Abstract: A radar assembly and a method for operating the radar assembly is disclosed, where a first frequency comb generator is arranged in the transmitting unit between the first oscillator and the transmitting antenna and a second frequency comb generator is arranged in the receiving unit between the second oscillator and the first mixer. On the transmitter side a first frequency comb generator is controlled with the first oscillator frequency in order to generate a primary signal containing a plurality of frequency components, on the receiver side a second frequency comb generator is controlled with a second oscillator frequency in order to generate an output signal containing a plurality of frequency components, the output signal generated in such a way is mixed with a third oscillator frequency, and the intermediate frequency is generated by mixing the received reflected signal with the mixed signal.

Abstract: Marine seismic surveys, including ocean bottom surveys, utilizing marine vibrator arrays that are capable of being driven in anti-phase to produce a directional source gradient. Marine seismic surveys may include activating the vibrator array to emit a plurality of radiation patterns with at least a first radiation pattern that has a first notch at a take-off angle that is not dose to vertical. Some marine seismic surveys included emitting directive wavefields from two or more simultaneous seismic source arrays, where the two or more seismic source arrays have a phase that changes from shot-to-shot to allow simultaneous source separation of the directive wavefields.

Abstract: A system, article, and method of acoustic angle of arrival detection uses both same-time and delayed-time audio signal value comparisons in a time domain that are input to a classifier neural network.

Abstract: Techniques for noise suppression systems coupled to one or more microphone arrays are described, including a housing, a first microphone, a second microphone, and a third microphone, where the third microphone functions as a common rear vent for the first and the second microphones.

Abstract: The ultrasonic homing assembly includes a base unit that may be coupled to a boat anchor. A base processor is coupled to the base unit. A transmitter is coupled to the base unit. The transmitter is operationally coupled to the processor. The transmitter transmits a location signal. A remote unit may be worn by a diver. A remote processor is coupled to the remote unit. A receiver is coupled to the remote unit. The receiver is operationally coupled to the remote processor. The receiver receives the location signal from the transmitter. A display is coupled to the remote unit. The display is operationally coupled to the processor. The display directs the diver toward the base unit. The diver swims toward the boat anchor.

Abstract: Methods and systems are described for controlling an automation and security system. According to at least one embodiment, an apparatus for voice control of an automation and security system includes a processor, a memory in electronic communication with the processor, and instructions stored in the memory. The instructions are executable by a processor to detect a trigger word spoken by a user at a location remote from a control panel of the automation and security system, detect a command spoken by the user at the remote location which follows the trigger word, deliver at least one audio response to the user at the remote location in response to the command, and perform an action in response to the command.

Abstract: An acoustical module including a receiver unit for generating audio sound, microphone units for receiving acoustical pressure signals, and acoustical pressure pick-up points. Each of the acoustical pressure pick-up points is acoustically connected to a microphone unit. The module further includes an acoustical filter for attenuating acoustical pressure signals from a first acoustical pressure pick-up point relative to a second acoustical pressure pick-up point. The invention further relates to a hearing device comprising an acoustical module.

Abstract: A directional transducer array system comprising a plurality of transducers with mathematical sequence spacing mounted on an array tile or host device. In an embodiment, the invention allows the construction of a receiving or transmitting, tiled (modular) directional audio array while simultaneously retaining desirable directional characteristics, improving gain, and limiting negative impacts on side lobe attenuation as the array is scaled (i.e. identical or similar tiles are added to or subtracted from the array); and allows the construction of a receiving or transmitting directional audio array that is light weight and robust enough to be used in body-worn, body-carried, vehicular, and fixed installations.

Abstract: A vehicle direction identification device includes: a frequency analysis unit which analyzes amplitude or phase of surrounding sound in each analysis section; a sound source direction identification unit which identifies a sound source direction included in the surrounding sound for each analysis section; a vehicle identification information storage unit which stores first vehicle identification information including a first threshold value; a first vehicle identification unit which calculates a rate of occurrence of each sound source direction and identifies the sound source direction whose rate of occurrence is equal to or exceeds the first threshold value; a second vehicle identification information calculation unit which calculates second vehicle identification information including a second threshold value smaller than the first threshold value; and a second vehicle identification unit which identifies the sound source direction whose rate of occurrence is equal to or exceeds the second threshold value.

Abstract: An object probing device includes: a sound source which projects a sound pulse within a propagation environment; a transducer array disposed in a region for receiving the forward scattered wave scattered forward from the object existing in the propagation environment; an addition processing unit which extracts only a signal of the forward scattered wave by applying vector addition processing on a reference signal in a reference sound field received by the transducer array when the object does not exist in the propagation environment and a mixed signal in a probe sound field received when the object exists; a time reversal processing unit which generates a time-reversed sound pulse by applying time reversal processing on the extracted forward scattered wave; and a phase conjugation determination unit which checks whether or not a phase conjugacy is established in the propagation environment by employing a passive phase conjugation to the time-reversed sound pulse.

Abstract: Movements of objects within a space are adaptively detected by emitting ultrasound waves into the space and detecting reflections of the ultrasound waves, determining locations of objects within the space based on the ultrasound reflections, and determining real-time movements of the objects based on, in certain embodiments, (i) amplitude differences between amplitudes of echoes in a current wave cycle and an average amplitude over a plurality of wave cycles and (ii) elapsed times of the ultrasound reflections associated with the amplitude differences.

Abstract: The target searching device includes: a sound source which transmits a sound wave into a propagation space; a transducer array placed in an area to receive a forward scattering wave which scatters forward from the target within the propagation space; a subtraction processing device which subtracts a traveling wave directly traveling towards the transducer array from a mixed wave of the forward scattering wave and the traveling wave so as to separate the forward scattering wave; a passive-phase conjugate processing device which performs passive-phase conjugate processing on the forward scattering wave separated by the subtraction processing device so as to generate a passive-phase conjugated signal of the forward scattering wave; an autocorrelation processing device which performs autocorrelation processing on the traveling wave to generate an autocorrelation processed signal of the traveling wave; and a correlation device which judges a similarity between the autocorrelation processed signal and the passive-p

Abstract: Provided is a neuromorphic signal processing device for locating a sound source using a plurality of neuron circuits, the neuromorphic signal processing device including a detector configured to output a detected spiking signal using a detection neuron circuit corresponding to a predetermined time difference, in response to a first signal and a second signal containing an identical input spiking signal with respect to the predetermined time difference, for each of a plurality of predetermined frequency bands, a multiplexor configured to output a multiplexed spiking signal corresponding to the predetermined time difference based on a plurality of the detected spiking signals output from a plurality of neuron circuits corresponding to the plurality of frequency bands, and an integrator configured to output an integrated spiking signal corresponding to the predetermined time difference, based on a plurality of the multiplexed spiking signals corresponding to a plurality of predetermined time differences.

Abstract: Methods and apparatus of managing a communication system, wherein a decision regarding a level of activity at a first end is made based at least in part on the level of activity at the second end. In one embodiment, the energy level of a first-end audio signal is measured. The first end is declared voice-active if the first-end energy level is greater than or equal to a first threshold value. The first end is declared voice-inactive if the first-end energy level is less than the first threshold value. To determine the value of the first threshold value, the energy level of a second-end audio signal is measured. If the second-end energy level is greater than or equal to a second threshold value, the second end is declared voice-active, in which case the first threshold is maintained at a relatively high level. If the second-end energy level is less than the second threshold value, the second end is declared voice-inactive, in which case the first threshold is maintained at a relatively lower level.

Abstract: An underwater detection device includes a transceiver module for transmitting underwater an ultrasonic pulse signal that is frequency-modulated and receiving an echo signal corresponding to the transmitted signal, a pulse compression module for pulse-compressing the signal received by the transceiver module and outputting a signal pulse-compressed, a suppression range determining module for determining a suppression range where a range side lobe suppression process is performed for the pulse-compressed signal, an echo determining module for determining whether the data of the pulse-compressed signal at each depth corresponding to a range side lobe, a suppression value determining module for determining a suppression value for the data of the pulse-compressed signal at each depth, a suppression conducting module for performing a calculation to suppress the range side lobe based on the suppression value for the data determined to be data of the pulse-compressed signal corresponding to the range side lobe by the

Abstract: A method comprising determining at least one first parameter, wherein the first parameter is dependent on a difference between at least two audio signals; determining at least one second parameter, wherein the second parameter is dependent on at least one directional component of the at least two signals; and generating at least one ambience coefficient value dependent on the at least one first parameter and the at least one second parameter.

Abstract: An acoustic treatment apparatus obtains a first output signal by performing filtering for forming a directivity in a first direction for received sound signals of sound receivers, obtains a second output signal by performing filtering for forming a directivity in a second direction different from the first direction for received sound signals of sound receivers, obtains a strength ratio between a strength of the first output signal and a strength of the second output signal, and estimates a sound source direction on the basis of the strength ratio.

Abstract: Localization of remote devices by: the emission of pulses from acoustic transmitters, whose wavefronts propagate in the space region occupied by the remote devices and finally reach them; the emission of radiofrequency pulses from each remote device at the time of detection of the wavefront by an on-board microphone; the acquisition, by a radio base, of the radiofrequency signals propagating from the remote devices, to evaluate the arrival time delays proportional to the distance between the i-th acoustic source and the j-th remote device; the formation of a reception vector for each emission by the i-th source, this vector having a maximum length M equal to the number of remote devices and consisting of the sequence of distances obtained as the product of the reception times and the estimated sound velocity. These steps are repeated for all acoustic sources, to form N+1 reception vectors, to calculate the position of the device by solving derived matrix equations.

Abstract: An underwater detection device includes a transceiver module for transmitting underwater an ultrasonic pulse signal that is frequency-modulated and receiving an echo signal corresponding to the transmitted signal, a pulse compression module for pulse-compressing the signal received by the transceiver module and outputting a signal pulse-compressed, a suppression range determining module for determining a suppression range where a range side lobe suppression process is performed for the pulse-compressed signal, an echo determining module for determining whether the data of the pulse-compressed signal at each depth corresponding to a range side lobe, a suppression value determining module for determining a suppression value for the data of the pulse-compressed signal at each depth, a suppression conducting module for performing a calculation to suppress the range side lobe based on the suppression value for the data determined to be data of the pulse-compressed signal corresponding to the range side lobe by the

Abstract: Noise discrimination in signals from a plurality of sensors is conducted by enhancing the phase difference in the signals such that off-axis pick-up is suppressed while on-axis pick-up is enhanced. Alternatively, attenuation/expansion are applied to the signals in a phase difference dependent manner, consistent with suppression of off-axis pick-up and on-axis enhancement. Nulls between sensitivity lobes are widened, effectively narrowing the sensitivity lobes and improving directionality and noise discrimination.

Abstract: Systems and methods for detection and analysis of amplitude modulation of underwater sound employ a product of a time delayed first electrical signal with a second electrical signal to generate a summed-product signal. The time delayed first electrical signal and the second electrical signal have an amplitude modulation indicative of characteristics of a vessel propeller. The summed-product signal is analyzed to detect a vessel and to determine the characteristics of the vessel propeller. In some arrangements a plurality of summed-product signals are analyzed to also determine a depth of the detected vessel.

Abstract: Systems and methods for detection and analysis of amplitude modulation of underwater sound employ a product of a time delayed first electrical signal with a second electrical signal to generate a summed-product signal. The time delayed first electrical signal and the second electrical signal have an amplitude modulation indicative of characteristics of a vessel propeller. The summed-product signal is analyzed to detect a vessel and to determine the characteristics of the vessel propeller. In some arrangements a plurality of summed-product signals are analyzed to also determine a depth of the detected vessel.

Abstract: A stochastic pulse generator (1) of this invention includes a variable signal generator (61) operative to generate a variable signal (VC) which varies randomly, and a comparator (3) operative to output a binary signal (Vout) of High or Low depending on which of one input signal and another input signal is larger or smaller than the other, wherein when the variable signal (VC) is inputted, as the one input signal, to the comparator (3) from the variable signal generator (61), the comparator (3) stochastically outputs pulses, the number of which corresponds to a magnitude of the another input signal.

Abstract: The invention relates to a method and device for generating data about the mutual position of at least three acoustic transducers. The aim of the invention is to make it possible to continuously measure and calculate the mutual position of at least three acoustic transducers, particularly the rotation and the position of a human head wearing headphones within a room without using any additional transmitter element on the head, headphone, or body of the listener, during audio playback. This aim is achieved by connecting the acoustic transducers to a digitally operated system which comprises an output path emitting audio signals to first and second acoustic transducers, an input path receiving audio signals from the third acoustic transducer, an audio signal source that is connected to the output path, an ultrasound generator that is connected to the output path, and an information generator which indicates a position and is connected to the input path.

Abstract: The present invention relates to a system and a method for substantially eliminating flow noise from the signal output of each hydrophone in a hull mounted acoustic array. The system comprises a plurality of hydrophones forming an acoustic array mounted to a hull of a marine vessel, at least one reference hydrophone mounted to the hull in a laminar region of fluid flow over the hull, and a computational device for generating an output signal for each hydrophone in the acoustic array which is substantially free of flow noise using signals inputted from the acoustic array hydrophones and the at least one reference hydrophone.

Abstract: Provided is a normalizing apparatus for adaptive beamforming by performing a normalizing process which uses a normalized least mean square (NLMS) algorithm that produces a weight vector for adaptive beamforming, in a smart antenna receiver. For the normalizing process, the normalizing apparatus includes a multiplication operation means that performs a multiplication operation, and a division operation means that performs a division operation using mathematic calculations based on binary logarithm principles, and using addition and subtraction operations.

Abstract: An optical position and orientation determining system determines yaw, pitch, roll, lateral translation and longitudinal translation of a body with respect to a direction and intensity sensing receiver. The system comprises two energy beam emitters, mechanically mounted on a body, which illuminate the position sensing receiver. The energy beams are intermittently energized in a predefined fashion to enable the receiver and its associated signal porcessing means to determine the position and orientation of the body with respect to the receiver. The system can also be used to determine velocities and accelerations of the body relative to the receiver.

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

Abstract: A personal direction finding apparatus for determining the direction to be followed in order to reach a predetermined spot which includes a headset provided with two earphones and a circuit for generating a track error signal. The circuit includes a compass supported on the headset for outputting a heading signal corresponding to the heading of the direction of travel, a receiver for a position location and navigation system outputting a signal for the heading to be followed via one output, and a track error computing circuit.

Abstract: A method for determining the positions of the N array elements of a random rray to an accuracy sufficient to accomplish beam forming is provided where the initial positions of the array elements are known to an accuracy of .lambda..sub.min/2, and where .lambda..sub.min is the wavelength of the highest frequency of any of the M cohering sources which are in the field of the array and where the relative directions are unknown. The method includes the steps of: identifying M cohering sources in the field of the array, each of which emits at least one narrowband frequency, each frequency differing from the adjacent frequency by 1/T, where T is the time period of the measurements; a device for measuring the true bearing of one of the M sources; receiving the M cohering signals at the N array elements; performing a Fast Fourier Transform (FFT) on each of the N element signals; examining the spectrum of each of the N received signals; and from the N spectra, selecting M (M>3) lowest angular frequencies, .omega..

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 sound input apparatus according to the present invention subtracts, from the output signal from a first microphone, the output signal of a second microphone which is arranged in a manner different from that of the first microphone to output the subtracted signal and controls the level of the signal of the second microphone in response to the level of the subtracted signal. The sound input apparatus simply constructed in this way achieves a narrowed sound directivity when picking up sound and presents high-quality audio signal while keeping the influence of ambient noise to a minimum.

Abstract: A sound enhancement system including a beamed linear array microphone system for the acoustic pickup of voice and music from substantial distances with a relatively narrow sound pickup beam and with the avoidance of acoustic feedback. The acceptance beam angle is relatively constant over the desired sound octaves. Response outside of the acceptance beam is relatively low. The system includes a microprocessor-controlled circuit for processing the signals from a multiplicity of microphone elements in the linear array for application to a loudspeaker.

Abstract: A microphone selection process is made relatively constant in terms of processing requirements through use of combination values which provide a measure of the quality of the speech signal received in each one of a plurality of microphones. Such combination values are derived in a manner which provides an indication of which one of the plurality of microphones, that provide area coverage for a conference room, for example, best receives the speech signal. In operation, the microphone selection process selects the microphone which best receives the speech signal by comparing a signal energy value received in each one of the microphones to that received in each of the other microphones. More specifically, pairs of microphones are examined, to determine the direction of origin for the speech, by seeking a microphone pair where the speech is strong in the microphone directed toward the source of speech, and weak in an associated microphone directed away from the source of speech.

Abstract: Methods and systems for beamforming are disclosed that include a signal processor that can dynamically determine the relative time delays between a plurality of frequency-dependent signals. The signal processor can adaptively generate a beam signal by aligning the plural frequency-dependent signals according to the relative time delays between the signals. The signal processor can store one frequency-dependent signal as a reference signal and can align the remaining frequency-dependent signals relative to this reference signal. One advantage of the signal processor is that it can align the plural frequency-dependent signals generated by an array of microphones that can be arranged in a linear, two dimensional or three dimensional array and located in a room environment.

Abstract: The present invention-relates to an ultrasonic array imaging system for focusing ultrasonic signals which are reflected from an object to be imaged and received by an array transducer. A digital focusing method and system in accordance with the present invention compensates for phase errors which are contained in digital data by using a quadrature sampling method in digital-processing and focusing of ultrasonic signals. Each of a plurality of delayed-time eliminators receive signals generated by quadrature sampling and removes delayed-time differences from signals. Each of phase compensators receives a digital signal in which a delayed-time difference is removed, and compensates the received digital signal for phase errors. An envelope detector is used to detect an envelope signal using the phase error compensated date.

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

Abstract: An inspection apparatus utilizing a pulse compression technique is described which comprises a signal generator, a transmission/reception probe; first and second correlators and an adder. The signal generator generates a composite transmission signal consisting of signals Sap(t), Saq(t), Sbp(t) and Sbq(t) respectively based on a basic unit signal ga(t) and a sequence {p}, the signal ga(t) and a sequence {q}, a basic unit signal gb(t) and the sequence {p}, and the signal gb(t) and the sequence {q}, to the probe to transmit the composite transmission signal to a target. The first correlator performs a correlation operation of echo signals Rap(t), Raq(t), Rbp(t) and Rbq(t) corresponding to the signal Sap(t), Saq(t) and Sbq(t) by utilizing reference signals Ua(t) and Ub(t) based on the sequences to provide results Caap(t), Caaq(t), Cbbp(t) and Cbbq(t).

Abstract: Hearing aid for persons with an impaired hearing faculty, including a directional microphone whose pick-up characteristic can be altered, the pick-up characteristic being automatically controlled as a function of the input or output signal in such a way that all possible microphone characteristics may be set, and this is realized in that the directional microphone (10) is an electret microphone and that the changes in the pick-up characteristic take place electrically and continuously.

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 square law detection circuit for energy signals such as sonar signals wherein the signal processing eliminates the side lobe detection of false targets by eliminating the side lobes themselves without significant energy degradation of the main lobe of the beam pattern associated with the sonar equipment.

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: A stationary probability integrator system for facilitating spectral anals of detected signals by suppressing random frequency background noise, such as ocean disturbances and marine life, and by enhancing spectral signatures of discrete sound sources, such as generated by submarines in water. A raw 0 to 100 Hertz frequency spectrum of noise and spectral signature from a frequency analyzer having 500 increments or elements is divided into ten assemblies of 50 elements per ensemble. The ensemble averages, which are the average simultaneous energy levels of all elements in respective ensembles, of each sample is negatively combined with the energy level of each element of the corresponding ensemble of the next consecutive raw sample. Each combination and the cumulative algebraic sum of each combination is then displayed in the same frequency spectrum as the samples.

Abstract: A radiant energy detector having a pair of receiving transducers, a pair of ariable gain amplifiers connected to said transducers for amplifying the outputs thereof different amounts, a subtract circuit for producing a signal representing the difference of said amplifier gains, a Schmitt trigger which is triggered by said difference signal whenever it exceeds a predetermined value, and an And gate connected to the outputs of said pair of amplifiers and the output of said Schmitt trigger for producing a utilization signal whenever all thereof occurs simultaneously.

Abstract: A planar end-fire acoustic transducer array is composed of a planar matrix f individual elements. In order to give this array an end-fire characteristic, predetermined elements are provided with outputs which are phase-inverted with respect to the outputs of the other elements of the array, the sum of the gains of these predetermined elements being made equal to the sum of the gains of the other elements.

Abstract: A system which measures direct current drift and noise in sensor signals from redundant sensors utilizing a parity-space algorithm. Parity vector signals produced by the parity-space algorithm are averaged to provide a direct current (DC) drift signal. An instantaneous noise signal is found by subtracting the direct current drift signal from a parity vector signal for one of the samples of the sensor signals. The RMS value of the instantaneous noise signals are averaged to provide sensors noise signals.

Abstract: A directional microphone apparatus includes an array of at least three sets of microphone units, circuits for processing the output signals from the microphone units to produce a first signal which varies in accordance with the second order bidirectional sound pressure gradient characteristic of the array, weighting circuits for applying respective weighting coefficients to the output signals from the microphone units in accordance with a desired shape of directivity response characteristic, to produce corresponding weighted signals which are combined to form a second signal. The first and second signals are combined to produce an output signal which exhibits sharp directivity even at relatively low frequencies in the audio range.

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.