2-1 质点自由振动.pdf

声学基础 Fundamentals of Acoustics 第二章 质点振动系统 第1讲 质点自由振动 厦门大学海洋与地球学院 许肖梅 Xu Xiaomei Email: xmxu@xmu.edu.cn Introduction: Acoustics may be defined as the generation, transmission, and reception of energy in the form of vibrating waves in matter. This chapter introduces the basic mathematics of simple vibrating systems.  The treatment is limited to electromechanical devices because these are by far the most widely used and lend themselves to many purposes. 声学基础 Fundamentals of Acoustics According to function, we may group an electromechanical source into three sections: an electrical section with two or more terminals. a mechanical section with two or more terminals. a section between, which has the capability of converting events at one set of terminals into related events at the other set. 声学基础 Fundamentals of Acoustics The acoustical engineer is interested in the fidelity of reproduction of sound The conversion of mechanical and electrical energy into acoustical energy, The design of acoustical transducers. The architect is more interested in the absorption and isolation of sound in buildings, and in controlled reverberation and echo prevention in auditoriums. The musician likes to know how to obtain rhythmic combinations of tones through vibrations of strings, air columns. 声学基础 Fundamentals of Acoustics 1. Waves Sound does not consist of air moving towards us in bulk. It travels through the air as a sound wave. As a vibrating body moves forward from its static equilibrium position, it pushes the air before it and compresses it . At the same time, a rarefaction occurs immediately behind the body, and air rushes