Noise Reduction Analysis (Physics)

Written by a noted authority in the subject area, this book is a comprehensive study of the theory and practical application of noise reduction to numerous fields. It may be used as a reference by scientists and engineers or in a senior-undergraduate or graduate-level course. The first six chapters deal with the basic mechanisms of sound absorption by which acoustic energy is converted into heat in viscous and thermal boundaries in a sound field. The second part covers duct attenuators with a discussion of how their performance is described and measured. The main part of each chapter is planned to be descriptive, and contains numerical results that should be of direct interest for design work. Mathematical analysis is placed at the end of the chapters. Preface......Page 6 Contents......Page 8 List of Figures......Page 16 Part I: Absorbers......Page 22 1.1 GENERAL COMMENTS......Page 24 1.2 TERMINOLOGY AND NOTATION......Page 25 2.1 BRIEF SUMMARY......Page 28 2.2 STEADY FLOW THROUGH A (NARROW) CHANNEL......Page 30 2.3 ACOUSTIC BOUNDARY LAYERS......Page 31 2.4 SOUND PROPAGATION IN A NARROW CHANNEL......Page 35 2.5 IMPEDANCES......Page 42 2.6 VISCO-THERMAL ADMITTANCE AND ABSORPTION COEFFICIENT OF A RIGID WALL......Page 52 2.7 MATHEMATICAL SUPPLEMENT......Page 55 3.1 INTRODUCTION AND BRIEF SUMMARY......Page 74 3.2 RIGID SINGLE SHEET WITH CAVITY BACKING......Page 77 3.3 FLEXIBLE POROUS SHEET WITH CAVITY BACKING......Page 87 3.4 LATTICE ABSORBERS......Page 98 3.5 ‘VOLUME’ ABSORBERS......Page 103 3.6 MATHEMATICAL SUPPLEMENT......Page 108 4.1 INTRODUCTION AND SUMMARY......Page 126 4.2 ABSORPTION AND SCATTERING......Page 127 4.3 ACOUSTIC NONLINEARITY......Page 137 4.4 EFFECTS OF FLOW......Page 143 4.5 MATHEMATICAL SUPPLEMENT......Page 153 5.1 INTRODUCTION AND SUMMARY......Page 164 5.2 THE SLOT ABSORBER......Page 167 5.3 ISOTROPIC POROUS LAYER, PHYSICAL PARAMETERS......Page 175 5.4 WAVE MOTION......Page 178 5.5 ABSORPTION SPECTRA......Page 182 5.6 EFFECT OF REFRACTION IN GRAZING FLOW......Page 194 5.7 MATHEMATICAL SUPPLEMENT......Page 202 6.1 INTRODUCTION AND SUMMARY......Page 218 6.2 COUPLED WAVES......Page 219 6.3 DISPERSION RELATION......Page 220 6.4 FIELD DISTRIBUTIONS......Page 222 6.5 ABSORPTION SPECTRA......Page 225 6.6 NONLINEAR EFFECTS AND SHOCK WAVE REFLECTION......Page 232 6.7 MEASUREMENT OF COMPLEX ELASTIC MODULUS......Page 238 6.8 MATHEMATICAL SUPPLEMENT......Page 240 Part II: Duct Attenuators......Page 254 7.1 PRELIMINARIES......Page 256 7.2 WAVE MODES......Page 259 7.3 MEASURES OF SILENCER PERFORMANCE......Page 261 7.4 LINED DUCTS......Page 270 7.6 ACOUSTICALLY EQUIVALENT SILENCERS......Page 272 7.7 ADDITIONAL COMMENTS ON SILENCER TESTING......Page 273 8.1 ATTENUATION MECHANISMS......Page 276 8.2 RECTANGULAR DUCTS......Page 278 8.4 DUCTS IN SERIES AND IN PARALLEL......Page 295 8.5 DUCT LINER CONFIGURATIONS......Page 296 8.6 EFFECTS OF HIGHER MODES AND FLOW......Page 303 8.7 LIQUID PIPE LINES, ELEMENTARY ASPECTS......Page 314 9.1 UNIFORM DUCT SECTION......Page 320 9.2 EXPANSION CHAMBER......Page 324 9.3 ‘CONTRACTION’ CHAMBER......Page 326 9.4 SIDE-BRANCH RESONATOR IN A DUCT......Page 328 9.5 PERFORATED PLATE......Page 333 9.6 ATTENUATION IN TURBULENT FLOWIN DUCTS......Page 338 9.7 NONLINEAR ATTENUATION......Page 340 9.8 ON AIR INDUCTION ACOUSTICS......Page 341 10.1 SUPPLEMENT TO SECTION 8.1......Page 352 10.2 SUPPLEMENT TO SECTION 8.2......Page 353 10.3 SUPPLEMENT TO SECTION 8.3, OTHER DUCT TYPES......Page 362 10.4 SUPPLEMENT TO SECTION 8.6, HIGHER MODES AND FLOW......Page 367 10.5 SUPPLEMENT TO SECTION 8.7, LIQUID PIPE LINES......Page 370 10.6 SUPPLEMENT TO SECTION 9.1, UNIFORM DUCT......Page 377 10.7 SUPPLEMENT TO SECTION 9.6, ATTENUATION IN TURBULENT DUCT FLOW......Page 378 A.1 INTRODUCTION......Page 382 A.2 APPLICATION OF MATRICES......Page 383 A.3 COMMONLY USED MATRICES......Page 391 B.1 SIMPLE METHOD FOR STEADY FLOW......Page 410 B.2 SIMPLE METHOD FOR OSCILLATORY FLOW......Page 416 C.1 ‘THE ABSORPTION COEFFICIENT PROBLEM’......Page 424 C.2 LISTS OF REFERENCES......Page 428 D.1 BRIEF HISTORICAL NOTE......Page 450 D.2 REFERENCES......Page 451 Index......Page 460