as assembly of generally conventional miniature low power electronic components arranged in a system containing analog and logic circuits with a read-out meter calibrated to represent the detected background noise as seismic resonant frequency. The electronic determination of the crust character is in lieu of various conventional soil refractometry tests which are lengthy time-consuming procedures. The seismic resonant frequency has been found to be representative of the thickness and of the property or character of the crust at that particular geographical location.

Abstract: In combination: a geophone having a resonant frequency in the pressure wave band and a response that decreases with frequency below the resonant frequency; an amplifier connected to the geophone and having a gain which is substantially constant for frequencies above the resonant frequency, and which varies inversely with frequency for frequencies below the resonant frequency; a band-pass filter connected to the amplifier; a single channel rectifier connected to the band-pass filter; apparatus connected to the rectifier for obtaining short term and long term averages of the rectifier output; and apparatus including a comparator connectied to the last named apparatus for giving an output when the short term average exceeds the long term average by more than a predetermined amount.

Abstract: The apparatus comprises a geophone connected to a circuitry case containing battery, a voltage regulator, a solid state preamplifier and amplifier tuned to respond to seismic signals between 2 and 25 Hz. The amplified seismic signals are rectified and applied to a microammeter connected to efficiently respond to pulsations at the step frequency of walking or crawling personnel. The apparatus can be used to measure seismic noise and to determine soil conditions prior to the emplacement of an intrusion detection system.

Abstract: Alarm and intrusion type identification signals are derived from the output of a security system transducer by a signal processor. The signal processor conditions the transducer output signals to provide rectified and unrectified high pass and low pass frequency signals; develops signals representing either human or vehicle intrusions from the high pass frequency signals; develops signals representing intrusion events from the low pass frequency signals; and, logically classifies each intrusion event as either human or vehicle. Intrusion type identification signals are developed by counting zero crossings of the unrectified high pass frequency signal, measuring current energy of the rectified high pass frequency signal and logically comparing the two values.

Abstract: A method and apparatus are disclosed for detecting (ultrasonically or eletromagnetically) events of the presence and movement of a user within a defined user area, and a user operating zone within the user area, associated with a user device, such as an automatic teller bank machine, and for providing output signals indicative of those events. Transducer transceiver means is utilized with ranging circuit means and distance measuring circuit means. A computer means coupled to the distance measuring circuit means is also utilized to provide the output signals which may be used to control the operation of the user device and effect any corrective measures deemed desirable during its operation.

Abstract: The present invention provides a method and detection system for determining whether a person or other animate body is present in a vehicle by analyzing the power of the output signal from a geophone placed in contact with the vehicle structure. First an electrical signal is obtained which is a function of the vibrations emanating from the structure, and this signal is sampled on a contiguous basis over a plurality of time periods of equal duration. From these samples, a determination is then made as to whether a dense accumulation of power exists in the vicinity of the lowest power point of the sampled time periods and whether this lowest power point is above a predetermined minimum level. The system for accomplishing this method may include a seismic transducer used as a sensing device and a micro-computer for processing the output signals from the seismic transducer. The micro-computer will, on a continguous basis, sample about 22/3 seconds of data at a time.

Abstract: An electronic detection system for detecting intruders employs a transmisn line as a sensing element. In one embodiment the transmission line is a modified surface-wave transmission line, for example, a Goubau line, which is positioned about the perimeter of the area to be protected. An intruder in the field of the line causes an RF reflection back toward the source, which reflection may be detected by Doppler range-gating techniques. In other embodiments of the invention the transmission line is an insulated, twisted wire pair or a deformable transmission line. In some instances, the transmission line may be replaced with an active or passive pressure line.

Abstract: Seismic detection of a target is obtained with a geophone detecting earth vibrations caused by the actions of the target. The vibrations are wide band amplified and band-passed filtered with the pass bands being fed to the threshold detectors. The outputs of the threshold detectors are fed to a diode AND logic circuit, the output thereof indicating the presence of a target.

Abstract: An electronic detection system for detecting intruders employs a transmisn line as a sensing element. In one embodiment the transmission line is a modified surface-wave transmission line, for example, a Goubau line, which is positioned about the perimeter of the area to be protected. An intruder in the field of the line causes an RF reflection back toward the source, which reflection may be detected by Doppler range-gating techniques. In other embodiments of the invention, the transmission line is an insulated, twisted wire pair or a deformable transmission line. In some instances, the transmission line may be replaced with an active or passive pressure line.

Abstract: Apparatus for classifying the activity of an aircraft including the geophone proximate an airfield used by jet airplanes for generating a signal indicative of the existence of the jet aircraft. Amplifier means are provided for enhancing the signal. The signal is then passed through a low pass filter means for receiving the signal and passing only that portion having a frequency less than about 30 Hz. A high band pass filter also receives the signal and passes only that portion having a frequency ranging from about 90 Hz to about 120 Hz. Two demodulator means are provided which receive the low pass signal to provide a low pass envelope and receive the high band pass signal to produce a high band pass envelope. Threshold signal generating means are provided to receive the low pass envelope and the high band pass envelope, and generate a signal when either or both envelopes reach a predetermined threshold.

Abstract: Apparatus and method of processing in an ultrasonic alarm system to detect the doppler-shifted components which indicate the presence of an intruder. A master control applies to each of the transmitter transducers a signal which alternates between two frequencies at a modulation frequency. The output signal from the receiving transducer is synchronously detected and low pass filtered. The filtered signal is applied to electronics which respond to the presence of modulation frequency components in the filter output signal. A first embodiment utilizes a high-Q bandpass filter having a resonance frequency equal to the modulation frequency. In a second embodiment, the modulation frequency is used to effectively perform a correlation between the received signal and the modulation frequency.

Abstract: A dual signature perimeter detection system utilizing an elongated solenoid ype transducer having a ferromagnetic core as a line sensor is buried in the ground around an area to be protected against intrusion. One end of the transducer is impressed with constant frequency oscillator signals from a signal generator, while a resistance load impedance is connected across the other end of the transducer at the input side of an amplifier used to pass amplified signals selectively to the inputs of either a bandpass type filter or an A.M. detector, or to both simultaneously, then to their related alarms. The line sensor is sensitive to both magnetic and strain stimuli, but the system hereof, which utilizes dual alarm devices, not only provides for determining the type of stimulus creating the signals, but also improves the sensitivity and response uniformity of the transducer.

Abstract: The present invention relates to an intruder alarm system which compensates for background and other interfering noises. The system comprises dual amplifiers, one a main channel and the other a control channel wherein the control channel is responsive primarily to background and other interfering noises and develops a control signal which when applied as a control signal to modify the amplification characteristics of the main amplifier effectively removes the effect of the background and other interfering noises from the output of the main channel.

Abstract: A temperature measuring apparatus includes a transmitter for continuously transmitting an ultrasonic wave into a propagation medium the temperature of which is to be measured. Two receivers are located along an ultrasonic wave propagation path spaced from each other by a predetermined distance. A phase difference between the ultrasonic waves received by the two receivers is detected as a pulse width which varies depending on a propagation velocity of the wave and hence a temperature of the propagation medium. An obstacle detecting and alarming circuit is provided to detect the presence of an obstacle between the transmitter and the receivers by detecting the absence of the phase difference signal.

Abstract: A moving sound source identifying system wherein a correlation function signal between two sound signals derived respectively from two microphones arranged apart from each other on the ground for respectively receiving sounds which are simultaneously emitted by a sound source is used for identifying whether the sound source is moving or stationary and whether it is flying or moving on the ground, by means of discriminating the variation of respective times whereat maximum or minimum levels of the correlation function signal appear, which variation is caused in accordance with the angle of elevation of the sound source. Continuously obtained results of the identification are utilized for classifying sound sources, removing the noise disturbance and automatically pursuing the sound source.

Abstract: 1. A system for providing an improved triggering function for firing of a ne from the acoustic signature of a ship passing thereover or in the vicinity thereto comprising means for detecting the envelope of a portion of the audio signature spectrum of the ship, means for deriving a signal corresponding to the logarithm of said detected envelope signal, means responsive to said logarithm signal for providing a signal represntative of the first time derivative thereof, means for subsequently obtaining a signal simulating the second time derivative of said logarithmic signal, means for inverting the phase of said second time derivative signal, means for providing a multiplication of said first and second time derivative signals, and means responsive to said multiplied signals for actuation of a mine detonating circuit.

Abstract: In sound target detection equipment, at least three microphones are used in a broadside array manner to ascertain the presence of a selected sound source. The outputs of the three microphones all include the sought signal S and respectively contain noise components X, U and Y. These outputs are combined to provide X-U and X-Y. These two signals are then applied as separate inputs to a discriminator which applies the rules:(a) when the input signals are both of the same polarity, the discriminator selects the input closer to zero and presents it as the output;(b) when the input signals are of opposite polarity, the device presents zero as the output.The output from the discriminator is then subtracted from one of the original microphone outputs in a manner tending to cancel out the noise contents, and the resulting signal examined for the presence of the sought signal S. The invention is applicable also to non-aural signal detection equipment.

Abstract: A system for detecting the approach of a vehicle toward the line of sight an antenna comprises an alerter for receiving an acoustic noise signal from the vehicle and determining whether the signal is increasing or decreasing. The increase of a noise signal indicates the approach of a vehicle and is used to activate a power supply to supply power to a digital signal processor. The digital signal processor receives the acoustic signal and performs a comparison to determine whether the signal in fact is noise produced by a vehicle. If so, the digital signal processor activates a radar based primary sensor which more accurately detects the approach of the vehicle and determines the instant at which the vehicle passes an antanna of the sensor. When the vehicle passes the antenna, the digital processor receives data and produces an output signal that can be used to activate a counter to count the passage of vehicles, surveillance equipment or to fuse a mine if the vehicle is assumed to be hostile.