Abstract: A system and method for eliminating confusion associated with checking valves, wherein additional test points are added to the measurement of a valve for ensuring the verification of the actual sources of leaks or turbulence. A base line measurement for the valve is established by measuring the level of ultrasonic sound at the two points upstream from the valve. The level of the ultrasound at two downstream points is then measured. The value of the ultrasound at the downstream test points is compared to the values of the ultrasound at the upstream test points. If the values of ultrasound at the downstream test points are higher than the values of the ultrasound at the upstream test points, then the valve is leaking. If the values of the ultrasound at the downstream test points are close to or lower than the values of the ultrasound at the upstream test points, then the valve is not leaking, i.e., the valve is good.

Abstract: A focal point reflector is used in conjunction with a dual heterodyne circuit to reduce reception nulls that can occur when performing ultrasonic measurements. The focal plane reflector is a flat non-porous or reflective material, such as printed circuit board (PCB) that is placed behind and in parallel with an ultrasonic array of piezoelectric transducers. In accordance with the invention, the addition of the focal point reflector to the array of piezoelectric array permits the reflection of ultrasonic energy that may “fall” between the crystals in the array and then back into the crystal elements.

Abstract: An ultrasonic coding modem for digital network communication comprises a transmitting device having a first piezoelectric substrate, and a receiving device having a second piezoelectric substrate. If a message digital-signal is applied to the transmitting device, a SAW is excited on the first piezoelectric substrate and is delivered as a coded digital signal into a digital network. On the other hand, if the coded digital-signal is received at the receiving device from the digital network, a SAW is excited on the second piezoelectric substrate. In this time, if the SAW excited on the second piezoelectric substrate is corresponding to the SAW excited on the first piezoelectric substrate, an output digital-signal, which is equivalent to the message digital-signal, is delivered from the receiving device. As a result, it is possible to keep a base-band communication secret.

Abstract: A method and apparatus for detecting leaks and mechanical faults by way of an ultrasonic device. An output from a variable gain amplifier is supplied to a pair of heterodyning circuits, i.e., a dual heterodyning circuit. At each respective heterodyning circuit, the output signal from the variable gain amplifier is multiplied by a local oscillator that is internal to each circuit. The dual heterodyning circuit is used to provide an enhanced input transducer signal for spectral analysis. This permits the capture of low level frequency components for extraction during spectral analysis. The dual heterodyning circuit of the present invention to provide the enhanced spectrum to thereby permit an easy determination of whether the resonance is mechanical or electrical becomes clear. In addition, fault frequencies are also more easily discernable. In other words, the enhanced signal output provides a lower signal to noise ratio such that the ease with which frequency components are analyzed is increased.

Abstract: A method and apparatus for detecting and locating leaks in buried pipes is disclosed in which ground penetrating radar, induction, acoustic, and vacuum excavation systems are selected based on soil conditions and then employed in selected combinations. The conductivity and wave speed of the soil are used in the selection process and in the process of detecting and locating a leak based on the measurements obtained from the selected combination of detection systems.

Abstract: An acoustic signal processor that samples acoustic data, performs a spectrum analysis of the sampled acoustic data, stores the acoustic data in corresponding frequency bins, and then filters acoustic data stored in a frequency bin by applying a power-law arithmetic operation to the frequency bin acoustic data, such that the power-law arithmetic operation is adaptively changed based on an order dependent determination of whether the frequency bin acoustic data is representative of noise or clutter, or whether it is representative of a signal of an object.

Abstract: A transmit-receive (T-R) switch for achieving fast T-R switching times while ensuring that the signal strength of a received signal is not fully coupled. A differential amplifier and an inverting amplifier, both having a coupling resistor as an input is used so that nearly all of the input signal is sensed by an operational amplifier. This technique improves transducer voltage transfer (coupling) ratio from 15-24% to about 100%. The T-R switch architecture is preferably to short-range, single-transducer acoustic ranging systems.

Abstract: A signal processing system provides and processes a digital signal, converted from to an analog signal, which includes a noise component and possibly also an information component comprising small samples representing four mutually orthogonal items of measurement information representable as a sample point in a symbolic Cartesian four-dimensional spatial reference system. An information processing sub-system receives said digital signal and processes it to extract the information component. A noise likelihood determination sub-system receives the digital signal and generates a random noise assessment of whether or not the digital signal comprises solely random noise, and if not, generates an assessment of degree-of-randomness. The information processing system is illustrated as combat control equipment for undersea warfare, which utilizes a sonar signal produced by a towed linear transducer array, and whose mode operation employs four mutually orthogonal items of measurement information.

Abstract: A system and process for localizing signals received on multiple co-linear arrays reduces the adverse effects on localization performance due to background noise. The system and process coherently combine all possible array cross-correlograms. The resulting correlogram is a function of two variables, one which corresponds to a fine bearing estimate and a second with maps into range.

Abstract: The present invention provides signification improvements over the apparatus and method disclosed by U.S. Pat. No. 4,922,467. The invention provides an apparatus for material classification and substance identification of an object contained within an enclosure, or buried beneath the ground. The improvements to the present invention include the use of a source of either electromagnetic or acoustic energy, and electromagnetic or acoustic energy receivers, as appropriate. In addition, the present invention discloses the use of energy pulses of differing frequencies, such that the signal processor can compute the rate of change of energy absorption of the substance, as a function of frequency (d&agr;/df). In this way, the apparatus permits the formulation of a highly detailed and accurate object signature, which can be compared with a database of known object signatures for exact substance identification.

Abstract: For use with a high gain receiver circuit which receives echo pulses of frequencies within a predetermined bandwidth and at times within interpulse periods of a predetermined pulse repetition rate and amplifies the echo pulses for measurement purposes, the receiver circuit susceptible to electrical noise within the frequency bandwidth of the received echo pulses to create false echo pulses, a method of eliminating substantially the false echo pulses without affecting substantially the amplified echo pulses by accepting only echo pulses which occur synchronously among interpulse periods. The pulse repetition rate may be varied to eliminate false echo pulses that are synchronous to the interpulse periods.

Abstract: A signal processing system provides and processes a digital signal, converted from to an analog signal, which includes a noise component and possibly also an information component comprising small samples representing four mutually orthogonal items of measurement information representable as a sample point in a symbolic Cartesian four-dimensional spatial reference system. An information processing sub-system receives said digital signal and processes it to extract the information component. A noise likelihood determination sub-system receives the digital signal and generates a random noise assessment of whether or not the digital signal comprises solely random noise, and if not, generates an assessment of degree-of-randomness. The information processing system is illustrated as combat control equipment for undersea warfare, which utilizes a sonar signal produced by a towed linear transducer array, and whose mode operation employs four mutually orthogonal items of measurement information.

Abstract: An acoustic signal processor that samples acoustic data, performs a spectrum analysis of the sampled acoustic data, stores the acoustic data in corresponding frequency bins, and then filters acoustic data stored in a frequency bin by applying a power-law arithmetic operation to the frequency bin acoustic data, such that the power-law arithmetic operation is adaptively changed based on an order dependent determination of whether the frequency bin acoustic data is representative of noise or clutter, or whether it is representative of a signal of an object.

Abstract: An underwater acoustic sensor system for detecting and efficiently displaying data from small, shallow-draft targets at high speeds in shallow or very shallow water. Sonar buoys transmit electrical signals representing sound pressure waves, which are processed to ascertain bearing and signature information for a detected object. A single display having a bearing history area, a frequency history area, and a bearing/frequency area, provide a system operator with efficient correlation between bearing and frequency data.

Abstract: The present invention is directed to a method and system for significantly reducing the acoustic noise from near-surface sources using an array processing technique that utilizes Multiple Signal Classification (MUSIC) beamforming and the Lloyd's Mirror interference pattern at very low frequencies. Noise from nearby near-surface sources, such as merchant ships, super tankers, fishing trawlers, seismic profiling platforms, or other sources near the ocean surface can significantly interfere with the detection and tracking of a quiet target-of-interest (TOI) located well below the ocean surface. The present invention reduces the noise of the near-surface sources without degrading the signal level and quality of the TOI. The present invention utilizes a unique application of the MUSIC beamforming process to separate the noise and signal subspace. Next, eigenvalue beamforming is used to reduce narrowband energy in selected frequency bins wherein the near-surface noise is radiating.

Abstract: A method for producing, from passive sonar data, operational images interactively controlled by an operator, continuously adjusted according to operational requirements and compatible with changing information requirements in real time. The invention uses a method for representing a multidimensional data field on a display screen which uses the screen co-ordinates for two dimensions of data and at least one of three color perception components among luminosity, hue and saturation for three other dimensions of the data, to produce bearing-time, azimuth-time, or frequency-time (circulating lofar) or frequency-bearing images with representation of frequencies by hue or interactive filtering.

Abstract: A method for characterizing degree of phase fluctuation of a signal and a signal processor for accomplishing such characterization, is described, in which a time series of complex data vectors are received, initial spectral processing is accomplished, an estimate of the excess phase rotation is made, and a quantity WSC equal to WSC = [ 1 M ⁢ ∑ i = 3 N ⁢ B ⁡ [ C ⁢   ⁢ Φ i ] L ] is calculated.

Abstract: A nonlinear signal processing system and method is used to identify nonlinearity (e.g., chaos) in underwater acoustic signals, such as sonar signals. The system and method detects the underwater acoustic signal and digitizes the underwater acoustic signal to produce an acoustic time series. The acoustic time series is reconstructed using a phase space embedding algorithm to generate a phase space embedded acoustic signal. A differential radius signal is generated from the phase space embedded acoustic signal using chaotic radius computations and differential radius computations. Thresholds can be detected in the differential radius signal to reveal nonlinear or chaotic events hidden in the underwater acoustic signal.

Abstract: The present invention discloses an integrated circuit receiver available for infrared or ultrasonic transmission by use of digital filtering for demodulation of infrared or ultrasonic carrier signal. The integrated circuit receiver comprises an infrared receiver or ultrasonic transducer to receive the transmitted signal from outside and output the modulated signal. The modulated or carrier signal is fed to an amplifier circuit to be amplified and then outputted to a digital filter to filter out the carrier from the amplified signal, and thus the original or unmodulated signal is recovered. The filtering thereof is done by a digital filter instead of an analog one, therefore there is no need for discrete devices such as capacitors, resistors, diodes and inductor, and it is suitable to be integrated within a chip as an apparatus to receive and detect infrared and ultrasonic signals.

Abstract: A novel method and apparatus for signal processing are described which discriminate between signals and noise based on the magnitude of the phase fluctuations. In an embodiment of the invention, the governing equations of the process adaptively change in response to the phase and amplitude characteristics of the signals being received for processing. In an embodiment of the invention, an automatic detection method and apparatus is described which has the capability to alert an operator of the presence of signals having phase fluctuation characteristics which match a set of preset conditions (e.g. small fluctuations, medium fluctuations, or large fluctuations).

Abstract: A multidimensional beamforming device that performs consecutive one-dimensional operations. For example, beamsteering for a two-dimensional array can be include a projection of a beam onto each of the respective axes of the array. In such a device, a first beamforming processing element is used to form multiple beams for each array output along a given row. In a preferred embodiment, sequential output vectors from the first processing element are then applied to a transposing or corner turning memory and the data are reformatted such that all elements on a given column of the array are applied to a second beam forming processing element.

Abstract: A severe weather detection apparatus for detecting severe weather and method of detecting and warning of approaching severe weather conditions is provided. The severe weather detector apparatus includes a barometric pressure sensor and computerized means for calculating the rate of change in the barometric pressure. By monitoring and deriving a value representative of the rate of change in the barometric pressure over time, a threshold is established and compared to the current rate of change in the barometric pressure. The derived rate of change is compared to a value stored in the device which reflects approaching severe weather conditions. Rates of change which may indicate the approach of severe weather activate a voice-enunciated alarm that announces the potentially dangerous barometric activity. The severe weather detection apparatus is portable and suitable for battery power and installation in the same manner as a home smoke alarm or carbon monoxide detector.

Abstract: In the method according to the invention, several adjacent synchronized ultrasonic sensors automatically generate a clock signal with measurement clocks (M1, M2, M3). The transmission pulses (S1, S2, S3) of three ultrasonic sensors are generated with changing transmission pulse offset (d1, d2, d3) with respect to the respective measurement clocks (M1, M2, M3). Thereby, extrinsic echo signals of adjacent ultrasonic sensors can be masked out since only these echo signals change their position relative to the transmission pulses (S1, S2, S3). In contrast, the actual sought echo signal does not change its respective position relative to the transmission pulse (S1, S2, S3).

Abstract: A system for detecting an object of interest through a medium such as the atmosphere or ocean employs a reference object from which a reference signal emanates. A detector detects and transforms the reference signal into a transformed reference signal and further detects and transforms an object signal emanating from an object of interest into a transformed object signal. The object signal may be radiated, re-radiated, or scattered from the object of interest. An image processor generates a corrected image signal by applying an image transfer function to convolve the transformed object signal. Then a display presents a corrected image of the object of interest in response to receiving the corrected image signal.

Abstract: The circuit and the method serve to transmit a transmission signal to a transducer and to receive a reception signal from the transducer. The transmitter and the receiver are each alternatively coupled to the transducer and decoupled from one another. The coupling and decoupling is thereby achieved by a total of three nonlinear two-terminal networks (Z1, Z2, Z3). The transmitter is connected to the transducer via a bipolar voltage limiter and the receiver is connected to the transducer via a bipolar current limiter.

Abstract: A method and an apparatus for distinguishing systematic artifacts from noise involves localizing functional noise in the vicinity of predicted functional peaks. The method is particularly relevant to detection and tracking of time-varying signals. An apparatus implementing such an application of the method comprises a detection system (50) which monitors each component of a multi-component periodic signal via its basis repeat unit: a cyclet, of periodicity &tgr;. The signal is digitized and clocked through the system (50) in segments. A cyclet remover (62) subtracts predicted values of previously detected cyclets from the incoming signal segment to produce a residual signal. A cyclet detector (60) uses a sliding window procedure to detect further cyclets in this residual and to measure their amplitude profiles {overscore (b)}(&tgr;) and periodicities (&tgr;).

Abstract: The invention relates to a method of screening an acoustic signal or a spectrum line of maximum energy transmitted by a “target” that can be submerged at sea, from among a multitude of acoustic signals coming from any noise generators radiating acoustic signals of the same type with higher energy than energy E, employing, for example, (1) a set of N submersible acoustic pickups identically parameterized in surveillance mode, designed to detect the presence of the signal or a desired spectrum line, with the set of N pickups defining any number of surveillance cells with two adjacent pickups, each pickup being associated with one or more target detection regions defined as the geographic areas within which the presence of the “target” is deemed detectable and outside which the “target” is deemed nondetectable, and (2) a maximum number Nmax of pickups relating to one or more “special” areas (selected from a set of elementary geographic areas) of a given surveillanc

Abstract: A method and an apparatus are provided for matching the response of hydrophones 22 to the response of geophones 24 and significantly reducing response variations between hydrophones caused by inherent characteristics. The method includes the steps of determining a capacitance 66 for each of the hydrophones 22 in an operating environment, configuring a filter 36 based on the capacitance 66, and modifying a response of a channel of the hydrophone 22 using the filter 36. The apparatus includes an acquisition unit 20 having a geophone 24 and a hydrophone 22, a recording unit 30, a processing unit 31 and a filter 36 for correcting for variation between hydrophones 22 and changing a first order low frequency response of the hydrophone 22 to appear like a second order response like that of the geophone 24.

Abstract: An acoustic signature recognition and identification system receives signals from a sensor placed on a designated piece of equipment. The acoustic data is digitized and processed, via a Fast Fourier Transform routine, to create a spectrogram image of frequency versus time. The spectrogram image is then normalized to permit acoustic pattern recognition regardless of the surrounding environment or magnitude of the acoustic signal. A feature extractor then detects, tracks and characterizes the lines which form the spectrogram. Specifically, the lines are detected via a KY process that is applied to each pixel in the line. A blob coloring process then groups spatially connected pixels into a single signal object. The harmonic content of the lines is then determined and compared with stored templates of known acoustic signatures to ascertain the type of machinery. An alert is then generated in response to the recognized and identified machinery.

Abstract: A signal detector for monitoring sound signals comprises a first sensor operative in response to sound signals to produce a first electrical signal, first processing circuitry operative in response to the first electrical signal to amplify it and produce a first input signal, digitally controlled oscillator circuitry operative to produce a reference signal at a selected reference signal frequency, a mixer operative to receive the first input signal and reference signal to produce a mixed composite signal, conditioning circuitry operative in response to the mixed composite signal to produce a first amplified output signal, and a first output device for producing a first display in response to the first amplified output signal. A methodology is also provided for monitoring sound signals in order to indicate a presence of those signals having frequencies within a selected range.

Abstract: The invention relates to a device for measuring noise comprising a sensor circuit having at least two sensors, an ambient noise eliminating circuit and a signal processing circuit. All the sensors are set to detect the ambient or background noise, however the source noise is positioned for detection by one of the sensors. The output of the sensor circuit is connected to the input of the ambient noise eliminating circuit where the ambient noise is eliminated from the noise signal leaving only a signal of the noise source. The signal processing circuit receives the signal of the measured noise, which is rectified and amplified, and then processed in the comparator circuit to determine whether the noise level is acceptable or not. The result is displayed through the display circuit comprising a plurality of LEDs.

Abstract: A data acquisition system receives an analog input signal comprising a pllity of octavely-nested components including a base octave and a selected number of higher-level octaves, and transmits digital data words representative of each component over a channel. The data acquisition system includes a data transmission system and an interface. The data transmission controller generates transmission strobes signals defining a series of octave transmission cycles each associated with one of said octaves, each octave transmission cycle having a series of octave strobe states including at least one octave strobe state associated with the base octave and successively higher numbers of octave strobe states associated with successively higher-level octaves. The transmission strobe states associated with each octave are uniformly distributed during each octave transmission cycle.

Abstract: A receiver and method are disclosed that improves signal detection in a mipath environment wherein the desired reflected acoustic pulse is degraded by multipath reflections and embedded in noise. The invention provides a receiver that repetitively processes the received signal. The receiver includes separate signal processors, such as parallel configured quadrature signal processors, wherein each processor operates over different, and preferably contiguous, time intervals. After each repetition, the processing time interval for each processor is changed. The outputs of the processors are combined, such as by summing, and applied to a detector, such as a threshold detector, for each processing repetition to determine if the transmitted pulse is detected. The receiver continues processing the received signal until a predetermined number of time intervals have been processed without detection of a pulse or until the reflected pulse is detected.

Abstract: An apparatus for accurately transmitting and receiving acoustic waves indoors is provided. The apparatus contains a microphone, a speaker, a processing circuit, a first amplifier, a second amplifier, and a power control circuit. The microphone converts an input acoustic wave into an electric signal, and the speaker generates an output acoustic wave based on input data. The processing circuit processes the electric signal to produce processed data and outputs the input data to drive the speaker. The first amplifier receives a power signal and detects if a starting signal is contained in the electric signal output from the speaker. Then, the amplifier outputs a first detection signal when the starting signal is detected and outputs the power signal when the first detection signal is output. The second amplifier receives the power signal from the first amplifier and detects if a non-starting signal is contained in the electric signal when the starting signal is detected.

Abstract: An apparatus and method for filtering the effects of large amplitude signal fluctuations from elements of the cross-spectral density matrix of a detor array. The outputs of the array are sampled T times, and the values of each element of the matrix formed by using: ##EQU1## where Z.sub.li is the complex output of an sensor of the array at time i; Z*.sub.mi is the complex conjugate of the output of an array sensor at said time i; and k is an integer greater than 1. Because of the exponent k, small, relatively constant, terms will dominate, reducing the effect of large amplitude fluctuations. Preferably, the above value will be scaled according to: ##EQU2## which, besides being similarly filtered by the exponential terms, the resultant matrix element will have a magnitude corresponding to the actual power of the detected signal, after filtering.

Abstract: In accordance with the present invention, a method for obtaining frequency nformation about a given data set is realized. The method comprises the steps of providing a processing unit; inputting a raw data set into the processing unit; optionally removing at least one trend from the raw data; ordering the raw data; estimating power spectral density using an eigenanalysis approach and the inputted raw data and the ordered raw data; simultaneously estimating the power spectral density using the raw data and a periodogram; generating a time-series representation of the raw data to which curve fitting is applied; comparing the results from the power spectral density estimating steps and the time-series representation generating step to determine if any frequencies suggested by the eigenanalysis approach estimating step are valid; and generating an output signal representative of each valid frequency.

Abstract: In a noise measuring system comprising a microphone array and a directivity forming section for controlling the direction of directivity of the microphone array, the directivity forming section includes delay section and adding section, and the optimal value of a delay time of the delay section is set in such a manner that a noise isolation characteristic for causing any mobile noise generator not targeted for noise measurement to come off a directional plane or a directional line formed in the direction of directivity of the microphone array and a deterioration characteristic of the directivity of the microphone array balance with each other.

Abstract: The present invention generally relates to procedures and apparatus for monitoring incoming signals to detect the presence of selected target signals contained within the universe of signals received. More particularly, the present invention is directed to monitoring audio signals to detect selected ultrasonic and sonic signals in an ambient environment. Thus, the present invention is even more specifically directed to leak detectors and bearing wear indicators and methods for detecting sound signals which either travel in the air or are present in solids.

Abstract: A layered structure is divided into a plurality of regions. Transmission line equivalents (Green's functions) in the spectral domain are formed between all regions within the layered structure. The spectral domain Greens' function are converted to the spatial domain using a near field and a far field computed for those regions part of a component within the layered structure. The far field is extracted from a compressed database computed from the transmission line equivalents and descriptive of the layered structure. The near field is computed using a prioritization mechanism. Priority is assigned in accordance with the amplitude of a source and the length of the path between regions of interest.Once the physical characteristics of the layers used in the fabrication process of the IC are identified, the database used for computation of the far field is compiled and compressed, and remains unchanged for each new parameter extraction.

Abstract: A method and an apparatus for enhancing the side-lobe performance of a sparse ultrasonic transducer array using harmonic imaging to reduce all beam sidelobe (including grating lobe) levels. Harmonic imaging consists of using the active transducer elements to transmit an ultrasound signal (wideband or narrowband) of center frequency f.sub.0 and receive at one or more harmonic frequencies nf.sub.0, where n.gtoreq.2.

Abstract: An acoustic communication apparatus includes a microphone/speaker for converting a power voltage and an aerial acoustic wave into an electric signal, and generating an acoustic wave corresponding to the input of data; a signal processing circuit for signal processing the electric signal output from the microphone/speaker in response to the input of the power voltage, the signal being received as data, the circuit outputting data responding thereto to thereby drive the microphone/speaker; a starting signal selection amplifier for always receiving the power voltage during a reception waiting mode, and detecting a starting signal having a predetermined frequency from the electric signal output from the speaker; a non-starting signal selection amplifier for receiving the power voltage in response to the detection of the starting signal, and selectively amplifying only a band excluding the frequency band of the starting signal; and a power voltage supply control circuit for supplying the power voltage to the signa

Abstract: A rugged ultrasonic sensor is provided which is capable of detecting objects in very close proximity to the sensor. This close proximity detection includes the detection of objects which are immediately adjacent the sensor housing. Such close range operation is achieved by tailoring the transducer to operate at previously undesirable conditions, including low Q and high frequency. Such operating conditions allow the resonating characteristics of the transducer not to interfere with close range operation.

Abstract: A likelihood of detecting a reflected signal characterized by phase discontinuities and background noise is enhanced by utilizing neural networks to identify coherency intervals. The received signal is processed into a predetermined format such as a digital time series. Neural networks perform different tests over arbitrary testing intervals to determine the likelihood of a phase discontinuity occurring in any such interval. An integration time generator subsequently uses this information to define a series of contiguous coherency intervals over the duration of the received signal. These coherency intervals are then used for piece-wise processing of the received signal by parallel quadrature receivers. The outputs are combined and processed for detecting the presence of the reflected signal.

Abstract: A method for enhancing signal-to-noise ratio and resolution of amplitude stable signals wherein underwater acoustic data is first collected with an array of hydrophones, and then the data is digitally sampled. After producing spectra of sequential time snapshots of the digitally-sampled data, the spectra are beamformed for a single frequency. Next the low resolution beamformer response is deconvolved from the data by use of a calculated beam response pattern for the hydrophone array, so that many high-resolution estimates are created for each time snapshot. Finally, the resulting high resolution estimates are reduced to a single estimate for each spatial bin across all of the time snapshots, and the high resolution, high gain results are displayed.

Abstract: Traffic is monitored in individual lanes of a roadway as to vehicle count or presence, speed and direction of movement by mounting a microphone array high above the road surface, digitizing the output signals of the microphones, filtering, beamforming and storing the digitized signals to provide separate power histories for separate locations in individual lanes. These power histories are then analyzed to provide vehicle movement data for each lane.

Abstract: A method and apparatus for reducing the effects of noise on a system for measuring physiological parameters, such as, for example, a pulse oximeter. The method and apparatus of the invention take into account the physical limitations on various physiological parameters being monitored when weighting and averaging a series of measurements. Varying weights are assigned different measurements, measurements are rejected, and the averaging period is adjusted according to the reliability of the measurements. Similarly, calculated values derived from analyzing the measurements are also assigned varying weights and averaged over adjustable periods. More specifically, a general class of filters such as, for example, Kalman filters, is employed in processing the measurements and calculated values. The filters use mathematical models which describe how the physiological parameters change in time, and how these parameters relate to measurement in a noisy environment.

Abstract: A novel multi-lane traffic monitoring system is based on detecting the acoustic signals motor vehicles create and radiate during operation. The system comprises an array of electro-acoustic sensors for converting impinging acoustic wavefronts to analog electrical signals; a circuit to acquire, perform signal frequency component discrimination, and digitize the electrical signals at the electro-acoustic sensor array output; a circuit to perform effective spatial discrimination in the up/down road direction and in the cross-road direction in real time; a circuit to perform vehicle detection for individual lanes and to estimate or measure pertinent parameters associated with each vehicle detection from each traveled lane; and a circuit to compute for each lane, pertinent traffic flow parameters from vehicle parameters for the purpose of providing a transportation system interface.

Abstract: A method for finding a probability density function (PDF) and its statistical moments for an arbitrary exponential function of the form g(x)=.alpha.x.sup.m e.sup.-.beta.x.spsp.n,0<x<.infin., where .alpha., .beta., n>0, m>-1 are real constants in one-dimensional distributions and g(x.sub.1,x.sub.2, . . . ,x.sub.l) in the hyperplane. Non-linear regression analyses are performed on the data distribution and a root-mean-square (RMS) is calculated and recorded for each solution set until convergence. The basis function is reconstructed from the estimates in the final solution set and a PDF is obtained. The moment generating function (MGF), which characterizes any statistical moment of the distribution, is obtained using a novel function derived by the inventors and the mean and variance are obtained in standard fashion.

Abstract: A chaotic signal processing system receives an input signal provided by a nsor in a chaotic environment and performs a processing operation in connection therewith to provide an output useful in identifying one of a plurality of chaotic processes in the chaotic environment. The chaotic signal processing system comprises an input section, a processing section and a control section. The input section is responsive to input data selection information for providing a digital data stream selectively representative of the input signal provided by the sensor or a synthetic input representative of a selected chaotic process. The processing section includes a plurality of processing modules each for receiving the digital data stream from the input means and for generating therefrom an output useful in identifying one of a plurality of chaotic processes. The processing section is responsive to processing selection information to select one of the plurality of processing modules to provide the output.

Abstract: A method and system are provided for frequency filtering compressional wave nergy. An elastic cylinder is filled with a fluid that is selected based on a fluid density .rho..sub.i and a dilatational wave phase velocity c.sub.i thereof. When the elastic cylinder so-filled is subjected to a compressional wave propagating in a fluid environment, a first radial resonance frequency of the elastic cylinder is controlled by the fluid density .rho..sub.i and the dilatational wave phase velocity c.sub.i. Further tuning of the first radial resonance frequency can be achieved by adjusting the radial wall thickness of the elastic cylinder.