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Filtering extracting features from infrasound data
University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
2006 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

 

The goal of the research presented in this thesis is to extract features, to filter and get fingerprints from signals detected by infrasound, seismic and magnetic sensors. If this can be achieved in a real time system, then signals from various events can be detected and identified in an otherwise torrent data.

Several approaches have been analyzed. Wavelet transform methods are used together with ampligram and time scale spectrum to analyze infrasound, seismic and magnetic data. The energy distribution in the frequency domain may be seen in wavelet scalograms. A scalogram displays the wavelet coefficients as a function of the time scale and of the elapsed time. The ampligram is a useful method of presentation of the physical properties of the time series. The ampligram demonstrate the amplitude and phase of components of the signal corresponding to different spectral densities. The ampligram may be considered as an analogy to signal decomposition into Fourier components. In that case different components correspond to different frequencies. In the present case different components correspond to different wavelet coefficient magnitudes, being equivalent to spectral densities. The time scale spectrum is a forward wavelet transform of each row (wavelet coefficient magnitude) in the ampligram. The time scale spectrum reveals individual signal components and indicates the statistical properties of each component: deterministic or stochastic.

Next step is to distinguish between different sources of infrasound on-line. This will require signal classification after detection is made. The implementation of wavelet – neural network in hardware may be a first choice. In this work the Independent Component Analysis is presented to improve the quality of the infrasonic signals by removing background noise before the hardware classification. The implementation of the discrete wavelet transform in a Field Programmable Gate Array (FPGA) is also included in this thesis using Xilinx System Generator and Simulink software.

A study of using infrasound recordings together with a miniature 3-axis fluxgate magnetometer to find meteorites as soon as possible after hitting the earth is also presented in this work.

Place, publisher, year, edition, pages
Stockholm: Kungliga Tekniska högskolan. Fysiska institutionen , 2006. , p. 48
Series
Trita-FYS, ISSN 0280-316X ; 2006:32
Keywords [en]
infrasound, seismic signals, feature extraction, wavelets, fingerprints, mining, magnetometer
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:hig:diva-3530OAI: oai:DiVA.org:hig-3530DiVA, id: diva2:134159
Presentation
2006-05-31, Sal FA32, AlbaNova, Roslagstullsbacken 21, Stockholm, 10:00 (English)
Opponent
Supervisors
Available from: 2009-01-20 Created: 2009-01-19 Last updated: 2018-03-13Bibliographically approved
List of papers
1. Infrasonic and Seismic Signals from Earthquake and Explosions in Arequipa, Perú
Open this publication in new window or tab >>Infrasonic and Seismic Signals from Earthquake and Explosions in Arequipa, Perú
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2006 (English)In: Western Pacific Geophysics Meeting., 2006Conference paper, Published paper (Other academic)
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:hig:diva-2380 (URN)
Conference
Western Pacific Geophysics Meeting. 24-27 July 2006, Beijing, China
Available from: 2007-03-02 Created: 2007-03-02 Last updated: 2018-03-13Bibliographically approved
2. Filtering and extracting features from infrasound data
Open this publication in new window or tab >>Filtering and extracting features from infrasound data
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2005 (English)In: Real Time Conference, 2005, 2005, p. 451-455Conference paper, Published paper (Refereed)
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:hig:diva-2379 (URN)10.1109/RTC.2005.1547494 (DOI)0-7803-9183-7 (ISBN)
Conference
14th IEEE-NPSS June 4-10 2005
Available from: 2007-03-02 Created: 2007-03-02 Last updated: 2018-03-13Bibliographically approved
3. Obtaining images from iron objects using a 3-axis fluxgate magnetometer
Open this publication in new window or tab >>Obtaining images from iron objects using a 3-axis fluxgate magnetometer
2006 (English)In: International Conference on Imaging Techniques in Subatomic Physics, Astrophysics, Medicine, Biology and Industry, 2006Conference paper, Published paper (Refereed)
Abstract [en]

Magnetic objects can cause local variations in the Earth's magnetic field that can be measured with a magnetometer. Here we used triaxial magnetometer measurements and an analysis method employing wavelet techniques to determine the "signature" or "fingerprint" of different iron objects. Clear distinctions among the iron samples were observed. The time-dependent changes in the frequency powers were extracted by use of the Morlet wavelet corresponding to frequency bands from 0.1 to 100 Hz. (c) 2007 Elsevier B.V. All rights reserved.

Keywords
magnetometer, feature extraction, wavelets, fingerprints
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:hig:diva-2381 (URN)10.1016/j.nima.2007.06.070 (DOI)000250128000058 ()
Conference
3rd International Conference on Imaging Techniques in Subatomic Physics, Astrophysics, Medicine, Biology and Industry, Stockholm, SWEDEN, JUN 27-30, 2006
Available from: 2007-03-02 Created: 2007-03-02 Last updated: 2018-03-13Bibliographically approved

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