Bølgemekanik (vibration og akustik)

The following topics are presented in this book:introduction to waves and their propertiesacoustic waveshuman acoustics and phonometric systemsroom acoustics and hints of building acoustic design

This book provides the material for an introductory course in engineering acoustics for students with basic knowledge in mathematics. It is based on extensive teaching experience at the university level. Under the guidance of an academic teacher it is su?cient as the sole te- book for the subject. Each chapter deals with a well de?ned topic and r- resents the material for a two-hour lecture. The chapters alternate between more theoretical and more application-oriented concepts. For the purpose of self-study, the reader is advised to use this text in parallel with further introductory material. Some suggestions to this end are given in Appendix 15. 3. The authors thank Dorea Ruggles for providing substantial stylistic re?- ments. Further thanks go to various colleagues and graduate students who most willingly helped with corrections and proof reading. Nevertheless, the authors assume full responsibility for all contents. Bochum and Troy, Jens Blauert February 2008 Ning Xiang Contents 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1. 1 De?nition of Three Basic Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1. 2 Specialized Areas within Acoustics . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. 3 About the History of Acoustics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. 4 Relevant Quantities in Acoustics . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1. 5 Some Numerical Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1. 6 Levels and Logarithmic Frequency Intervals . . . . . . . . . . . . . . . . . 8 1. 7 Double-Logarithmic Plots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2 Mechanic and Acoustic Oscillations . . . . . . . . . . . . . . . . . . . . . . . . 13 2. 1 Basic Elements of Linear, Oscillating, Mechanic Systems . . . . . 14 2. 2 Parallel Mechanic Oscillators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2. 3 Free Oscillations of Parallel Mechanic Oscillators . . . . . . . . . . . . 17 2. 4 Forced Oscillation of Parallel Mechanic Oscillators . . . . . . . . . . .

This book delivers a comprehensive and up-to-date treatment of practical applications of metamaterials, structured media, and conventional porous materials. With increasing levels of urbanization, a growing demand for motorized transport, and inefficient urban planning, environmental noise exposure is rapidly becoming a pressing societal and health concern. Phononic and sonic crystals, acoustic metamaterials, and metasurfaces can revolutionize noise and vibration control and, in many cases, replace traditional porous materials for these applications.In this collection of contributed chapters, a group of international researchers reviews the essentials of acoustic wave propagation in metamaterials and porous absorbers with viscothermal losses, as well as the most recent advances in the design of acoustic metamaterial absorbers. The book features a detailed theoretical introduction describing commonly used modelling techniques such as plane wave expansion, multiple scattering theory, and the transfer matrix method. The following chapters give a detailed consideration of acoustic wave propagation in viscothermal fluids and porous media, and the extension of this theory to non-local models for fluid saturated metamaterials, along with a description of the relevant numerical methods. Finally, the book reviews a range of practical industrial applications, making it especially attractive as a white book targeted at the building, automotive, and aeronautic industries.

Listening, Belonging, and Memory puts connected listening at the center of current debates around whose voices might be listened to, who by, and why. Arguing that listening has to be understood in relation to the self, nation, age, witnessing, and memory, it uses examples from digital storytelling, listening projects, and critical media analysis to highlight connections between listening and power. It centers on voices, stories, and silence, how they interweave, and are activated, maneuvered, reconfigured, and denied. It focuses on the small, microengagementsthat crouch within the superstructures of violent border control and the censorious policing of sonic citizenry, identifying cracks in the reshuffling of histories and hierarchies that connected listening affords.

This book, the first dedicated to the topic, provides a comprehensive treatment of forward stimulated Brillouin scattering (SBS) in standard optical fibers. SBS interactions between guided light and sound waves have drawn much attention for over fifty years, and optical fibers provide an excellent playground for the study of Brillouin scattering as they support guided modes of both wave types and provide long interaction lengths. This book is dedicated to forward SBS processes that are driven by co-propagating optical fields. The physics of forward SBS is explained in detail, starting from the fundamentals of interactions between guided optical and acoustic waves, with emphasis given to the acoustic modes that are stimulated in the processes. The realization of forward SBS in standard single-mode, polarization-maintaining and multi-core fibers is then discussed in depth. Innovative potential applications in sensors, monitoring of coating layers, lasers, and radio-frequency oscillators are presented. This book introduces the subject to graduate students in optics and applied physics, and it will be of interest to scientists working in fiber-optics, nonlinear optics and opto-mechanics.Provides the first treatment of forward stimulated Brillouin scattering (SBS) in book form;Reflects the dramatic recent increase in interest in forward SBS processes , driven in part by the promise of new fiber sensing concepts;Delivers a solid and comprehensive grounding in the physics of forward SBS along with detailed experimental set-ups, measurement protocols, and applications.