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Ergodic theory. Information theory --- Mass communications --- Computer. Automation --- beeldverwerking --- coderen --- communicatietechnologie --- informatietheorie --- signaalverwerking
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Microphone arrays have attracted a lot of interest over the last few decades since they have the potential to solve many important problems such as noise reduction/speech enhancement, source separation, dereverberation, spatial sound recording, and source localization/tracking, to name a few. However, the design and implementation of microphone arrays with beamforming algorithms is not a trivial task when it comes to processing broadband signals such as speech. Indeed, in most sensor arrangements, the beamformer tends to have a frequency-dependent response. One exception, perhaps, is the family of differential microphone arrays (DMAs) that have the promise to form frequency-independent responses. Moreover, they have the potential to attain high directional gains with small and compact apertures. As a result, this type of microphone arrays has drawn much research and development attention recently. This book is intended to provide a systematic study of DMAs from a signal processing perspective. The primary objective is to develop a rigorous but yet simple theory for the design, implementation, and performance analysis of DMAs.
Vibrations --- Applied physical engineering --- Computer. Automation --- geluidsleer --- akoestiek --- beeldverwerking --- microfoons --- geluidsisolatie --- elektro-akoestiek --- ingenieurswetenschappen --- signaalverwerking
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Though noise reduction and speech enhancement problems have been studied for at least five decades, advances in our understanding and the development of reliable algorithms are more important than ever, as they support the design of tailored solutions for clearly defined applications. In this work, the authors propose a conceptual framework that can be applied to the many different aspects of noise reduction, offering a uniform approach to monaural and binaural noise reduction problems, in the time domain and in the frequency domain, and involving a single or multiple microphones. Moreover, the derivation of optimal filters is simplified, as are the performance measures used for their evaluation.
Electrical engineering --- Applied physical engineering --- Mass communications --- Computer. Automation --- DIP (documentimage processing) --- beeldverwerking --- spraaktechnologie --- elektrotechniek --- communicatietechnologie --- signaalverwerking
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Computer. Automation --- beeldverwerking --- informatica --- signaalverwerking
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Electronics --- Engineering sciences. Technology --- Mass communications --- Computer. Automation --- akoestiek --- beeldverwerking --- analyse (wiskunde) --- signal processing --- informatica --- elektronica --- ingenieurswetenschappen --- communicatietechnologie --- signaalverwerking
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Spectrometric and optical chemical analysis --- Computer. Automation --- beeldverwerking --- microfoons --- signal processing --- fysicochemie --- signaalverwerking --- spectrometrie
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This book provides a systematic study of the fundamental theory and methods of beamforming with differential microphone arrays (DMAs), or differential beamforming in short. It begins with a brief overview of differential beamforming and some popularly used DMA beampatterns such as the dipole, cardioid, hypercardioid, and supercardioid, before providing essential background knowledge on orthogonal functions and orthogonal polynomials, which form the basis of differential beamforming. From a physical perspective, a DMA of a given order is defined as an array that measures the differential acoustic pressure field of that order; such an array has a beampattern in the form of a polynomial whose degree is equal to the DMA order. Therefore, the fundamental and core problem of differential beamforming boils down to the design of beampatterns with orthogonal polynomials. But certain constraints also have to be considered so that the resulting beamformer does not seriously amplify the sensors’ self noise and the mismatches among sensors. Accordingly, the book subsequently revisits several performance criteria, which can be used to evaluate the performance of the derived differential beamformers. Next, differential beamforming is placed in a framework of optimization and linear system solving, and it is shown how different beampatterns can be designed with the help of this optimization framework. The book then presents several approaches to the design of differential beamformers with the maximum DMA order, with the control of the white noise gain, and with the control of both the frequency invariance of the beampattern and the white noise gain. Lastly, it elucidates a joint optimization method that can be used to derive differential beamformers that not only deliver nearly frequency-invariant beampatterns, but are also robust to sensors’ self noise.
Applied physical engineering --- Computer. Automation --- akoestiek --- beeldverwerking --- ingenieurswetenschappen --- signaalverwerking
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Recently, we proposed a completely novel and efficient way to design differential beamforming algorithms for linear microphone arrays. Thanks to this very flexible approach, any order of differential arrays can be designed. Moreover, they can be made robust against white noise amplification, which is the main inconvenience in these types of arrays. The other well-known problem with linear arrays is that electronic steering is not really feasible. In this book, we extend all these fundamental ideas to circular microphone arrays and show that we can design small and compact differential arrays of any order that can be electronically steered in many different directions and offer a good degree of control of the white noise amplification problem, high directional gain, and frequency-independent response. We also present a number of practical examples, demonstrating that differential beamforming with circular microphone arrays is likely one of the best candidates for applications involving speech enhancement (i.e., noise reduction and dereverberation). Nearly all of the material presented is new and will be of great interest to engineers, students, and researchers working with microphone arrays and their applications in all types of telecommunications, security and surveillance contexts.
Electrical engineering --- Applied physical engineering --- Mass communications --- Computer. Automation --- DIP (documentimage processing) --- beeldverwerking --- microfoons --- spraaktechnologie --- elektrotechniek --- communicatietechnologie --- signaalverwerking
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This book studies the link between differential beamforming and differential equations which in turn enables the study of fundamental theory and methods of beamforming from a different perspective, leading to new insights into the problem and new methods to solve the problem. The book first presents a brief overview of the problems and methods for beamforming and some performance measures popularly used either to evaluate beamformers or to derive optimal beamformers. Then, first-order, second-order, and general high-order linear difference equations are discussed, based on which the authors show how to formulate the beamforming problem and derive different beamforming methods, including fixed and adaptive ones. Furthermore, the authors show how to apply the theory of difference equations to the general problem of speech enhancement, and deduce a number of noise reduction filters, including the maximum SNR filter, the Wiener filter, the MVDR filter, etc. Also covered in the book are the difference equations and differential beamforming from the spectral graph perspective. Presents basic concepts, fundamental principles, and methods for beamforming from the perspective of linear difference equations; Provides formulation and methods of conventional beamforming, and first-order, second-order, and general high-order linear difference equations for beamforming; Includes the applications of linear difference equations to the problem of noise reduction; Explains beamforming based on difference equations with graphs.
Ergodic theory. Information theory --- Mathematical control systems --- Electronics --- Telecommunication technology --- Mass communications --- Computer. Automation --- coderen --- signal processing --- tekstverwerking --- signaalprocessoren --- communicatietechnologie --- informatietheorie --- signaalverwerking
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Vibrations --- Computer. Automation --- geluidsleer --- akoestiek --- beeldverwerking --- informatica --- signaalverwerking
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