Passive detection of low frequency sources using vector sensor channel cross correlation

2017 ◽  
Vol 141 (5) ◽  
pp. 3650-3650
Author(s):  
Thomas J. Deal
Keyword(s):  
Cross Correlation ◽  
Low Frequency ◽  
Passive Detection ◽  
Vector Sensor ◽  
Sensor Channel

scholarly journals LOW-FREQUENCY NOISE MEASUREMENTS OF IR PHOTODETECTORS WITH VOLTAGE CROSS CORRELATION SYSTEM

Measurement ◽  
2021 ◽  
pp. 109867
Author(s):  
Krzysztof ACHTENBERG ◽  
Janusz MIKOŁAJCZYK ◽  
Carmine CIOFI ◽  
Graziella SCANDURRA ◽  
Krystian MICHALCZEWSKI ◽  
...  
Keyword(s):  
Cross Correlation ◽  
Low Frequency ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Ir Photodetectors ◽  
Noise Measurements ◽  
Correlation System

Modelling the sensitivity of cells in the anteroventral cochlear nucleus to spatiotemporal discharge patterns

1992 ◽  
Vol 336 (1278) ◽  
pp. 403-406 ◽  
Keyword(s):  
Cochlear Nucleus ◽  
Auditory Nerve ◽  
Cross Correlation ◽  
Low Frequency ◽  
Phase Spectrum ◽  
Coincidence Detection ◽  
Potential Mechanism ◽  
Complex Sounds ◽  
Anteroventral Cochlear Nucleus ◽  
Discharge Patterns

This study investigates a potential mechanism for the processing of acoustic information that is encoded in the spatiotemporal discharge patterns of auditory nerve (AN) fibres. Recent physiological evidence has demonstrated that some low-frequency cells in the anteroventral cochlear nucleus (AVCN) are sensitive to manipulations of the phase spectrum of complex sounds (Carney 1990 b ). These manipulations result in systematic changes in the spatiotemporal discharge patterns across groups of low-frequency an fibres having different characteristic frequencies (CFS). One interpretation of these results is that these neurons in the AVCN receive convergent inputs from AN fibres with different CFS, and that the cells perform a coincidence detection or cross-correlation upon their inputs. This report presents a model that was developed to test this interpretation.

scholarly journals A Recursive Algorithm for Indoor Positioning Using Pulse-Echo Ultrasonic Signals

Sensors ◽  
2020 ◽  
Vol 20 (18) ◽  
pp. 5042
Author(s):  
Salvatore A. Pullano ◽  
Maria Giovanna Bianco ◽  
Davide C. Critello ◽  
Michele Menniti ◽  
Antonio La Gatta ◽  
...  
Keyword(s):  
Communication Systems ◽  
Polyvinylidene Fluoride ◽  
Cross Correlation ◽  
Recursive Algorithm ◽  
Low Frequency ◽  
Correlation Method ◽  
Experimental Results ◽  
Ultrasonic Signals ◽  
Average Improvement ◽  
Pulse Echo

Low frequency ultrasounds in air are widely used for real-time applications in short-range communication systems and environmental monitoring, in both structured and unstructured environments. One of the parameters widely evaluated in pulse-echo ultrasonic measurements is the time of flight (TOF), which can be evaluated with an increased accuracy and complexity by using different techniques. Hereafter, a nonstandard cross-correlation method is investigated for TOF estimations. The procedure, based on the use of template signals, was implemented to improve the accuracy of recursive TOF evaluations. Tests have been carried out through a couple of 60 kHz custom-designed polyvinylidene fluoride (PVDF) hemicylindrical ultrasonic transducers. The experimental results were then compared with the standard threshold and cross-correlation techniques for method validation and characterization. An average improvement of 30% and 19%, in terms of standard error (SE), was observed. Moreover, the experimental results evidenced an enhancement in repeatability of about 10% in the use of a recursive positioning system.

The research of passive detection parameter measurement based on vector sensor

2019 ◽  
Vol 145 (3) ◽  
pp. 1693-1693
Author(s):  
Juan Hui ◽  
Xianzhong Bu ◽  
Anbang Zhao ◽  
Dayu Wang ◽  
Jin Li
Keyword(s):  
Parameter Measurement ◽  
Passive Detection ◽  
Vector Sensor

scholarly journals Theoretical and experimental study on a finite size vector sensor array with a cylindrically symmetric carrier

2019 ◽  
Vol 283 ◽  
pp. 07008
Author(s):  
Junyuan Guo ◽  
Shi-e Yang ◽  
Hongjuan Chen ◽  
Shengchun Piao ◽  
Longhao Qiu
Keyword(s):  
Finite Size ◽  
Low Frequency ◽  
Doa Estimation ◽  
Radial Component ◽  
Tangential Component ◽  
Low Frequencies ◽  
Cylindrically Symmetric ◽  
Noise Characteristics ◽  
Vector Sensor ◽  
Array Gain

In this work, a finite size acoustic vector sensor (AVS) array is designed and its performance is theoretically and experimentally studied. The two-dimensional AVS array is comprised of five vector sensors and configured as a cross, and the array carrier is a cylindrically symmetric structure. Theoretical analysis and simulation indicate that the proposed method considering structure scattering can widen the working bandwidth. Furthermore, the utilization of vector sensor enables a significant white noise gain improvement at low frequencies, which makes the array more robust and easier to realize. Experiments have been done to study the array performance from several aspects including sensor noise characteristics, the beampattern, the direction-of-arrival (DOA) estimation ability and the array gain. From the change of the sensor directivity patterns or the amplitude distortion of the noise field, we can clearly observe the scattering field intensity. Moreover, it shows that the influence of the structure scattering on the tangential component of the vector field is symmetric, while that of the radial component is asymmetric. Experimental results also demonstrate that, with the proposed method, the 2nd and the 3rd order beamformers can be obtained which could be further used for the estimation of target DOA. In addition, an array gain of at least 6 dB is obtained capable of detection of weak signals. Our results indicate that the proposed array with a physical size less than one meter, although affected by nearby scatterers, can effectively break the Rayleigh limit and realize the remote detection in low-frequency regime.

scholarly journals WAVE GROUPINESS AS A SOURCE OF NEARSHORE LONG WAVES

1986 ◽  
Vol 1 (20) ◽  
pp. 38 ◽  
Author(s):  
Jeffrey H. List
Keyword(s):  
Wave Amplitude ◽  
Cross Correlation ◽  
Surf Zone ◽  
Low Frequency ◽  
Long Waves ◽  
Progressive Wave ◽  
Wave Groups ◽  
Long Wave ◽  
Cross Correlation Analysis ◽  
Limited Usefulness

Data from a low energy swell-dominated surf zone are examined for indications that observed low frequency motions are simply group-forced bounded long waves. Time series of wave amplitude are compared to filtered long wave records through cross-spectral and cross-correlation analysis. These methods are found to have limited usefulness until long waves are separated into seaward and shoreward components. Then a clear picture of a rapidly shoaling bounded long wave emerges, with a minimum of nearly one fourth of the long wave amplitude being explainable by this type of motion close to shore. Through the zone in which waves were breaking, and incident wave amplitude variability decreased by 50%, the contribution from the bounded long wave continued to increase at a rate much greater than a simple shoaling effect. Also present are clear signs that this amplified bounded long wave is reflected from a position close to the shoreline, and is thus released from wave groups as a free, offshore-progressive wave.

scholarly journals Improved earthquake detection as a probe for active fault structures in New Zealand's central Southern Alps

2021 ◽  
Author(s):  
◽  
Calum Chamberlain
Keyword(s):  
Cross Correlation ◽  
Matched Filter ◽  
Low Frequency ◽  
Southern Alps ◽  
Phase 2 ◽  
Earthquake Detection ◽  
Alpine Fault ◽  
Drill Site ◽  
Python Package ◽  
Drilling Project

<p>This thesis concerns the detection and analysis of micro-seismicity and low-frequency earthquakes in New Zealand's central Southern Alps. We make use of the 6.5 year continuous seismic dataset collected using the Southern Alps Microearthquake Borehole Array (SAMBA), alongside other temporary and permanent seismic deployments nearby. The small station spacing of this deployment allows for high resolution seismic studies near the Alpine Fault, a dextral-transpressive plate boundary fault between the Pacific and Australian plates.  Using this dataset we have documented the rst evidence of low-frequency earthquakes on or near the deep extent of the Alpine Fault. By using a network based crosscorrelation detection method we have generated a 3 year catalogue of 14 low-frequency earthquake families. These low-frequency earthquake families locate close to other indicators and models of the deep extent of the Alpine Fault, and we interpret these low-frequency earthquakes to represent shear failure on or near the deep extent of the Alpine Fault. These low-frequency earthquakes highlight a near-continuous background rate of deformation, punctuated by short periods of tremor. We also observe higher rates of low-frequency earthquake generation after large regional earthquakes. The magnitudes of our low-frequency earthquakes range from Mʟ‒0.8‒1.8, and appear to follow an exponential distribution, implying that there might be a characteristic length-scale of failure.  We have extended the catalogue of low-frequency earthquake templates using the full 6.5 year dataset and an objective synthetic detection methodology. We developed a new methodology for template detection after other methods failed, or were not feasible. This method employs simple synthetic template events, which, rather than trying to capture all of the complexities of the body waves we try to detect, approximate a simple waveform that does not correlate well with background noise. To undertake this method we have developed a multi-parallel Python package, which is highly portable (we have run this on computers ranging from dual-core, 8GB RAM laptops to a 393 node, 6349 CPU cluster computer) and distributed via an open-source model. This package was run through the 6.5 year dataset on the New Zealand E-Science PAN cluster to e fficiently (<48 hours clock-time) generate a spatially and temporally continuous catalogue of low-frequency earthquake templates. Using this method to detect an initial suite of over 25,000 detections grouped into 600 families we have generated 600 good quality, discrete stacked waveforms for use in further matched-filter detection routines. We have shown that, for templates with both P and S-phase picks, these templates locate near to our previously determined low-frequency earthquake family locations.  Using a network matched- filter detection technique we have generated a catalogue of micro-seismicity in a region of low-seismicity near the Whataroa Valley, motivated by the Deep-Fault Drilling Project; Phase-2. We detected 300 earthquakes that include a selection of near-repeating earthquakes. We find that most detected events are not similar enough to be termed repeating. For 106 earthquakes we are able to generate high-precision magnitudes calculated by singular-value decomposition of similar waveforms. We find a high b-value of 1.44 for these earthquakes, with no earthquakes above Mʟ1.6. By generating high precision cross-correlation derived picks for individual detections and employing a double-difference location methodology we show that seismicity does not delineate a single structure; rather we interpret the detected seismicity as temporally-limited earthquake sequences on small asperities adjacent to the Alpine Fault. Focal mechanisms for the best recorded events show dominantly strike-slip mechanisms, with lesser reverse and normal components.  During the drilling of the Deep-Fault Drilling Project: Phase-2 borehole we operated a real-time earthquake detection system around the drill-site. This was a multi-national effort involving 16 seismologists in three countries monitoring the automatic detections in shifts. During the 5 month real-time monitoring period we detected and located 493 earthquakes, none of which occurred within 3km of the drill-site, nor required changes to the drilling operations. We undertook this monitoring using open-source software, which employed a standard energy based detection scheme.  This thesis has contributed four complementary earthquake catalogues, a further three years of continuous seismic data from the central Southern Alps, and an opensource Python package for detection and analysis of earthquakes using cross-correlation techniques. The characteristics of these catalogues highlight deformation modes on and near one of the world's major strike-slip plate boundaries, both at depth, and at the upper extent of the seismogenic zone.</p>

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