Acoustics: Sound Fields, Transducers and Vibration

Description

Acoustics: Sound Fields, Transducers and Vibration, Second Edition guides readers through the basics of sound fields, the laws governing sound generation, radiation, and propagation, and general terminology. Specific sections cover microphones (electromagnetic, electrostatic, and ribbon), earphones, and horns, loudspeaker enclosures, baffles and transmission lines, miniature applications (e.g. MEMS microphones and micro speakers in tablets and smart phones), sound in enclosures of all sizes, such as school rooms, offices, auditoriums and living rooms, and fluid-structure interaction. Numerical examples and summary charts are given throughout the text to make the material easily applicable to practical design. New to this edition: A chapter on electrostatic loudspeakers A chapter on vibrating surfaces (membranes, plates, and shells) Readers will find this to be a valuable resource for experimenters, acoustical consultants, and to those who anticipate being engineering designers of audio equipment. It will serve as both a text for students in engineering departments and as a valuable reference for practicing engineers. Cover Cover Details Acoustics: Sound Fields, Transducers and Vibration Copyright Preface to the second edition Preface to the first edition Acknowledgments One. Introduction and terminology Part I: Introduction 1.1 A little history 1.2 What is sound? 1.3 Propagation of sound through gas 1.4 Measurable aspects of sound Part II: Terminology 1.5 General Acoustic Acoustical Imaginary unit Harmonically varying quantity Instantaneous value Root mean square value 1.6 Standard International (SI) units 1.7 Pressure and density Static pressure (P0) Microbar (μbar) Instantaneous sound pressure [p(t)] Effective sound pressure (prms) Density of air (ρ0) 1.8 Speed and velocity Speed of sound (c) Instantaneous particle velocity (particle velocity) [u(t)] Effective particle velocity (urms) Instantaneous volume velocity [U(t)] 1.9 Impedance Acoustic impedance (ZA) (American standard acoustic impedance) Specific acoustic impedance (Zs) Mechanical impedance (ZM) Characteristic impedance (ρ0c) 1.10 Intensity, energy density, and levels Sound intensity (I) Sound energy density (D) Electric power level or acoustic intensity level Sound pressure level Intensity level (IL) Acoustic power level (PWL) Sound level Band power level (PWLn) Band pressure level (BPLn) Power spectrum level Pressure spectrum level Notes Two. The wave equation and solutions Part III: The wave equation 2.1 Introduction 2.2 Derivation of the wave equation 2.2.1 The equation of motion 2.2.2 The gas law 2.2.3 The continuity equation 2.2.4 The wave equation in rectangular coordinates 2.2.5 The wave equation in cylindrical coordinates 2.2.6 The wave equation in spherical coordinates 2.2.7 General one-dimensional wave equation (Webster's equation) [6] Part IV: Solutions of the wave equation in one dimension 2.3 General solutions of the one-dimensional wave equation 2.3.1 General solution 2.3.2 Steady-state solution 2.4 Solution of wave equation for air in a tube terminated by an impedance Particle velocity Transmitted and reflected pressures Impedance Impedance measurement Rigid termination (infinite impedance) Sound pressure Specific acoustic impedance 2.5 Impedance of a closed tube using the inhomogeneous wave equation Boundary conditions Solution of the inhomogeneous wave equation for a closed tube Impedance of the closed tube Expansions for cot and csc 2.6 Impedance of an open tube using the inhomogeneous wave equation Solution of the inhomogeneous wave equation for an open tube Impedance of the open tube Expansion for tan 2.7 Solution of wave equation for air in a tube filled with absorbent material 2.8 Freely traveling plane wave Sound pressure Particle velocity Specific acoustic impedance 2.9 Freely traveling cylindrical wave Sound pressure Particle velocity Specific acoustic impedance 2.10 Freely traveling spherical wave Sound pressure Particle velocity Specific acoustic impedance Part V: Solutions of the Helmholtz wave equation in three dimensions 2.11 Rectangular coordinates The plane wave equation in x The plane wave equation in y The plane wave equation in z 2.12 Cylindrical coordinates The radial equation in w The azimuthal equation in φ The axial equation in z 2.13 Spherical coordinates The radial equation in r The inclination equation in θ The azimuth equation in φ Notes Three. Electromechanoacoustical circuits Part VI: Mechanical circuits 3.1 Introduction 3.2 Physical and mathematical meanings of circuit elements 3.3 Mechanical elements Mechanical impedance ZM and mechanical admittance YM Mass MM Mechanical compliance CM Mechanical resistance RM and mechanical conductance GM Mechanical generators Levers Simple lever Floating lever Part VII: Acoustical circuits 3.4 Acoustical elements Acoustic mass MA Acoustic compliance CA Acoustic resistance RA and acoustic conductance GA Acoustic generators Mechanical rotational systems Part VIII: Transducers 3.5 Electromechanical transducers Electromagnetic-mechanical transducer Electrostatic-mechanical transducer 3.6 Mechanoacoustic transducer 3.7 Examples of transducer calculations Part IX: Circuit theorems, energy, and power 3.8 Conversion from admittance-type analogies to impedance-type analogies 3.9 Thévenin's theorem 3.10 Transducer impedances Transmission matrix for an electrical two-port network Transmission matrix for an electromagnetic-mechanical transducer Impedance matrix for an electromagnetic-mechanical transducer Transmission matrix for an electrostatic-mechanical transducer Impedance matrix for an electrostatic-mechanical transducer Analogous circuits for the two-port network using z-parameters [12] Notes Four. Acoustic components 4.1 Introduction Part X: Acoustic elements 4.2 Acoustic mass (inertance) Tube of medium diameter 4.3 Acoustic compliances Limitations on an acoustic compliance Series acoustic compliance 4.4 Acoustic resistances Tube of small diameter [0.005