Abstract: There is described a method for communicating data, the method comprising: receiving an incomplete data stream, wherein the incomplete data stream comprises a plurality of sequences of data points having respective values and a plurality of sequences of missing data points; receiving a missing data model; determining values for each of the plurality of sequences of missing data points, comprising: selecting a sequence of missing data points that has not previously been processed, wherein the sequence of missing data points to be processed is selected as a smallest sequence of missing data points of the plurality of sequences of missing data points that have not previously been processed; processing the incomplete data stream to determine values for the selected sequence of missing data points based upon the missing data model; updating the incomplete data stream to include the determined values for the selected sequence of missing data points; and wherein values for subsequent sequences of missing data points

Abstract: Proposed is a space monitoring apparatus using a sound signal and a space monitoring method thereof and, more specifically, is a technology in which a space monitoring apparatus using a sound to determine a spatial condition sets a synthesized sound having a plurality of frequency components to utilize the performance of a speaker efficiently and emits the synthesized sound to monitor the spatial condition.

Abstract: There are provided a sound source visualization device and method. A sound source visualization device according to an embodiment includes: a sound source detection module configured to detect a sound source signal by using a plurality of sound source detection sensors; a preprocessing module configured to filter out the noise and amplify the sound source signal; a calculation module configured to calculate an approximate sound source location by analyzing the preprocessed sound source signal; a search module configured to generate a plurality of pseudo-planes by using the altitude information, to select planes, and to generate three-dimensional sound source location and altitude information by including information, obtained using the selected planes, in the approximate sound source location; and a visualization module configured to output sound source information to a preset system host or to convert this sound source information into a visualization signal and display the visualized signal.

Abstract: An ultrasonic-based person detection method. The method comprising the steps of: (a) emitting, from an emitter, an ultrasonic signal, the ultrasonic signal including a component at a first frequency; (b) receiving reflections of the ultrasonic signal, the received signal including components at frequencies greater than and less than the first frequency; (c) determining a difference between an upper portion of the received signal containing a frequency higher than the first frequency, and a lower portion of the received signal containing a frequency lower than the first frequency; and (d) determining, based on the difference between the upper portion and the lower portion, whether a person is present.

Abstract: The various implementations disclosed herein pertain to methods and systems for detecting a state of monitored objects in a premises. In one aspect, a method is performed at a computer system that is communicably coupled to sensor devices. The computer system receives and processes information of acoustic signals against a database of stored acoustic signatures characterizing predefined acoustic signals generated by electrically non-powered passive tags in response to physical motion of respective monitored objects associated with the passive tags. It receives a first acoustic signal characterized by a first acoustic signature and generated by a first passive tag. In response to the receiving, based on the first acoustic signature and information in the database, it identifies the first monitored object associated with the first acoustic signature, determines a first state of the first monitored object, and provides a notification of the first state to an occupant of the premises.

Abstract: An inverted group delay circuit is provided. The inverted group delay circuit can offset a group delay between a pair of signals. In a non-limiting example, the inverted group delay circuit can be configured to offset a group delay (e.g., negative group delay) between a time-variant voltage and a time-variant envelope of an analog signal. More specifically, the inverted group delay circuit can output an inverted time-variant voltage having an opposing phase and time-adjusted relative to the time-variant voltage to thereby offset the group delay between the time-variant voltage and the time-variant envelope. As such, the inverted group delay circuit can be provided in a power management integrated circuit (PMIC) to improve timing alignment between a time-variant voltage(s) and a time-variant analog signal(s) at a power amplifier(s), thus helping to reduce potential amplitude distortion when the analog signal(s) is amplified by the power amplifier(s).

Abstract: A radar system and method include a sparse array receive element and a processing device. The system performs a beamforming operation on a received radar signal to generate a beamforming spectrum, which contains superposed impulse responses with relative power and angle. The processing device executes an iterative detection routine, starting with a first stage detection that compares the beamforming spectrum to an active power threshold and identifies tentative detection points. In the second stage detection, the processing device determines a certain detection point with the greatest relative power and updates the active power threshold for subsequent iterations of the detection routine. The update involves centering the impulse response related to the certain detection point around its angle, multiplying the relative power by the impulse response, and summing the product with the active power threshold. This process continues until a final set of detection points is obtained.

Abstract: A method for monitoring the take-off and/or landing procedure of an aircraft (1), in particular for an electrical, vertical take-off and landing aircraft (1), in which a monitoring region of a take-off and landing site (2) is monitored by at least one microphone (4, 5) of a monitoring station to detect sound emission data of an aircraft (1) taking off or landing as it approaches or departs and the detected sound emission data are transmitted from the monitoring station to an evaluation unit. The detected sound emission data are evaluated by the evaluation unit by comparing the detected sound emission data to characteristic sound emission data.

Abstract: A method of assuring integrity of range measurements and position solutions comprises obtaining range measurement statistics between network nodes, performing a snapshot integrity test for the range measurement statistics, and performing a sequential integrity test using the range measurement statistics. The snapshot integrity test comprises using Gram matrices with a current configuration of the nodes; performing a singular value consistency check using the Gram matrices against a user selected threshold; and detecting and excluding range measurement statistics with instantaneous errors that cause the singular value to exceed the threshold.

Abstract: An aircraft noise monitoring system uses a set of geographically distributed noise sensors to receive data corresponding to events captured by the noise sensors. Each event corresponds to noise that exceeds a threshold level. For each event, the system will receive a classification of the event as an aircraft noise event or a non-aircraft noise event. It will then use the data corresponding to the events and the received classifications to train a convolutional neural network (CNN) in a classification process. After training, when the system receives a new noise event, it will use the CNN to classify the new noise event as an aircraft noise event or a non-aircraft noise event, and it will generate an output indicating whether the new noise event is an aircraft noise event or a non-aircraft noise event.

Abstract: A terrestrial acoustic sensor array for detecting and preventing airspace collision with an unmanned aerial vehicle (UAV) includes a plurality of ground-based acoustic sensor installations, each of the acoustic sensor installations including a sub-array of microphones. The terrestrial acoustic sensor array may further include a processor for detecting an aircraft based on sensor data collected from the microphones of at least one of the plurality of acoustic sensor installations and a network link for transmitting a signal based on the detection of the aircraft to a control system of the UAV.

Abstract: A method for classifying a response signal of acceleration data of a structure includes obtaining at least one signal feature of a response signal, inputting the at least one signal feature into an artificial neural network, and classifying, using the artificial neural network, the response signal as an impact event or a non-impact event. One or more signal features may be used, including a response length feature, a number of peaks feature, a spectral energy feature, a dominant frequency feature, a maximum response feature, a center of mass feature, a slope feature, an average peak power feature, a response symmetry feature, or combinations thereof. One or more artificial neural networks may be used. The artificial neural networks may be trained using different combinations of signal features.

Abstract: A headset for acoustic authentication of a user is provided, the headset comprising at least a first microphone, a second microphone, a controllable filter, and an authenticator. The first microphone is arranged to obtain a first input signal. The second microphone is arranged to obtain a second input signal. The controllable filter is configured to receive the first input signal and the second input signal and to determine at least one filter transfer function from the received first input signal and the second input signal. The authenticator is configured to determine a current user acoustic signature from the at least one filter transfer function and to compare the current user acoustic signature with a predefined user acoustic signature and to authenticate the user based on the comparison of the current user acoustic signature with the predefined user acoustic signature.

Abstract: Described herein is a system for device arbitration using characteristics of audio data captured by multiple devices. The system determines a feature vector corresponding to each device that captured an audio input, where the feature vector includes the audio energy levels, spectral data corresponding to the audio data and centroid data corresponding to the audio data. The feature vectors are processed using a trained component to select a device for further processing.

Abstract: A sound signal corresponding to a sound emitted by a sound source is inputted to a frequency analysis unit (101), and the frequency analysis unit (101) performs frequency analysis of the sound signal and generates a spectrogram. Spectrogram template information indicating spectrograms corresponding to each of at least a plurality of predetermined movement speeds, the spectrograms being for cases in which the sound source is moved, is stored in a model storage unit (102). An estimation unit (103) estimates the movement speed of the sound source on the basis of the spectrogram generated by the frequency analysis unit (101) and the plurality of spectrograms indicated by the spectrogram template information stored in the model storage unit (102).

Abstract: Systems and apparatuses for generating customized user output are provided. The system may collect sensor data, associated with the user, from a variety of sources. The system may use the sensor data to generate a customized user output. The system may analyze the sensor data, and determine, based on the sensor data and the customized user output, one or more user recommendation outputs. The system may update the customized user output based on additional or subsequent sensor data, and/or based on whether or not the user recommendation output was completed, as determined from subsequent sensor data.

Abstract: The present disclosure relates automatically retrieving a workflow with an increased efficiency. The present disclosure further relates to detecting an intrusion in a distributed system, thereby improving system security. The present disclosure relates to a method for automatically retrieving a workflow, a device for automatically retrieving a workflow, a device for detecting an intrusion in a distributed system, and a storage medium for implementing a method according to the present disclosure.

Abstract: Various disclosed implementations involve processing and/or playback of a recording of a conference involving a plurality of conference participants. Some implementations disclosed herein involve analyzing conversational dynamics of the conference recording. Some examples may involve searching the conference recording to determine instances of segment classifications. The segment classifications may be based, at least in part, on conversational dynamics data. Some implementations may involve segmenting the conference recording into a plurality of segments, each of the segments corresponding with a time interval and at least one of the segment classifications. Some implementations allow a listener to scan through a conference recording quickly according to segments, words, topics and/or talkers of interest.

Abstract: A computer system is communicably coupled to one or more sensor devices. The computer system obtains a database of stored acoustic signatures characterizing predefined acoustic signals generated by passive tags in response to physical motion of respective monitored objects associated with the passive tags. A first acoustic signal characterized by a respective acoustic signature and generated by a first passive tag is detected. In response, and based on the respective acoustic signature and information in the database, a first monitored object associated with the respective acoustic signature is identified, and a first state of the first monitored object is determined. The determined first state is stored in the database, and an indication of the first state is provided to an associated monitoring service.

Abstract: A system, method, and apparatus for detecting drones are disclosed. An example method includes receiving a digital sound sample and partitioning the digital sound sample into segments. The method also includes applying a frequency and power spectral density transformation to each of the segments to produce respective sample vectors. For each of the sample vectors, the example method determines a combination of drone sound signatures and background sound signatures that most closely match the sample vector. The method further includes determining, for the sample vectors, if the drone sound signatures in relation to the background sound signatures that are included within the respective combinations are indicative of a drone. Conditioned on determining that the drone sound signatures are indicative of a drone, an alert message indicative of the drone is transmitted.

Abstract: A firearm mounted firing alert system for generating and transmitting alerts upon the discharge of a firearm to which it is attached. The firearm mounted firing alert system includes a device housing which includes an adhesive surface, a lighting element, a sensor set, a microcontroller, and a power source. The sensor set may embody a contact sensor for generating a contact alert whenever contact with the metallic surface of a firearm is lost, a vibration sensor for generating a vibration alert in response to a discharge vibration and a sound sensor for generating a sound alert in response to a discharge sound. Upon receiving these sensor alerts, the microcontroller transmits a notification over a networking interface to any device which has been preset to receive such notifications as well as cause the lighting element to illuminate.

Abstract: A band power computation device with which the amount of calculation required to compute channel power is reduced, and with which it is possible to obtain channel power with the same precision as when the channel power is obtained from the entire input signal. With this device, a subspace extraction unit (101) extracts a portion of the input signal. An FFT unit (104) performs a Fourier transformation on the extracted signal, generating a spectrum signal. A power computation unit (105) computes the channel power for each frequency from the spectrum signal. A power generation unit (150) expands the channel power to the same channel power as the channel power computed from the input signal, and smoothes the expanded channel power by performing a calculation sequentially from the highest frequency to the lowest frequency, said calculation using the expanded channel power and a prescribed constant.

Abstract: Buoyant sensor networks are described, comprising floating buoys with sensors and energy harvesting capabilities. The buoys can control their buoyancy and motion, and can organize communication in a distributed fashion. Some buoys may have tethered underwater vehicles with a smart spooling system that allows the vehicles to dive deep underwater while remaining in communication and connection with the buoys.

Abstract: A method for monitoring for seismic events by interrogating an optic fiber which forms part of an existing communications infrastructure to provide distributed acoustic sensing (DAS). The signals provided by the distributed sensing provide measurements at each of a plurality of discrete portions along the fiber, which may be many tens of kilometers in length. Warning or measurement and consequently prediction of seismic activity can be provided by collecting data over a wide area, without the need to deploy a correspondingly large fiber network.

Abstract: A method to control the operation of a wind turbine is provided. According to the method a sound of a bat in the area of the wind turbine is detected. According to the detected sound of the bat in the area of the wind turbine a parameter for the operation of the wind turbine is set.

Abstract: Aspects of this disclosure relate to protecting a circuit, such as an amplifier, from transient overdrive events and/or average overdrive events. In one embodiment, an indication of average power, such as root mean squared (RMS) power of a radio frequency (RF) signal, can be compared to a first threshold and an indication of a peak RF power can be compared to a second threshold. When the indication of average power exceeds the first threshold, an average overdrive event can be detected. When the indication of peak power exceeds the second threshold, a peak overdrive event can be detected. If either a transient overdrive event or an average overdrive event is detected, a circuit, such as an amplifier, can be protected.

Abstract: Conventionally, in order to obtain a difference signal between an A+N signal and an N signal and a difference signal between an A+B+N signal and the A+N signal, the A+N signal needs to be held in two different capacitors. Hence, there is a problem in that, due to variations in capacitance of the two capacitors, the difference signal between the A+N signal and the N signal and the difference signal between the A+B+N signal and the A+N signal may not accurately be obtained. An imaging device generates a signal obtained by subtracting the same digital N signal from each of the digital A+N signal and the digital A+B+N signal.

Abstract: Presented are systems and methods for deploying wireless data acquisition modules that facilitate autonomous initialization. The wireless data acquisition modules may initiate a initialization process in response to a stimulus associated with being deployed. The wireless data acquisition module may further conduct a neighbor discovery process and in turn establish a data transfer path among one or more other wireless data acquisition modules. Further, information obtained during a series of autonomous tests may be communicated during the neighbor discovery process and the establishment of the data transfer path may at least in part be based on the information obtained in the autonomous tests.

Abstract: A method of deterring mammals comprising configuring an acoustic deterrent system to emit an acoustic signal having characteristics which repel the mammals by eliciting an acoustic startle response reflex in said mammals.

Abstract: The present invention relates to a system and method for detecting bats from a remote location. In one aspect the invention provides a bat detection system comprising an upper detection unit connected to a base computer unit. The upper detection unit can be positioned on a vertical structure, and a second lower detection unit, or additional detection units, can also be positioned on the vertical structure. Each detection unit comprises a housing which is connected to, and contains, an audio detector. The base computer unit is enclosed by a housing and comprises a data processor, a data storage device, and a remote communication interface device. The data processor is operatively connected to the data storage device, remote communication interface device, and the audio detectors of any detection units positioned on the vertical structure. The base computer unit communicates with a remote computer transferring information regarding the bat sounds detected by the detection units.

Abstract: An acoustic object detector for detecting presence of an acoustic signal is provided. The acoustic object detector includes a number of bandpass filters. Each bandpass filter is configured to convert an input signal into an analog signal within a frequency band. The acoustic object detector also includes a number of spike generating circuits each coupled to the respective bandpass filter. Each spike generating circuit is configured to generate a series of spike signals based upon an adaptive threshold for the analog signal. The acoustic object detection further includes a decision circuit configured to generate a digital signal at a time-frequency point from the series of spike signals.

Abstract: A method (100) includes receiving (101) an input digital audio signal comprising a narrow-band signal. The input digital audio signal is processed (102) to generate a processed digital audio signal. A high-band energy level corresponding to the input digital audio signal is estimated (103) based on a transition-band of the processed digital audio signal within a predetermined upper frequency range of a narrow-band bandwidth. A high-band digital audio signal is generated (104) based on the high-band energy level and an estimated high-band spectrum corresponding to the high-band energy level.

Abstract: A system is provided for detecting the passage of vehicles and the classification thereof by weight using geophone outputs and a unique density measurement in which the number of peaks of the geophone signal above a predetermined threshold over a number of time frames indicates the presence of a vehicle, with the number of time frames in which the density exceeds the threshold indicating whether the vehicle is a heavy vehicle such as a tank, or a light vehicle such as a car, with the threshold eliminating both manmade and natural noise, as well as distinguishing seismic vibrations due to personnel and animals. In one embodiment, various thresholds are utilized to detect the onset of vehicle presence and the end of the event.

Abstract: The present invention relates to a system and method for detecting bats from a remote location. In one aspect the invention provides a bat detection system comprising an upper detection unit connected to a base computer unit. The upper detection unit can be positioned on a vertical structure, and a second lower detection unit, or additional detection units, can also be positioned on the vertical structure. Each detection unit comprises a housing which is connected to, and contains, an audio detector. The base computer unit is enclosed by a housing and comprises a data processor, a data storage device, and a remote communication interface device. The data processor is operatively connected to the data storage device, remote communication interface device, and the audio detectors of any detection units positioned on the vertical structure. The base computer unit communicates with a remote computer transferring information regarding the bat sounds detected by the detection units.

Abstract: A firearm equipped with a capability of wireless communication reports a discharge of the firearm to a reporting center terminal via a wireless communication link. The firearm includes a firearm housing including a trigger assembly. A sensor is coupled to the firearm housing for sensing the discharge of the firearm. The housing, e.g., portion of a pistol grip, also encases a wireless communication unit for transmitting a message indicating occurence of the firearm discharge to the terminal via wireless communication network. A GPS receiver installed in the firearm receives GPS signals from GPS satellites to enable calculation of the location of the firearm, either at the firearm or by a Position Determining Equipment (PDE), to identify the location of the firearm to the reporting center terminal. Upon detection of the discharge of the firearm, the firearm initiates activities of the GPS receiver and the wireless communication unit.

Abstract: A telemetry system is described in which a plurality of channels are coupled to a bus. A control subsystem controls the channels so that one of the channels presents to the bus during its designated time period a channel characteristic. The control subsystem interrogates in the analog domain each of the channels during its designated time period, and forms a signal representative of the channel characteristic. The control subsystem may combine one or more of the signals into a digital packet, and transmit the same via transceiver over a wireless network. The channels may be contained within a submersible enclosure and displaced at intervals along the bus, thereby forming an array for monitoring waterborne threats. The array may lie along an ocean floor, may be towed by a marine vehicle, or may suspended from a deployable buoy containing the control subsystem, transceiver, and a remote power source. The array may further comprise a defensive countermeasure deployable responsive to detecting a threat.

Abstract: A computer implemented method, program and system utilizing a number of field-deployed sensors to accurately detect and classify objects/events (targets) of interest within a sensor field including the detection/classification of human beings travelling on-foot or with vehicles and their direction(s) of travel. In particular, the method, computer program and system are operable to determine whether a detected target is an animal, human or vehicle via analysis of received acoustic and sensor data. The analyses performed include comparison/correlation of the sensor data to known seismic cyclostationary signatures, acoustic and seismic characteristics of human footsteps and travel tendencies, and acoustic and seismic characteristics of non-human (animal) footsteps and travel tendencies.

Abstract: The present invention relates to a system and method for detecting bats from a remote location. In one aspect the invention provides a bat detection system comprising an upper detection unit connected to a base computer unit. The upper detection unit can be positioned on a vertical structure, and a second lower detection unit, or additional detection units, can also be positioned on the vertical structure. Each detection unit comprises a housing which is connected to, and contains, an audio detector. The base computer unit is enclosed by a housing and comprises a data processor, a data storage device, and a remote communication interface device. The data processor is operatively connected to the data storage device, remote communication interface device, and the audio detectors of any detection units positioned on the vertical structure. The base computer unit communicates with a remote computer transferring information regarding the bat sounds detected by the detection units.

Abstract: The present disclosure relates to unattended ground sensors for detecting the presence of a pedestrian or vehicle in a monitored area using seismic sensors. Networks of simple and inexpensive sensors are disclosed that may be rapidly deployed. The networks may be formed from a dense array of low cost ground sensors having low sensitivity.

Abstract: In accordance with one aspect of the disclosed technology, wireless communications are used in a fiber surveillance system to enable monitoring of remote locations for vibrations, acoustic signals, stresses, stress fatigue or other detectable characteristics. A fiber that is deployed in the structure or region being monitored is connected a wireless transmitter that is used to transmit, to a receiving system, return optical signals obtained with the surveillance system. The return signals can be transmitted in raw form or after partial or total analysis.

Abstract: A signal analysis method extracts transient target signals of known type from a raw data source signal that contains an unknown number of target signals. The method can enhance the analysis of data obtained from in-line oil-debris sensors. The method comprises steps of: defining signatures of the known target signal, and of at least one of the intrinsic noise and interfering signals; performing a mathematical transform that decomposes the raw data into distinct data sets; using the signal signatures to identify and nullify the data sets containing noise and interfering signal signatures; using the target signal signatures to identify the data sets containing target signal components, or may further use a thresholding rule to remove intrinsic noise from said data sets, and finally applying the inverse transform to the processed data sets in order to reconstruct an enhanced output signal.

Abstract: The different advantageous embodiments provide a method and apparatus for detecting an aircraft. The different advantageous embodiments may provide a method for detecting an acoustic emission emitted by the aircraft using a number of acoustic sensors to form a detected acoustic emission. The aircraft may be identified from the detected acoustic emission to form an identified aircraft. A bearing may be estimated for the identified aircraft using the detected acoustic emission.

Abstract: A system for generating a threat alert in an infrastructure component is provided. The system includes multiple acoustic sensors configured to detect a signal. The system also includes a processing circuitry including at least one analog-to-digital converter configured to digitize the signal. The processing circuitry also includes a digital signal processor configured to process the acoustic signal in a sequential routine. The sequential routine includes a noise filtering routine configured to filter background noise from the acoustic signal and generate a filtered signal. The sequential routine also includes a source identification routine configured to identify a source generating the acoustic signal based upon the filtered signal. The sequential routine further includes a threat analysis routine configured to detect a threat based upon the source identified and generate a threat level signal.

Abstract: A method of event-based power management for seismic sensors is disclosed. The method comprises measuring seismic activity with a seismic sensor and comparing the measured seismic activity from the seismic sensor against at least one criteria. When the measured seismic activity does not satisfy the at least one criteria, a signal processing circuit is maintained in a deactivated state. When the measured seismic activity satisfies the at least one criteria, the signal processing circuit is activated to analyze the measured seismic activity. The signal processing circuit enters a functional mode based on analyzing the measured seismic activity.

Abstract: A system and method for implementing non-lethal chemical warfare against rampage shooters. A sound detection module detects a sound of a gunshot from at least one of a collection of sensors within a building. A sound location module determines a location of the gunshot by analyzing the sound. At least one emitter releases non-lethal chemical countermeasures from at least one at the location of the gunshot.

Abstract: Systems and methods for telescopic data compression in sensor networks are disclosed herein. An exemplary method of the disclosed subject matter for telescopically compressing data received from a plurality of sensors in a network adapted to detect a field includes broadcasting a first set of sampling positions to sensors, forming a first set of clusters of sensors based on the sampling positions, receiving data from the sensors contained within the clusters, performing local interpolation of the received data, reconstructing a representation of the field using the interpolated data, and determining areas of interest based on the reconstructed representation of the field.

Abstract: A method of detecting a human, that includes (a) measuring the ultrasonic signal emitted from human footsteps; (b) measuring the human body motion Doppler signature; reviewing the measurements of steps (a) and (b); and (d) determining the presence of a human.

Abstract: A method and apparatus for detecting an aircraft. The method is provided for wide area tracking of aircraft. An acoustic emission of the aircraft is detected from a plurality of locations. A position of the aircraft at a set of times is estimated by comparing a set of harmonically related Doppler shifted frequencies for the acoustic emission to an expected zero Doppler shifted frequency of the aircraft to form an estimated position. The position of the aircraft and a heading of the aircraft are tracked using the estimated position. The aircraft type is classified based on the corresponding set of zero Doppler frequencies at each acoustic sensor.

Abstract: An acoustic tone at a predetermined frequency is detected after being reflected and modulated by an unknown moving object. Acoustic features are extracted from the reflected acoustic tone using acoustic spectral analysis. A dimensionality of the acoustic features is reduced, and the reduced dimensionality features are statistically classified to identify the object.

Abstract: Disclosed herein is a fast method that locates nearby sources based solely on the time-of-flight of a signal across an array of sensors. The time delay for signal passage between all pairs of sensors is determined using cross-correlation estimates and a vector of time delays, ?, is constructed from the results. In the noise free case, each point in the plane is associated with a unique value of the ? vector. The plane is searched for a source location by minimizing the difference between the value of ? associated with the candidate location on the plane and the value estimated from cross-correlations. The search takes place over the three dimensional space that includes two coordinates in the plane and the propagation speed. The starting point for the search is constructed from an analytic fit of circular wave fronts to groups of sensors within the array.