Active Control Of Sound

This book describes modern techniques for reducing the level of airborne noise through the introduction of sound radiated by additional secondary sources, bringing together the results of contemporary research in this area. It is the combination of the physical properties of sound fields and modern digital signal processing technology that has made the active control of sound a practical proposition in a number of important applications. The book covers both these aspects of the subject, initially at a fundamental level, and then in detail in later chapters. The structure of the book is such that it should be suitable for both those seeking a basic understanding of the subject and as a reference for researchers in the field. A key feature of the work is the unified presentation of material from the two disciplines of acoustics and signal processing.

Integrating active control of both sound and vibration, this comprehensive two-volume set combines coverage of fundamental principles with the most recent theoretical and practical developments. The authors explain how to design and implement successful active control systems in practice and detail the pitfalls one must avoid to ensure a reliable and stable system. Extensively revised, updated, and expanded throughout, the second edition reflects the advances that have been made in algorithms, DSP hardware, and applications since the publication of the first edition.

This book is a companion text to Active Control of Sound by P.A. Nelson and S.J. Elliott, also published by Academic Press. It summarizes the principles underlying active vibration control and its practical applications by combining material from vibrations, mechanics, signal processing, acoustics, and control theory. The emphasis of the book is on the active control of waves in structures, the active isolation of vibrations, the use of distributed strain actuators and sensors, and the active control of structurally radiated sound. The feedforward control of deterministic disturbances, the active control of structural waves and the active isolation of vibrations are covered in detail, as well as the more conventional work on modal feedback. The principles of the transducers used as actuateors and sensors for such control strategies are also given an in-depth description. The reader will find particularly interesting the two chapters on the active control of sound radiation from structures: active structural acoustic control. The reason for controlling high frequency vibration is often to prevent sound radiation, and the principles and practical application of such techniques are presented here for both plates and cylinders. The volume is written in textbook style and is aimed at students, practicing engineers, and researchers. Combines material from vibrations, signal processing, mechanics, and controls Summarizes new research in the field

Understanding Active Noise Cancellation Provides a concise introduction to the fundamentals and applications of active control of vibration and sound for the non-expert. It is also a useful quick reference for the specialist engineer. The book emphasises the practical applications of technology, and complex control algorithms and structures are only discussed to the extent that they aid understanding. Extensive recommendations for further reading on the subject are provided, but the text will stand alone for those seeking an overview of the key issues: fundamentals, control systems, transducers, applications and possible future directions.

'The text is well written and supported by clear and useful illustrations. This would be a useful textbook for postgraduate or advanced undergraduate studies and would also make a good introductory text for engineers moving into the field. The literature survey and bibliography provide a useful starting point for further study.'The Aeronautical JournalActive Control of Aircraft Cabin Noise provides a bridge to fill the gap between robust control theory and practical applications of active noise control systems in aircraft cabin. Both the possibilities and limitations of structural solutions to enhance aircraft cabin comfort by reducing interior noise are discussed supported by a wide range of topics in engineering, from finite element modeling to multichannel adaptive feed-forward control, usually dealt separately in the literature. In addition, experimental noise attenuation results with passengers' subjective perceptions predicting the effects of cabin noise on comfort assessments is examined. Theoretical and experimental research is detailed enough to capture the interest of the non-expert in engineering who wishes to have an overview of some of the active noise control applications in aircraft. This book may be used as an advanced textbook by graduate and undergraduate students in aeronautical engineering, and would be an authoritative resource book for research into the subject.

By providing all the basic knowledge needed to assess how useful active noise control will be for a given problem, this book assists in the designing, setting up, and tuning of an active noise-control system. Written for students who have no prior knowledge of acoustics, signal processing, or noise control but who do have a reasonable grasp of basic physics and mathematics, the text is short and descriptive, leaving all mathematical details and proofs concerning vibrations, signal processing and the like to more advanced texts or research monographs. The book can thus be used in independent study, in a classroom with laboratories, or in conjunction with a kit for experiment or demonstration. Topics covered include basic acoustics, human perception and sound, sound intensity and related concepts, fundamentals of passive noise- control strategies, basics of digital systems and adaptive controllers, and active noise control systems.

Signal Processing for Active Control sets out the signal processing and automatic control techniques that are used in the analysis and implementation of active systems for the control of sound and vibration. After reviewing the performance limitations introduced by physical aspects of active control, Stephen Elliott presents the calculation of the optimal performance and the implementation of adaptive real time controllers for a wide variety of active control systems.Active sound and vibration control are technologically important problems with many applications. 'Active control' means controlling disturbance by superimposing a second disturbance on the original source of disturbance. Put simply, initial noise + other specially-generated noise or vibration = silence [or controlled noise]. This book presents a unified approach to techniques that are used in the analysis and implementation of different control systems. It includes practical examples at the end of each chapter to illustrate the use of various approaches.This book is intended for researchers, engineers, and students in the field of acoustics, active control, signal processing, and electrical engineering.

Structural vibrations have become the critical factor limiting the performance of many engineering systems, typical amplitudes ranging from meters to a few nanometers. Many acoustic nuisances in transportation systems and residential and office buildings are also related to structural vibrations. The active control of such vibrations involves nine orders of magnitude of vibration amplitude, which exerts a profound influence on the technology. Active vibration control is highly multidisciplinary, involving structural vibration, acoustics, signal processing, materials science, and actuator and sensor technology. Chapters 1-3 of this book provide a state-of-the-art introduction to active vibration control, active sound control, and active vibroacoustic control, respectively. Chapter 4 discusses actuator/sensor placement, Chapter 5 deals with robust control of vibrating structures, Chapter 6 discusses finite element modelling of piezoelectric continua and Chapter 7 addresses the latest trends in piezoelectric multiple-degree-of-freedom actuators/sensors. Chapters 8-12 deal with example applications, including semi-active joints, active isolation and health monitoring. Chapter 13 addresses MEMS technology, while Chapter 14 discusses the design of power amplifiers for piezoelectric actuators.

In Sound Propagation: An Impedance Based Approach, Professor Yang-Hann Kim introduces acoustics and sound fields by using the concept of impedance. Kim starts with vibrations and waves, demonstrating how vibration can be envisaged as a kind of wave, mathematically and physically. One-dimensional waves are used to convey the fundamental concepts. Readers can then understand wave propagation in terms of characteristic and driving point impedance. The essential measures for acoustic waves, such as dB scale, octave scale, acoustic pressure, energy, and intensity, are explained. These measures are all realized by one-dimensional examples, which provide mathematically simplest but clear enough physical insights. Kim then moves on to explaining waves on a flat surface of discontinuity, demonstrating how propagation characteristics of waves change in space when there is a distributed impedance mismatch. Next is a chapter on radiation, scattering, and diffraction, where Kim shows how these topics can be explained in a unified way, by seeing the changes of waves due to spatially distributed impedance. Lastly, Kim covers sound in closed space, which is considered to be a space that is surrounded by spatially distributed impedance, and introduces two spaces: acoustically large and small space. The bulk of the book is concerned with introducing core fundamental concepts, but the appendices are included as the essentials as well to cover other important topics to extend learning. Offers a less mathematically-intensive means to understand the subject matter Provides an excellent launching point for more advanced study or for review of the basics Based on classroom tested materials developed over the course of two decades Companion site for readers, containing animations and MATLAB code downloads Videos and impedance data available from the author's website Presentation slides available for instructor use Sound Propagation is geared towards graduate students and advanced undergraduates in acoustics, audio engineering, and noise control engineering. Practicing engineers and researchers in audio engineering and noise control, or students in engineering and physics disciplines, who want to gain an understanding of sound and vibration concepts, will also find the book to be a helpful resource.

This book presents a mechatronic approach to Active Noise Control (ANC). It describes the required elements of system theory, engineering acoustics, electroacoustics and adaptive signal processing in a comprehensive, consistent and systematic manner using a unified notation. Furthermore, it includes a design methodology for ANC-systems, explains its application and describes tools to be used for ANC-system design. From the research point of view, the book presents new approaches to sound source localization in weakly damped interiors. One is based on the inverse finite element method, the other is based on a sound intensity probe with an active free field. Furthermore, a prototype of an ANC-system able to reach the physical limits of local (feed-forward) ANC is described. This is one example for applied research in ANC-system design. Other examples are given for (i) local ANC in a semi-enclosed subspace of an aircraft cargo hold and (ii) for the combination of audio entertainment with ANC.