[POD] Foundations of Engineering Acoustics

Foundations of Engineering Acoustics takes the reader on a journey from a qualitative introduction to the physical nature of sound, explained in terms of common experience, to mathematical models and analytical results which underlie the techniques applied by the engineering industry to improve the acoustic performance of their products. The book is distinguished by extensive descriptions and explanations of audio-frequency acoustic phenomena and their relevance to engineering, supported by a wealth of diagrams, and by a guide for teachers of tried and tested class demonstrations and laboratory-based experiments. Foundations of Engineering Acoustics is a textbook suitable for both senior undergraduate and postgraduate courses in mechanical, aerospace, marine, and possibly electrical and civil engineering schools at universities. It will be a valuable reference for academic teachers and researchers and will also assist Industrial Acoustic Group staff and Consultants. Comprehensive and up-to-date: broad coverage, many illustrations, questions, elaborated answers, references and a bibliography Introductory chapter on the importance of sound in technology and the role of the engineering acoustician Deals with the fundamental concepts, principles, theories and forms of mathematical representation, rather than methodology Frequent reference to practical applications and contemporary technology Emphasizes qualitative, physical introductions to each principal as an entreacute;e to mathematical analysis for the less theoretically oriented readers and courses Provides a 'cook book' of demonstrations and laboratory-based experiments for teachers Useful for discussing acoustical problems with non-expert clients/managers because the descriptive sections are couched in largely non-technical language and any jargon is explained Draws on the vast pedagogic experience of the writer

Preface xiii
Acknowledgements xix
Sound Engineering 1 (5)
The importance of sound 1 (1)
Acoustics and the engineer 2 (1)
Sound the servant 3 (3)
The Nature of Sound and Some Sound Wave 6 (17)
Phenomena
Introduction 6 (1)
What is sound? 6 (1)
Sound and vibration 7 (2)
Sound in solids 9 (1)
A qualitative introduction to wave phenomena 9 (12)
Wavefronts 9 (3)
Interference 12 (2)
Reflection 14 (2)
Scattering 16 (1)
Diffraction 17 (1)
Refraction 18 (2)
The Doppler effect 20 (1)
Convection 20 (1)
Some more common examples of the behaviour 21 (2)
of sound waves
Sound in Fluids 23 (25)
Introduction 23 (1)
The physical characteristics of fluids 23 (1)
Molecules and particles 24 (1)
Fluid pressure 25 (1)
Fluid temperature 25 (1)
Pressure, density and temperature in sound 26 (3)
waves in a gas
Particle motion 29 (1)
Sound in liquids 29 (1)
Mathematical models of sound waves 30 (18)
The plane sound wave equation 30 (4)
Solutions of the plane wave equation 34 (1)
Harmonic plane waves: sound pressure 35 (3)
Plane waves: particle velocity 38 (1)
The wave equation in three dimensions 39 (2)
Plane waves in three dimensions 41 (2)
The wave equation in spherical coordinates 43 (1)
The spherically symmetric sound field 44 (1)
Particle velocity in the spherically 45 (1)
symmetric sound field
Other forms of sound field 46 (2)
Impedance 48 (26)
Introduction 48 (2)
Some simple examples of the utility of 50 (2)
impedance
Mechanical impedance 52 (4)
Impedance of lumped structural elements 53 (3)
Forms of acoustic impedance 56 (16)
Impedances of lumped acoustic elements 57 (6)
Specific acoustic impedance of fluid in a 63 (3)
tube at low frequency
Normal specific acoustic impedance 66 (1)
Radiation impedance 67 (1)
Acoustic impedance 68 (1)
Line and surface wave impedance 68 (3)
Modal radiation impedance 71 (1)
An application of radiation impedance of a 72 (1)
uniformly pulsating sphere
Radiation efficiency 72 (2)
Sound Energy and Intensity 74 (22)
The practical importance of sound energy 74 (1)
Sound energy 75 (1)
Transport of sound energy: sound intensity 76 (2)
Sound intensity in plane wave fields 78 (4)
Intensity and mean square pressure 82 (1)
Examples of ideal sound intensity fields 82 (6)
The point monopole 82 (2)
The compact dipole 84 (1)
Interfering monopoles 85 (2)
Intensity distributions in orthogonally 87 (1)
directed harmonic plane wave fields
Sound intensity measurement 88 (3)
Determination of source sound power using 91 (1)
sound intensity measurement
Other applications of sound intensity 92 (4)
measurement
Sources of Sound 96 (44)
Introduction 96 (1)
Qualitative categorization of sources 97 (6)
Category 1 sources 98 (2)
Category 2 sources 100 (3)
Category 3 sources 103 (1)
The inhomogeneous wave equation 103 (3)
Sound radiation by foreign bodies 104 (1)
Boundary `sources' can reflect or absorb 105 (1)
energy
Ideal elementary source models 106 (18)
The Dirac delta function 106 (2)
The point monopole and the pulsating 108 (3)
sphere
Acoustic reciprocity 111 (1)
External forces on a fluid and the 112 (4)
compact dipole
The oscillating sphere 116 (2)
Boundary sources 118 (3)
Free-field and other Green's functions 121 (1)
The Rayleigh integrals 122 (2)
Sound radiation from vibrating plane 124 (2)
surfaces
The vibrating circular piston and the cone 126 (3)
loudspeaker
Directivity and sound power of distributed 129 (5)
sources
Sound power of a source in the presence 131 (3)
of a second source
Zones of a sound field radiated by a 134 (1)
spatially extended source
Experimental methods for source sound power 135 (1)
determination
Source characterization 136 (4)
Sound Absorption and Sound Absorbers 140 (41)
Introduction 140 (1)
The effects of viscosity, thermal diffusion 141 (6)
and relaxation processes on sound in gases
The origin of gas viscosity 141 (1)
The effects of thermal diffusion 142 (1)
The effect of molecular relaxation 143 (1)
Sound energy dissipation at the rigid 143 (3)
boundary of a gas
Acoustically induced boundary layers in a 146 (1)
gas-filled tube
Forms of porous sound absorbent material 147 (2)
Macroscopic physical properties of porous 149 (4)
sound-absorbing materials
Porosity 149 (1)
Flow resistance and resistivity 150 (1)
Structure factor 151 (2)
The modified equation for plane wave sound 153 (3)
propagation in gases contained within rigid
porous materials
Equation of mass conservation 153 (1)
Momentum equation 154 (1)
The modified plane wave equation 154 (1)
Harmonic solution of the modified plane 154 (2)
wave equation
Sound absorption by a plane surface of 156 (7)
uniform impedance
The local reaction model 156 (2)
Sound power absorption coefficient of a 158 (4)
locally reactive surface
Wave impedance 162 (1)
Sound absorption by thin porous sheets 163 (4)
The immobile sheet in free field 163 (1)
The limp sheet in free field 164 (2)
The effect of a rigid wall parallel to a 166 (1)
thin sheet
Sound absorption by thick sheets of rigid 167 (4)
porous material
The infinitely thick `sheet' 167 (1)
The sheet of finite thickness 168 (1)
The effect on a backing cavity on the 169 (2)
sound absorption of a sheet of porous
material
Sound absorption by flexible cellular and 171 (1)
fibrous materials
The effect of perforated cover sheets on 172 (2)
sound absorption by porous materials
Non-porous sound absorbers 174 (4)
Helmholtz resonators 174 (2)
Panel absorbers 176 (2)
Methods of measurement of boundary 178 (3)
impedance and absorption coefficient
The impedance tube 178 (1)
Reverberation room method 179 (2)
Sound in Waveguides 181 (55)
Introduction 181 (2)
Plane wave pulses in a uniform tube 183 (4)
Plane wave modes and natural frequencies of 187 (7)
fluid in uniform waveguides
Conservative terminations 187 (4)
Non-conservative terminations 191 (3)
Response to harmonic excitation 194 (5)
Impedance model 194 (2)
Harmonic response in terms of Green's 196 (3)
functions
A simple case of structure-fluid interaction 199 (2)
Plane waves in ducts that incorporate 201 (10)
impedance discontinuities
Insertion loss and transmission loss 201 (1)
Transmission of plane waves through an 202 (3)
abrupt change of cross-sectional area and
an expansion chamber
Series networks of acoustic transmission 205 (1)
lines
Side branch connections to uniform 206 (2)
acoustic waveguides
The side branch tube 208 (2)
The side branch orifice 210 (1)
The Helmholtz resonator side branch 210 (1)
Bends in otherwise straight uniform 211 (1)
waveguides
Transverse modes of uniform acoustic 211 (9)
waveguides
The uniform two-dimensional waveguide 211 (6)
with rigid walls
The uniform two-dimensional waveguide 217 (1)
with finite impedance boundaries
The uniform waveguide of rectangular 218 (1)
cross-section with rigid walls
The uniform waveguide of circular 218 (2)
cross-section with rigid walls
Harmonic excitation of waveguide modes 220 (2)
Energy flux in a waveguide of rectangular 222 (2)
cross-section with rigid walls
Examples of the sound attenuation 224 (3)
characteristics of lined ducts and splitter
attenuators
Acoustic horns 227 (9)
Applications 227 (1)
The horn equation 228 (8)
Sound in Enclosures 236 (34)
Introduction 236 (3)
Some general features of sound fields in 239 (4)
enclosures
Apology for the rectangular enclosure 243 (1)
The impulse response of fluid in a 243 (2)
reverberant rectangular enclosure
Acoustic natural frequencies and modes of 245 (3)
fluid in a rigid-walled rectangular
enclosure
Modal energy 248 (1)
The effects of finite wall impedance on 249 (2)
modal energy-time dependence in free
vibration
The response of fluid in a rectangular 251 (2)
enclosure to harmonic excitation by a point
monopole source
The sound power of a point monopole in a 253 (1)
reverberant enclosure
Sound radiation into an enclosure by the 254 (2)
vibration of a boundary
Probabilistic wave field models for 256 (6)
enclosed sound fields at high frequency
The modal overlap factor and response 256 (1)
uncertainty
High-frequency sound field statistics 257 (1)
The diffuse field model 258 (4)
Applications of the diffuse field model 262 (5)
Steady state diffuse field energy, 262 (1)
intensity and enclosure absorption
Reverberation time 263 (2)
Steady state source sound power and 265 (2)
reverberant field energy
A brief introduction to geometric (ray) 267 (3)
acoustics
Structure-borne Sound 270 (45)
The nature and practical importance of 270 (4)
structure-borne sound
Emphasis and content of the chapter 274 (2)
The energy approach to modelling 276 (2)
structure-borne sound
Quasi-longitudinal waves in uniform rods 278 (1)
and plates
The bending wave in uniform homogeneous 279 (6)
beams
A review of the roles of direct and shear 279 (2)
stresses
Shear force and bending moment 281 (3)
The beam bending wave equation 284 (1)
Harmonic solutions of the bending wave 284 (1)
equation
The bending wave in thin uniform 285 (1)
homogeneous plates
Transverse plane waves in flat plates 286 (1)
Dispersion curves, wavenumber vector 287 (3)
diagrams and modal density
Structure-borne wave energy and energy flux 290 (3)
Quasi-longitudinal waves 290 (1)
Bending waves in beams 291 (2)
Bending waves in plates 293 (1)
Mechanical impedances of infinite, uniform 293 (4)
rods, beams and plates
Impedance of quasi-longitudinal waves in 293 (1)
rods
Impedances of beams in bending 294 (2)
Impedances of thin, uniform, flat plates 296 (1)
in bending
Impedance and modal density 297 (1)
Wave energy transmission through junctions 297 (1)
between structural components
Impedance, mobility and vibration isolation 298 (3)
Structure-borne sound generated by impact 301 (3)
Sound radiation by vibrating flat plates 304 (11)
The critical frequency and radiation 304 (2)
cancellation
Analysis of modal radiation 306 (4)
Physical interpretations and practical 310 (5)
implications
Transmission of Sound through Partitions 315 (37)
Practical aspects of sound transmission 315 (1)
through partitions