Author: Charles J. Ammon
Publisher: Academic Press
ISBN: 0128165170
Category : Science
Languages : en
Pages : 606
Book Description
Modern Global Seismology, Second Edition, is a complete, self-contained primer on seismology, featuring extensive coverage of all related aspects—from observational data through prediction—and emphasizing the fundamental theories and physics governing seismic waves, both natural and anthropogenic. Based on thoroughly class-tested material, the text provides a unique perspective on Earth's large-scale internal structure and dynamic processes, particularly earthquake sources, and the application of theory to the dynamic processes of the earth's upper layer. This insightful new edition is designed for accessibility and comprehension for graduate students entering the field.Exploration seismologists will also find it an invaluable resource on topics such as elastic-wave propagation, seismic instrumentation, and seismogram analysis. - Includes more than 400 illustrations, from both recent and traditional research articles, to help readers visualize mathematical relationships, as well as boxed features to explain advanced topics - Offers incisive treatments of seismic waves, waveform evaluation and modeling, and seismotectonics, as well as quantitative treatments of earthquake source mechanics and numerous examples of modern broadband seismic recordings - Covers current seismic instruments and networks and demonstrates modern waveform inversion methods - Includes extensive, updated references for further reading new to this edition - Features reorganized chapters split into two sections, beginning with introductory content such as tectonics and seismogram analysis, and moving on to more advanced topics, including seismic wave excitation and propagation, multivariable and vector calculus, and tensor approaches - Completely updated references and figures to bring the text up to date Includes all-new sections on recent advancements and to enhance examples and understanding Split into shorter chapters to allow more flexibility for instructors and easier access for researchers, and includes exercises
Foundations of Modern Global Seismology
Author: Charles J. Ammon
Publisher: Academic Press
ISBN: 0128165170
Category : Science
Languages : en
Pages : 606
Book Description
Modern Global Seismology, Second Edition, is a complete, self-contained primer on seismology, featuring extensive coverage of all related aspects—from observational data through prediction—and emphasizing the fundamental theories and physics governing seismic waves, both natural and anthropogenic. Based on thoroughly class-tested material, the text provides a unique perspective on Earth's large-scale internal structure and dynamic processes, particularly earthquake sources, and the application of theory to the dynamic processes of the earth's upper layer. This insightful new edition is designed for accessibility and comprehension for graduate students entering the field.Exploration seismologists will also find it an invaluable resource on topics such as elastic-wave propagation, seismic instrumentation, and seismogram analysis. - Includes more than 400 illustrations, from both recent and traditional research articles, to help readers visualize mathematical relationships, as well as boxed features to explain advanced topics - Offers incisive treatments of seismic waves, waveform evaluation and modeling, and seismotectonics, as well as quantitative treatments of earthquake source mechanics and numerous examples of modern broadband seismic recordings - Covers current seismic instruments and networks and demonstrates modern waveform inversion methods - Includes extensive, updated references for further reading new to this edition - Features reorganized chapters split into two sections, beginning with introductory content such as tectonics and seismogram analysis, and moving on to more advanced topics, including seismic wave excitation and propagation, multivariable and vector calculus, and tensor approaches - Completely updated references and figures to bring the text up to date Includes all-new sections on recent advancements and to enhance examples and understanding Split into shorter chapters to allow more flexibility for instructors and easier access for researchers, and includes exercises
Publisher: Academic Press
ISBN: 0128165170
Category : Science
Languages : en
Pages : 606
Book Description
Modern Global Seismology, Second Edition, is a complete, self-contained primer on seismology, featuring extensive coverage of all related aspects—from observational data through prediction—and emphasizing the fundamental theories and physics governing seismic waves, both natural and anthropogenic. Based on thoroughly class-tested material, the text provides a unique perspective on Earth's large-scale internal structure and dynamic processes, particularly earthquake sources, and the application of theory to the dynamic processes of the earth's upper layer. This insightful new edition is designed for accessibility and comprehension for graduate students entering the field.Exploration seismologists will also find it an invaluable resource on topics such as elastic-wave propagation, seismic instrumentation, and seismogram analysis. - Includes more than 400 illustrations, from both recent and traditional research articles, to help readers visualize mathematical relationships, as well as boxed features to explain advanced topics - Offers incisive treatments of seismic waves, waveform evaluation and modeling, and seismotectonics, as well as quantitative treatments of earthquake source mechanics and numerous examples of modern broadband seismic recordings - Covers current seismic instruments and networks and demonstrates modern waveform inversion methods - Includes extensive, updated references for further reading new to this edition - Features reorganized chapters split into two sections, beginning with introductory content such as tectonics and seismogram analysis, and moving on to more advanced topics, including seismic wave excitation and propagation, multivariable and vector calculus, and tensor approaches - Completely updated references and figures to bring the text up to date Includes all-new sections on recent advancements and to enhance examples and understanding Split into shorter chapters to allow more flexibility for instructors and easier access for researchers, and includes exercises
Modern Global Seismology
Author: Thorne Lay
Publisher: Elsevier
ISBN: 0080536719
Category : Science
Languages : en
Pages : 535
Book Description
Intended as an introduction to the field, Modern Global Seismology is a complete, self-contained primer on seismology. It features extensive coverage of all related aspects, from observational data through prediction, emphasizing the fundamental theories and physics governing seismic waves--both natural and anthropogenic. Based on thoroughly class-tested material, the text provides a unique perspective on the earths large-scale internal structure and dynamic processes, particularly earthquake sources, and on the application of theory to the dynamic processes of the earths upper skin. Authored by two experts in the field of geophysics. this insightful text is designed for the first-year graduate course in seismology. Exploration seismologists will also find it an invaluable resource on topics such as elastic-wave propagation, seismicinstrumentation, and seismogram analysis useful in interpreting their high-resolution images of structure for oil and mineral resource exploration. - More than 400 illustrations, many from recent research articles, help readers visualize mathematical relationships - 49 Boxed Features explain advanced topics - Provides readers with the most in-depth presentation of earthquake physics available - Contains incisive treatments of seismic waves, waveform evaluation and modeling, and seismotectonics - Provides quantitative treatment of earthquake source mechanics - Contains numerous examples of modern broadband seismic recordings - Fully covers current seismic instruments and networks - Demonstrates modern waveform inversion methods - Includes extensive references for further reading
Publisher: Elsevier
ISBN: 0080536719
Category : Science
Languages : en
Pages : 535
Book Description
Intended as an introduction to the field, Modern Global Seismology is a complete, self-contained primer on seismology. It features extensive coverage of all related aspects, from observational data through prediction, emphasizing the fundamental theories and physics governing seismic waves--both natural and anthropogenic. Based on thoroughly class-tested material, the text provides a unique perspective on the earths large-scale internal structure and dynamic processes, particularly earthquake sources, and on the application of theory to the dynamic processes of the earths upper skin. Authored by two experts in the field of geophysics. this insightful text is designed for the first-year graduate course in seismology. Exploration seismologists will also find it an invaluable resource on topics such as elastic-wave propagation, seismicinstrumentation, and seismogram analysis useful in interpreting their high-resolution images of structure for oil and mineral resource exploration. - More than 400 illustrations, many from recent research articles, help readers visualize mathematical relationships - 49 Boxed Features explain advanced topics - Provides readers with the most in-depth presentation of earthquake physics available - Contains incisive treatments of seismic waves, waveform evaluation and modeling, and seismotectonics - Provides quantitative treatment of earthquake source mechanics - Contains numerous examples of modern broadband seismic recordings - Fully covers current seismic instruments and networks - Demonstrates modern waveform inversion methods - Includes extensive references for further reading
Elements of 3D Seismology, third edition
Author: Christopher L. Liner
Publisher: SEG Books
ISBN: 1560803371
Category : Science
Languages : en
Pages : 363
Book Description
Elements of 3D Seismology, third edition is a thorough introduction to the acquisition, processing, and interpretation of 3D seismic data. This third edition is a major update of the second edition. Sections dealing with interpretation have been greatly revised in accordance with improved understanding and availability of data and software. Practice exercises have been added, as well as a 3D seismic survey predesign exercise. Discussions include: conceptual and historical foundations of modern reflection seismology; an overview of seismic wave phenomena in acoustic, elastic, and porous media; acquisition principles for land and marine seismic surveys; methods used to create 2D and 3D seismic images from field data; concepts of dip moveout, prestack migration, and depth migration; concepts and limitations of 3D seismic interpretation for structure, stratigraphy, and rock property estimation; and the interpretation role of attributes, impedance estimation, and AVO. This book is intended as a general text on reflection seismology, including wave propagation, data acquisition, processing, and interpretation and will be of interest to entry-level geophysicists, experts in related fields (geology, petroleum engineering), and experienced geophysicists in one subfield wishing to learn about another (e.g., interpreters wanting to learn about seismic waves or data acquisition).
Publisher: SEG Books
ISBN: 1560803371
Category : Science
Languages : en
Pages : 363
Book Description
Elements of 3D Seismology, third edition is a thorough introduction to the acquisition, processing, and interpretation of 3D seismic data. This third edition is a major update of the second edition. Sections dealing with interpretation have been greatly revised in accordance with improved understanding and availability of data and software. Practice exercises have been added, as well as a 3D seismic survey predesign exercise. Discussions include: conceptual and historical foundations of modern reflection seismology; an overview of seismic wave phenomena in acoustic, elastic, and porous media; acquisition principles for land and marine seismic surveys; methods used to create 2D and 3D seismic images from field data; concepts of dip moveout, prestack migration, and depth migration; concepts and limitations of 3D seismic interpretation for structure, stratigraphy, and rock property estimation; and the interpretation role of attributes, impedance estimation, and AVO. This book is intended as a general text on reflection seismology, including wave propagation, data acquisition, processing, and interpretation and will be of interest to entry-level geophysicists, experts in related fields (geology, petroleum engineering), and experienced geophysicists in one subfield wishing to learn about another (e.g., interpreters wanting to learn about seismic waves or data acquisition).
Instrumentation in Earthquake Seismology
Author: Jens Havskov
Publisher: Springer Science & Business Media
ISBN: 1402029691
Category : Science
Languages : en
Pages : 365
Book Description
Here is unique and comprehensive coverage of modern seismic instrumentation, based on the authors’ practical experience of a quarter-century in seismology and geophysics. Their goal is to provide not only detailed information on the basics of seismic instruments but also to survey equipment on the market, blending this with only the amount of theory needed to understand the basic principles. Seismologists and technicians working with seismological instruments will find here the answers to their practical problems. Instrumentation in Earthquake Seismology is written to be understandable to the broad range of professionals working with seismological instruments and seismic data, whether students, engineers or seismologists. Whether installing seismic stations, networks and arrays, working and calibrating stationary or portable instruments, dealing with response information, or teaching about seismic instruments, professionals and academics now have a practical and authoritative sourcebook. Includes: SEISAN and SEISLOG software systems that are available from http://extras.springer.com and http://www.geo.uib.no/seismo/software/software.html
Publisher: Springer Science & Business Media
ISBN: 1402029691
Category : Science
Languages : en
Pages : 365
Book Description
Here is unique and comprehensive coverage of modern seismic instrumentation, based on the authors’ practical experience of a quarter-century in seismology and geophysics. Their goal is to provide not only detailed information on the basics of seismic instruments but also to survey equipment on the market, blending this with only the amount of theory needed to understand the basic principles. Seismologists and technicians working with seismological instruments will find here the answers to their practical problems. Instrumentation in Earthquake Seismology is written to be understandable to the broad range of professionals working with seismological instruments and seismic data, whether students, engineers or seismologists. Whether installing seismic stations, networks and arrays, working and calibrating stationary or portable instruments, dealing with response information, or teaching about seismic instruments, professionals and academics now have a practical and authoritative sourcebook. Includes: SEISAN and SEISLOG software systems that are available from http://extras.springer.com and http://www.geo.uib.no/seismo/software/software.html
International Handbook of Earthquake & Engineering Seismology, Part A
Author: William H.K. Lee
Publisher: Elsevier
ISBN: 0080489222
Category : Science
Languages : en
Pages : 994
Book Description
Modern scientific investigations of earthquakes began in the 1880s, and the International Association of Seismology was organized in 1901 to promote collaboration of scientists and engineers in studying earthquakes. The International Handbook of Earthquake and Engineering Seismology, under the auspices of the International Association of Seismology and Physics of the Earth's Interior (IASPEI), was prepared by leading experts under a distinguished international advisory board and team of editors.The content is organized into 56 chapters and includes over 430 figures, 24 of which are in color. This large-format, comprehensive reference summarizes well-established facts, reviews relevant theories, surveys useful methods and techniques, and documents and archives basic seismic data. It will be the authoritative reference for scientists and engineers and a quick and handy reference for seismologists.Also available is The International Handbook of Earthquake and Engineering Seismology, Part B.
Publisher: Elsevier
ISBN: 0080489222
Category : Science
Languages : en
Pages : 994
Book Description
Modern scientific investigations of earthquakes began in the 1880s, and the International Association of Seismology was organized in 1901 to promote collaboration of scientists and engineers in studying earthquakes. The International Handbook of Earthquake and Engineering Seismology, under the auspices of the International Association of Seismology and Physics of the Earth's Interior (IASPEI), was prepared by leading experts under a distinguished international advisory board and team of editors.The content is organized into 56 chapters and includes over 430 figures, 24 of which are in color. This large-format, comprehensive reference summarizes well-established facts, reviews relevant theories, surveys useful methods and techniques, and documents and archives basic seismic data. It will be the authoritative reference for scientists and engineers and a quick and handy reference for seismologists.Also available is The International Handbook of Earthquake and Engineering Seismology, Part B.
The East African Rift System
Author: Athanas Simon Macheyeki
Publisher: Elsevier
ISBN: 0323956432
Category : Technology & Engineering
Languages : en
Pages : 366
Book Description
The East African Rift System: Geodynamics and Natural Resource Potentials provides state-of-the-art knowledge and skills on how to explore, model, and extract the resources, using the East African Rift System (EARS) as a model. Each aspect to be discussed in the East African Rift System shall have its equivalent case study and readers interested in each rift of the world will find something connected or linked to his/her rift system of interest, be it a sub-chapter on earthquakes, geothermal energy models, etc. The East African Rift System: Geodynamics and Natural Resource Potentials also describes rifting models of all other known rifts (especially continental rifts) of the world such as the Basin and Range Province, Rio Grande (USA); Rhine Graben (France and Germany); the Tibetan Rohai (Tibet); the Shaanxi Bohai (China); Lake Baikal (Russia); North Island (Australia); and the Aegean Sea Rift (Turkey). Key aspects to be presented shall be: rift type, rift age, rift physical dimensions, geothermal gradient models, natural resources, and models of exploration. - Connects the science of rift systems to their economic potentials using the East African Rift System as the prime example - Includes discussions and case studies from rift systems around the world - Features chapters dedicated to natural resources, such as mineral deposit types (Au, He, REE, U) and the basic principles of their exploration?
Publisher: Elsevier
ISBN: 0323956432
Category : Technology & Engineering
Languages : en
Pages : 366
Book Description
The East African Rift System: Geodynamics and Natural Resource Potentials provides state-of-the-art knowledge and skills on how to explore, model, and extract the resources, using the East African Rift System (EARS) as a model. Each aspect to be discussed in the East African Rift System shall have its equivalent case study and readers interested in each rift of the world will find something connected or linked to his/her rift system of interest, be it a sub-chapter on earthquakes, geothermal energy models, etc. The East African Rift System: Geodynamics and Natural Resource Potentials also describes rifting models of all other known rifts (especially continental rifts) of the world such as the Basin and Range Province, Rio Grande (USA); Rhine Graben (France and Germany); the Tibetan Rohai (Tibet); the Shaanxi Bohai (China); Lake Baikal (Russia); North Island (Australia); and the Aegean Sea Rift (Turkey). Key aspects to be presented shall be: rift type, rift age, rift physical dimensions, geothermal gradient models, natural resources, and models of exploration. - Connects the science of rift systems to their economic potentials using the East African Rift System as the prime example - Includes discussions and case studies from rift systems around the world - Features chapters dedicated to natural resources, such as mineral deposit types (Au, He, REE, U) and the basic principles of their exploration?
Geophysics
Author: William Lowrie
Publisher: Oxford University Press
ISBN: 0198792956
Category : Mathematics
Languages : en
Pages : 161
Book Description
1. What is geophysics? -- 2. Planet Earth -- 3. Seismology and the Earth's internal structure -- 4. Siesmicity--the restless Earth -- 5. Gravity and the figure of the Earth -- 6. The Earth's heat -- 7. The Earth's magnetic field -- 8. Afterthoughts
Publisher: Oxford University Press
ISBN: 0198792956
Category : Mathematics
Languages : en
Pages : 161
Book Description
1. What is geophysics? -- 2. Planet Earth -- 3. Seismology and the Earth's internal structure -- 4. Siesmicity--the restless Earth -- 5. Gravity and the figure of the Earth -- 6. The Earth's heat -- 7. The Earth's magnetic field -- 8. Afterthoughts
Computational Seismology
Author: Heiner Igel
Publisher: Oxford University Press
ISBN: 0198717407
Category : Nature
Languages : en
Pages : 340
Book Description
An introductory text to a range of numerical methods used today to simulate time-dependent processes in Earth science, physics, engineering and many other fields. It looks under the hood of current simulation technology and provides guidelines on what to look out for when carrying out sophisticated simulation tasks.
Publisher: Oxford University Press
ISBN: 0198717407
Category : Nature
Languages : en
Pages : 340
Book Description
An introductory text to a range of numerical methods used today to simulate time-dependent processes in Earth science, physics, engineering and many other fields. It looks under the hood of current simulation technology and provides guidelines on what to look out for when carrying out sophisticated simulation tasks.
Predicting the Unpredictable
Author: Susan Elizabeth Hough
Publisher: Princeton University Press
ISBN: 0691173303
Category : Science
Languages : en
Pages : 276
Book Description
Why seismologists still can't predict earthquakes An earthquake can strike without warning and wreak horrific destruction and death, whether it's the catastrophic 2010 quake that took a devastating toll on the island nation of Haiti or a future great earthquake on the San Andreas Fault in California, which scientists know is inevitable. Yet despite rapid advances in earthquake science, seismologists still can’t predict when the Big One will hit. Predicting the Unpredictable explains why, exploring the fact and fiction behind the science—and pseudoscience—of earthquake prediction. Susan Hough traces the continuing quest by seismologists to forecast the time, location, and magnitude of future quakes. She brings readers into the laboratory and out into the field—describing attempts that have raised hopes only to collapse under scrutiny, as well as approaches that seem to hold future promise. She also ventures to the fringes of pseudoscience to consider ideas outside the scientific mainstream. An entertaining and accessible foray into the world of earthquake prediction, Predicting the Unpredictable illuminates the unique challenges of predicting earthquakes.
Publisher: Princeton University Press
ISBN: 0691173303
Category : Science
Languages : en
Pages : 276
Book Description
Why seismologists still can't predict earthquakes An earthquake can strike without warning and wreak horrific destruction and death, whether it's the catastrophic 2010 quake that took a devastating toll on the island nation of Haiti or a future great earthquake on the San Andreas Fault in California, which scientists know is inevitable. Yet despite rapid advances in earthquake science, seismologists still can’t predict when the Big One will hit. Predicting the Unpredictable explains why, exploring the fact and fiction behind the science—and pseudoscience—of earthquake prediction. Susan Hough traces the continuing quest by seismologists to forecast the time, location, and magnitude of future quakes. She brings readers into the laboratory and out into the field—describing attempts that have raised hopes only to collapse under scrutiny, as well as approaches that seem to hold future promise. She also ventures to the fringes of pseudoscience to consider ideas outside the scientific mainstream. An entertaining and accessible foray into the world of earthquake prediction, Predicting the Unpredictable illuminates the unique challenges of predicting earthquakes.
Direction of Arrival Estimation for Wildlife Protection
Author: Gustav Zetterqvist
Publisher: Linköping University Electronic Press
ISBN: 9180758304
Category :
Languages : en
Pages : 93
Book Description
Direction of arrival (DOA) estimation is a well-established problem in signal processing. It involves determining the direction from which a signal reaches a sensor array, and is fundamental in applications like radar, sonar, and acoustics. Traditionally, DOA estimation relies on comparing the time of arrival of the signal across different sensors in the array. However, this approach is sensitive to the time difference of arrival (TDOA) between sensors, which can be challenging to estimate accurately. Additionally, precise synchronization among the sensors is essential, but this can be difficult to achieve in certain environments or applications. In this thesis, we explore a novel approach to DOA estimation based on the received signal power at the sensors. The method exploits the directional sensitivity of the microphones in the array, which defines how effectively each microphone captures sound from different directions. To model the directional sensitivity, we use a Fourier series (FS) model. The model is then used to estimate the DOA of a sound source across various environments, and for different types of signals. The parametric model enables Cramér-Rao lower bound (CRLB) analysis of the DOA estimation problem. Our findings demonstrate that the directional sensitivity exhibits a significant variation in accordance with the frequency content of the signal, and we exploit this to estimate the DOA for different types of sounds. The proposed method has been validated with a range of signals, including gunshots, elephant trumpets, sirens, and female screams. The results show that the developed method achieves high accuracy in estimating the DOA for the above-mentioned signals. Furthermore, the method performs similarly well in outdoor scenarios with realistic background noise levels. When compared to state-of-the-art DOA estimation techniques, our approach performs better or equally well for the investigated sounds. A key advantage of this method is that it does not require any TDOA measurement between the microphones, enabling the design of smaller, more compact devices. This opens up new possibilities for estimating DOA in environments where traditional methods are impractical. A limitation, however, is that the method requires knowledge of the microphone’s directional sensitivity, which necessitates calibration in an anechoic chamber. Nevertheless, this calibration has proven to be robust, and only needs to be performed once to create a model applicable across different environments. Additionally, this thesis explores a different application of DOA estimation, where geophones are used to estimate the DOA to elephants. As elephants move, they generate ground vibrations, and these signals can be captured by geophones. We show that a traditional delay-and-sum beamformer can accurately estimate the DOA of elephants at distances up to 40 meters. By determining when elephants are approaching and from which direction, park rangers can take early measures to avoid conflicts between humans and elephants, which is a major problem in some parts of the world. Förmågan att höra var ett ljud kommer ifrån, något vi ofta tar för givet, kallas för riktningsuppfattning. Den gör det möjligt för oss att snabbt avgöra om någon ropar på oss och från vilket håll ljudet kommer. Denna förmåga är viktig för att kunna orientera sig i omgivningen och uppfatta hot eller andra viktiga ljud. Våra öron samarbetar genom att jämföra hur ljud når varje öra, både när det gäller ljudets intensitet och hur lång tid det tar för ljudet att nå dem. Det här kallas för interaural tids- och nivåskillnad. Vissa ljud kan dock vara svåra att uppfatta, till exempel om ljudet är kort och impulsivt, eller om det är i en stadsmiljö med mycket bakgrundsljud och reflektioner. I den här avhandlingen undersöker vi nya metoder för att uppskatta ljudets riktning. Vi använder mikrofoner för att mäta ljudet och beräknar därefter riktningen som ljudet kommer ifrån. Traditionella metoder fokuserar på tidsskillnaden mellan ljud som registreras i olika mikrofoner. Vi tar istället en annan väg och undersöker hur ljudets styrka kan användas för att avgöra riktningen, oavsett tidsskillnader mellan mikrofonerna. Vår metod bygger på att vi skapar en modell av mikrofonernas riktningskänslighet, det vill säga hur väl de uppfattar ljud från olika håll. Modellen skapas genom att mäta mikrofonens riktningskänslighet i ett ekofritt rum. Genom att först mäta detta i en kontrollerad miljö, utan ekon, kan vi sedan använda modellen för att beräkna ljudriktningen i mer varierande miljöer och för olika typer av ljud. Till exempel har vi använt ljud såsom pistolskott, elefanttrumpeter, sirener och skrik för att testa vår metod. Resultaten visar att vår metod kan beräkna riktningar med hög noggrannhet för de ovan nämnda ljuden, även i en utomhusmiljö med mer realistiska nivåer av bakgrundsljud. När vi jämfört vår metod med traditionella metoder, presterar vår lösning lika bra eller bättre för de testade ljuden. En stor fördel med vår metod är att den inte kräver att mikrofonerna är placerade på ett visst avstånd från varandra, vilket innebär att vi kan bygga mindre och mer kompakta enheter. Detta kan leda till nya typer av produkter för att identifiera ljudriktningar i olika situationer. En nackdel är dock att mikrofonernas riktningskänslighet måste kalibreras i ett ljudlabb, men denna kalibrering har visat sig vara robust och det räcker att utföra en kalibrering som kan användas i flera olika miljöer. I avhandlingen inkluderas även en annan tillämpning av riktningsskattning, nämligen att uppskatta riktningen till elefanter med hjälp av geofoner som mäter vibrationer i marken. Elefanter är stora djur som skapar tydliga vibrationer i marken när de går. Genom att mäta dessa vibrationer med geofoner kan vi uppskatta riktningen till elefanten. Vi visar att traditionella metoder kan uppskatta riktningen med hög noggrannhet på ett avstånd upp till 40 meter. Genom att avgöra när elefanter närmar sig människor och varifrån de kommer kan parkvakter vidta åtgärder för att undvika konflikter mellan människor och elefanter, vilket är ett stort problem i vissa delar av världen.
Publisher: Linköping University Electronic Press
ISBN: 9180758304
Category :
Languages : en
Pages : 93
Book Description
Direction of arrival (DOA) estimation is a well-established problem in signal processing. It involves determining the direction from which a signal reaches a sensor array, and is fundamental in applications like radar, sonar, and acoustics. Traditionally, DOA estimation relies on comparing the time of arrival of the signal across different sensors in the array. However, this approach is sensitive to the time difference of arrival (TDOA) between sensors, which can be challenging to estimate accurately. Additionally, precise synchronization among the sensors is essential, but this can be difficult to achieve in certain environments or applications. In this thesis, we explore a novel approach to DOA estimation based on the received signal power at the sensors. The method exploits the directional sensitivity of the microphones in the array, which defines how effectively each microphone captures sound from different directions. To model the directional sensitivity, we use a Fourier series (FS) model. The model is then used to estimate the DOA of a sound source across various environments, and for different types of signals. The parametric model enables Cramér-Rao lower bound (CRLB) analysis of the DOA estimation problem. Our findings demonstrate that the directional sensitivity exhibits a significant variation in accordance with the frequency content of the signal, and we exploit this to estimate the DOA for different types of sounds. The proposed method has been validated with a range of signals, including gunshots, elephant trumpets, sirens, and female screams. The results show that the developed method achieves high accuracy in estimating the DOA for the above-mentioned signals. Furthermore, the method performs similarly well in outdoor scenarios with realistic background noise levels. When compared to state-of-the-art DOA estimation techniques, our approach performs better or equally well for the investigated sounds. A key advantage of this method is that it does not require any TDOA measurement between the microphones, enabling the design of smaller, more compact devices. This opens up new possibilities for estimating DOA in environments where traditional methods are impractical. A limitation, however, is that the method requires knowledge of the microphone’s directional sensitivity, which necessitates calibration in an anechoic chamber. Nevertheless, this calibration has proven to be robust, and only needs to be performed once to create a model applicable across different environments. Additionally, this thesis explores a different application of DOA estimation, where geophones are used to estimate the DOA to elephants. As elephants move, they generate ground vibrations, and these signals can be captured by geophones. We show that a traditional delay-and-sum beamformer can accurately estimate the DOA of elephants at distances up to 40 meters. By determining when elephants are approaching and from which direction, park rangers can take early measures to avoid conflicts between humans and elephants, which is a major problem in some parts of the world. Förmågan att höra var ett ljud kommer ifrån, något vi ofta tar för givet, kallas för riktningsuppfattning. Den gör det möjligt för oss att snabbt avgöra om någon ropar på oss och från vilket håll ljudet kommer. Denna förmåga är viktig för att kunna orientera sig i omgivningen och uppfatta hot eller andra viktiga ljud. Våra öron samarbetar genom att jämföra hur ljud når varje öra, både när det gäller ljudets intensitet och hur lång tid det tar för ljudet att nå dem. Det här kallas för interaural tids- och nivåskillnad. Vissa ljud kan dock vara svåra att uppfatta, till exempel om ljudet är kort och impulsivt, eller om det är i en stadsmiljö med mycket bakgrundsljud och reflektioner. I den här avhandlingen undersöker vi nya metoder för att uppskatta ljudets riktning. Vi använder mikrofoner för att mäta ljudet och beräknar därefter riktningen som ljudet kommer ifrån. Traditionella metoder fokuserar på tidsskillnaden mellan ljud som registreras i olika mikrofoner. Vi tar istället en annan väg och undersöker hur ljudets styrka kan användas för att avgöra riktningen, oavsett tidsskillnader mellan mikrofonerna. Vår metod bygger på att vi skapar en modell av mikrofonernas riktningskänslighet, det vill säga hur väl de uppfattar ljud från olika håll. Modellen skapas genom att mäta mikrofonens riktningskänslighet i ett ekofritt rum. Genom att först mäta detta i en kontrollerad miljö, utan ekon, kan vi sedan använda modellen för att beräkna ljudriktningen i mer varierande miljöer och för olika typer av ljud. Till exempel har vi använt ljud såsom pistolskott, elefanttrumpeter, sirener och skrik för att testa vår metod. Resultaten visar att vår metod kan beräkna riktningar med hög noggrannhet för de ovan nämnda ljuden, även i en utomhusmiljö med mer realistiska nivåer av bakgrundsljud. När vi jämfört vår metod med traditionella metoder, presterar vår lösning lika bra eller bättre för de testade ljuden. En stor fördel med vår metod är att den inte kräver att mikrofonerna är placerade på ett visst avstånd från varandra, vilket innebär att vi kan bygga mindre och mer kompakta enheter. Detta kan leda till nya typer av produkter för att identifiera ljudriktningar i olika situationer. En nackdel är dock att mikrofonernas riktningskänslighet måste kalibreras i ett ljudlabb, men denna kalibrering har visat sig vara robust och det räcker att utföra en kalibrering som kan användas i flera olika miljöer. I avhandlingen inkluderas även en annan tillämpning av riktningsskattning, nämligen att uppskatta riktningen till elefanter med hjälp av geofoner som mäter vibrationer i marken. Elefanter är stora djur som skapar tydliga vibrationer i marken när de går. Genom att mäta dessa vibrationer med geofoner kan vi uppskatta riktningen till elefanten. Vi visar att traditionella metoder kan uppskatta riktningen med hög noggrannhet på ett avstånd upp till 40 meter. Genom att avgöra när elefanter närmar sig människor och varifrån de kommer kan parkvakter vidta åtgärder för att undvika konflikter mellan människor och elefanter, vilket är ett stort problem i vissa delar av världen.