Acoustics for Engineers - Troy Lectures

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 . . . . . . . . . . .