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E-raamat: Duct Acoustics: Fundamentals and Applications to Mufflers and Silencers

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  • Ilmumisaeg: 13-May-2021
  • Kirjastus: Cambridge University Press
  • Keel: eng
  • ISBN-13: 9781108899628
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Duct Acoustics: Fundamentals and Applications to Mufflers and SilencersSuurem pilt
  • Formaat: PDF+DRM
  • Ilmumisaeg: 13-May-2021
  • Kirjastus: Cambridge University Press
  • Keel: eng
  • ISBN-13: 9781108899628
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Using a hands-on approach, this self-contained reference covers topics ranging from the foundations of duct acoustics to acoustic design of mufflers and silencers. A perfect tool for engineers and researchers.

foundations of duct acoustics to the acoustic design of duct systems, through practical modeling, optimization and measurement techniques. Discover in-depth analyses of one- and three-dimensional models of sound generation, propagation and radiation, as techniques for assembling acoustic models of duct systems from simpler components are described. Identify the weaknesses of mathematical models in use and improve them by measurement when needed. Cope with challenges in acoustic design, and improve understanding of the underlying physics, by using the tools described. An essential reference for engineers and researchers who work on the acoustics of fluid machinery ductworks.

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Understand topics ranging from the foundations of duct acoustics to acoustic design of mufflers and silencers with this hands-on reference.
Preface xvii
1 Some Preliminaries
1(22)
1.1 Introduction to the Linear Theory of Sound Wave Motion
1(7)
1.1.1 Linearization Hypothesis
1(1)
1.1.2 Partitioning Turbulent Fluctuations
2(2)
1.1.3 Linearization of Inviscid Fluid Flow
4(3)
1.1.4 Evolution of Non-Linear Waves
7(1)
1.2 Representation of Acoustic Waves in the Frequency Domain
8(6)
1.2.1 Fourier Transform
8(2)
1.2.2 Periodic Functions
10(1)
1.2.3 Impulse Sampling
11(1)
1.2.4 Power Spectral Density
12(2)
1.3 Representation of Waves in the Wavenumber Domain
14(1)
1.3.1 Spatial Fourier Transform
14(1)
1.3.2 Briggs' Criterion
15(1)
1.4 Intensity and Power of Sound Waves
15(4)
1.5 Introduction to the Linear System View of Duct Acoustics
19(2)
References
21(2)
2 Introduction To Acoustic Block Diagrams
23(36)
2.1 Introduction
23(2)
2.2 Classification of Acoustic Models of Ducts
25(4)
2.2.1 Classification by Number of Ports
25(1)
2.2.2 Classification by Type of Port
26(1)
2.2.2.1 One-Dimensional Elements
27(1)
2.2.2.2 Modal Elements
27(2)
2.3 Mathematical Models of Acoustic Elements
29(4)
2.3.1 One-Port Elements
29(2)
2.3.2 Two-Port Elements
31(1)
2.3.3 Multi-Port Elements
32(1)
2.4 Assembly of Blocks
33(11)
2.4.1 Assembly of Two-Ports
34(2)
2.4.2 Assembly of Multi-Ports
36(5)
2.4.3 Optimization of Global Matrix Size
41(1)
2.4.4 Contraction of Assembled Modal Two-Ports
42(2)
2.5 Acoustic Elements Based on Numerical Methods
44(7)
2.5.1 The Finite Element Method
45(4)
2.5.2 The Boundary Element Method
49(2)
2.6 Programming Considerations
51(7)
References
58(1)
3 Transmission Of Low-Frequency Sound Waves In Ducts
59(66)
3.1 Introduction
59(1)
3.2 One-Dimensional Theory of Sound Propagation in Ducts
60(5)
3.2.1 Unsteady Flow Equations
60(3)
3.2.2 Equations Governing Acoustic Wave Motion
63(2)
3.3 Solution of Linearized Acoustic Equations
65(7)
3.3.1 Homogeneous Ducts (ε' = 0)
66(1)
3.3.1.1 Uniform Ducts
67(1)
3.3.1.2 Homogeneous Non-Uniform Ducts
68(1)
3.3.2 Inhomogeneous Ducts (ε' ≠ 0)
68(1)
3.3.3 Numerical Matrizant Method
69(3)
3.4 Time-Averaged Power of One-Dimensional Acoustic Waves
72(1)
3.5 Hard-Walled Uniform Ducts
73(7)
3.5.1 Wave Transfer Matrix
74(1)
3.5.2 Traveling Waves and Direction of Propagation
75(2)
3.5.3 Reflection Coefficient and Standing Waves
77(2)
3.5.4 Lumped Acoustic Elements
79(1)
3.6 Hard-Walled Homogeneous Ducts with Non-Uniform Cross Section
80(5)
3.6.1 Wave Transfer Matrix
81(3)
3.6.2 High Frequency Approximation
84(1)
3.7 Ducts Packed with Porous Material
85(2)
3.8 Acoustic Boundary Conditions on Duct Walls
87(5)
3.8.1 Impermeable Walls
87(1)
3.8.1.1 No-Slip Model
87(1)
3.8.1.2 Full-Slip Model
88(1)
3.8.1.3 Partial-Slip Model
88(1)
3.8.1.4 Rough-Wall Model
89(1)
3.8.1.5 Unified Boundary Condition
90(1)
3.8.2 Permeable Walls
91(1)
3.9 Homogeneous Ducts with Impermeable Finite Impedance Walls
92(14)
3.9.1 Non-Uniform Duct
93(2)
3.9.2 Uniform Duct
95(2)
3.9.2.1 Direction of Propagation
97(1)
3.9.2.2 Wave Equation
98(1)
3.9.2.3 Impedance Eduction Formula
98(1)
3.9.2.4 Peripherally Non-Uniform Wall Impedance
98(1)
3.9.3 Finite Wall Impedance Models
99(1)
3.9.3.1 Lined Impermeable Walls
99(3)
3.9.3.2 Permeable Rigid Porous Walls
102(1)
3.9.3.3 Perforated Rigid Walls
103(2)
3.9.3.4 Turbulent Boundary Layer Over Rigid Walls
105(1)
3.9.3.5 Elastic Walls
105(1)
3.10 Inhomogeneous Ducts
106(6)
3.10.1 Linearized Energy Equation
106(1)
3.10.2 Matrizant of a Duct with Finite Impedance Walls
107(2)
3.10.3 Hard-Walled Ducts with Mean Temperature Gradient
109(3)
3.11 Ducts with Two-Phase Flow
112(4)
3.12 Ducts with Time-Variant Mean Temperature
116(6)
References
122(3)
4 Transmission Of One-Dimensional Waves In Coupled Ducts
125(48)
4.1 Introduction
125(1)
4.2 Quasi-Static Theory of Wave Transmission at Compact Junctions
125(4)
4.2.1 Quasi-Static Conservation Laws
125(3)
4.2.2 Transformation to Pressure Wave Components
128(1)
4.3 Two Ducts Coupled by Forming Sudden Area Change
129(14)
4.3.1 Open Area Change
131(3)
4.3.1.1 The Case of Zero Mean Flow
134(1)
4.3.1.2 Core-Flow Model
134(5)
4.3.1.3 Effect of Inner Duct Wall Thickness
139(1)
4.3.2 Closed Area Changes
140(1)
4.3.3 End-Correction
141(2)
4.4 Sudden Area Changes Formed by Multiple Ducts
143(4)
4.4.1 Identical Inner Ducts
144(1)
4.4.2 Staggered Inner Duct Extensions
145(1)
4.4.3 Duct Splits
146(1)
4.5 Wave Transmission Through a Perforated Rigid Baffle
147(3)
4.5.1 Area-Change Model
148(1)
4.5.2 Lumped Impedance Model
149(1)
4.6 Wave Transmission in Junction Cavities
150(3)
4.6.1 Multi-Duct Junction
151(1)
4.6.2 Two-Duct Junction
152(1)
4.7 Continuously Coupled Perforated Ducts
153(9)
4.7.1 Single-Coupled Perforated Ducts
156(3)
4.7.1.1 Identical Perforated Ducts
159(1)
4.7.2 Double-Coupled Perforated Ducts
160(2)
4.8 Row-Wise Coupled Perforated Ducts
162(6)
4.8.1 Wave Transfer Across a Row of Apertures
163(2)
4.8.2 Single-Coupled n-Duct Section
165(1)
4.8.3 Double-Coupled n-Duct Section
166(1)
4.8.4 Wave Transfer Matrix of n-Duct Element
167(1)
4.9 Dissipative Units and Lined Ducts
168(1)
4.10 Wave Transfer Across Adiabatic Pressure Loss Devices
169(3)
References
172(1)
5 Resonators, Expansion Chambers And Silencers
173(65)
5.1 Introduction
173(4)
5.1.1 Mufflers and Silencers
173(1)
5.1.2 The System and Its Environment
174(3)
5.2 Transmission Loss
177(3)
5.2.1 Single-Frequency Analysis
177(2)
5.2.2 Overall Transmission Loss
179(1)
5.3 Duct Resonances
180(17)
5.3.1 Resonance and Anti-Resonance Frequencies
180(1)
5.3.2 Resonators
181(1)
5.3.3 Single-Duct Resonator
182(2)
5.3.4 Resonators with Open Outlet
184(1)
5.3.5 Helmholtz Resonator
185(2)
5.3.6 Transmission Loss of Resonators
187(2)
5.3.7 Interferential Resonator
189(1)
5.3.7.1 Wave Transfer Matrix of Parallel Two-Ports
190(2)
5.3.7.2 Wave Transfer Matrix of the HQ Tube
192(1)
5.3.7.3 Herschel-Quincke Tube Resonator
193(2)
5.3.8 Straight-Through Resonator
195(2)
5.4 Expansion Chambers
197(16)
5.4.1 Through-Flow Expansion Chambers
198(3)
5.4.2 Transmission Loss of Expansion Chambers
201(1)
5.4.3 Pure Expansion Chambers
202(1)
5.4.4 The Strongest Pure Expansion Chamber
203(2)
5.4.5 Tuning Inlet and Outlet Duct Extensions
205(2)
5.4.6 Effect of Inlet and Outlet Duct Configurations
207(1)
5.4.7 Division of a Pure Expansion Chamber
208(2)
5.4.8 Low-Frequency Response of Chambers
210(1)
5.4.9 Chambers with a Perforated Duct Bridge
211(2)
5.4.10 Packed Chambers
213(1)
5.5 Reciprocal Two-Ports
213(2)
5.6 Some Practical Issues
215(9)
5.6.1 Irregular Geometry
215(2)
5.6.2 Variable Mean Flow Conditions
217(2)
5.6.3 Multiple Outlet Ducts
219(4)
5.6.4 Flow Excited Resonators and Chambers
223(1)
5.7 Flow Rate and Back-Pressure Calculation
224(7)
5.7.1 Calculation of Mean Temperature Drop
230(1)
5.8 Shell Noise
231(5)
References
236(2)
6 Multi-Modal Sound Propagation In Ducts
238(88)
6.1 Introduction
238(1)
6.2 Uniform Ducts with Axial Mean Flow
239(4)
6.3 Boundary Condition on Impermeable Walls
243(4)
6.3.1 No-Slip Model
243(1)
6.3.2 Partial--Slip Model
244(1)
6.3.3 Ingard-Myers Model
244(1)
6.3.4 Modified Ingard--Myers Models
245(2)
6.4 Wave Transmission in a Uniform Duct with Uniform Mean Flow
247(3)
6.4.1 General Solution of the Convected Wave Equation
247(2)
6.4.2 Modal Wave Transfer Matrix
249(1)
6.5 Hard-Walled Ducts with Uniform Mean Flow
250(18)
6.5.1 Eigenvalues and the Orthogonality of Eigenfunctions
251(1)
6.5.2 Propagating and Evanescent Modes
252(1)
6.5.3 Modal Propagation Angles
253(2)
6.5.4 Transverse Modes of Common Duct Sections
255(1)
6.5.4.1 Rectangular Ducts
255(2)
6.5.4.2 Hollow Circular Ducts
257(3)
6.5.4.3 Annular Circular Ducts
260(1)
6.5.4.4 Spinning Modes
261(2)
6.5.5 Numerical Determination of Transverse Duct Modes
263(2)
6.5.6 Time-Averaged Acoustic Power
265(3)
6.6 Hard-Walled Uniform Ducts Packed with Porous Material
268(1)
6.7 Lined Uniform Ducts with Uniform Mean Flow
269(18)
6.7.1 Dispersion Equation for Uniformly Lined Circular Ducts
270(1)
6.7.1.1 Hard-Liner Solution for Hollow Ducts
270(2)
6.7.1.2 Iterative Graphical Solution
272(1)
6.7.2 Dispersion Equations for Uniformly Lined Rectangular Ducts
273(3)
6.7.3 Discussion of Transverse Modes
276(2)
6.7.3.1 Surface Modes
278(1)
6.7.3.2 Orthogonolity of Modes
279(1)
6.7.4 Liner Optimization
280(2)
6.7.5 Multi-Modal Attenuation Characteristics
282(3)
6.7.6 Non-Uniformly Lined Ducts
285(2)
6.8 Uniform Ducts with Sheared Mean Flow
287(7)
6.8.1 Solution of the Pridmore-Brown Equation
288(2)
6.8.2 Effect of the Mean Boundary Layer Thickness
290(4)
6.9 Ducts with Axially Non-Uniform Cross-Sectional Area
294(5)
6.10 Circularly Curved Ducts
299(13)
6.10.1 Rectangular Ducts
303(6)
6.10.2 Numerical Determination of Angular Wavenumbers
309(1)
6.10.3 Fundamental-Mode Approximation
310(2)
6.11 Uniform Ducts with Mean Swirl
312(4)
6.12 Ducts with Mean Temperature Gradient
316(6)
6.12.1 Ducts without Mean Flow
317(4)
6.12.2 Effect of Mean Flow
321(1)
References
322(4)
7 Transmission Of Wave Modes In Coupled Ducts
326(43)
7.1 Introduction
326(1)
7.2 Weak Form of the Convected Wave Equation
327(1)
7.3 Ducts with Identical Sections
328(4)
7.4 Sudden Area Changes
332(8)
7.4.1 Open Sudden Expansion
333(2)
7.4.1.1 Closed Through-Flow Expansion
335(1)
7.4.1.2 Closed Flow-Reversing Expansion
336(1)
7.4.2 Sudden Area Contraction
337(1)
7.4.3 Open Area Change with Multiple Ducts
337(3)
7.5 Perforated Baffles
340(2)
7.6 Cavity Coupled with Multiple Ducts
342(5)
7.6.1 Closed Cavity Modes
343(1)
7.6.2 The Green Function of the Cavity
344(1)
7.6.3 Coupling the Cavity with Ducts
345(2)
7.7 Coupled Perforated Ducts
347(11)
7.7.1 Acoustic Field in a Duct with a Single Aperture
349(2)
7.7.2 Wave Transfer Across a Row of Apertures
351(4)
7.7.3 Dissipative Silencers
355(3)
7.7.4 Lined Ducts
358(1)
7.8 Contracted Models of Silencers
358(9)
7.8.1 Expansion Chamber with Offset Inlet and Outlet Ducts
359(2)
7.8.2 Expansion Chamber with Double Outlet
361(1)
7.8.3 Flow-Reversing Chamber
362(1)
7.8.4 Through-Flow Resonator and Muffler
363(2)
7.8.5 Three-Pass Muffler
365(2)
References
367(2)
8 Effects Of Viscosity And Thermal Conductivity
369(30)
8.1 Introduction
369(1)
8.2 Convected Wave Equation for a Viscothermal Fluid
370(2)
8.3 Low Reduced Frequency Theory
372(14)
8.3.1 Circular Hollow Ducts
373(2)
8.3.1.1 Hard-Walled Ducts
375(2)
8.3.1.2 Wide-Duct Approximation
377(2)
8.3.1.3 Effect of Parabolic Mean Flow Velocity Profile
379(1)
8.3.1.4 Effect of Turbulent Boundary Layer
380(1)
8.3.2 Circular Annular Ducts
381(2)
8.3.3 Rectangular Ducts
383(3)
8.4 Time-Averaged Acoustic Power
386(2)
8.5 Sudden Area Changes and Junctions
388(4)
8.6 Coupled Narrow Ducts with Porous Walls
392(5)
References
397(2)
9 Reflection And Radiation At Open Duct Terminations
399(39)
9.1 Introduction
399(1)
9.2 Reflection Matrix and End-Correction
400(1)
9.3 Flanged and Unflanged Open Terminations without Mean Flow
401(7)
9.3.1 Exterior Surface Helmholtz Equation
401(1)
9.3.2 Flanged Open End
402(2)
9.3.2.1 Circular Ducts
404(2)
9.3.3 Unflanged Open End
406(2)
9.4 Reflection Matrix at an Unflanged Open End with Mean Flow
408(11)
9.4.1 The Exhaust Problem
408(3)
9.4.2 Circular Duct
411(3)
9.4.2.1 Plane-Wave Reflection Coefficient
414(2)
9.4.2.2 Reflection of Higher-Order Incident Modes
416(1)
9.4.3 Reflection at Flow Intakes
417(1)
9.4.3.1 Plane-Wave Reflection Coefficient
418(1)
9.5 Acoustic Radiation from Open Ends of Ducts
419(16)
9.5.1 Modal Radiation Transfer Function
419(1)
9.5.2 Radiated Acoustic Power
419(2)
9.5.3 Flanged Open End without Mean Flow
421(1)
9.5.3.1 Circular Ducts
422(2)
9.5.3.2 Rectangular Ducts
424(2)
9.5.4 Unflanged Circular Open End without Mean Flow
426(1)
9.5.5 Radiation from Unflanged Circular Open End with Mean Flow
427(2)
9.5.6 Simple-Source Approximation
429(2)
9.5.6.1 Effect of Vorticity
431(1)
9.5.7 Power Source Model
432(1)
9.5.8 Effect of Reflecting Surfaces
433(2)
References
435(3)
10 Modeling Of Ducted Acoustic Sources
438(36)
10.1 Introduction
438(2)
10.2 One-Port Sources Characterized by Unsteady Mass Injection
440(6)
10.3 Moving the Active Plane of One-Port Sources
446(5)
10.4 Two-Port Sources Characterized by Fluctuating Force Application
451(8)
10.4.1 Flow Noise
457(2)
10.5 Two-Port Sources Characterized by Ducted Combustion
459(10)
10.5.1 Combustion Oscillations and Instability
463(6)
10.6 Moving Source Planes of Two-Port Sources
469(1)
10.7 Ducted Loudspeakers
470(2)
References
472(2)
11 Radiated Sound Pressure Prediction
474(27)
11.1 Introduction
474(1)
11.2 Calculation of Sound Pressure Field of Ducted Sources
474(9)
11.2.1 Ducted One-Port Sources
476(2)
11.2.1.1 One-Dimensional Sources
478(2)
11.2.2 Ducted Two-Port Sources
480(2)
11.2.3 Multiple Radiating Outlets
482(1)
11.3 Analysis of Sound Pressure
483(4)
11.4 Insertion Loss
487(4)
11.4.1 Noise Reduction
488(2)
11.4.2 Attenuation
490(1)
11.5 Multi-Modal Transmission Loss Calculations
491(3)
11.6 In-Duct Sources Characterized by Acoustic Power
494(6)
11.6.1 The ASHRAE Method
497(3)
References
500(1)
12 Measurement Methods
501(32)
12.1 Introduction
501(1)
12.2 Measurement of In-Duct Acoustic Field
501(9)
12.2.1 Multi-Modal Wave Field Decomposition
502(1)
12.2.2 The Two-Microphone Method
503(2)
12.2.2.1 Calibration of Microphones
505(2)
12.2.2.2 Signal Enhancement
507(1)
12.2.3 Measurement of the Plane-Wave Reflection Coefficient
507(1)
12.2.4 Measurement of Wavenumbers
508(2)
12.3 Measurement of Passive Acoustic Two-Ports
510(4)
12.3.1 Basics of the Four Microphone Method
510(1)
12.3.2 Measurement of Attenuation
511(1)
12.3.3 Measurement of Transmission Loss
512(1)
12.3.4 Measurement of the Wave Transfer Matrix
512(2)
12.4 Measurement of One-Port Source Characteristics
514(16)
12.4.1 The Two-Load Method
516(1)
12.4.1.1 Implementation with Non-Calibrated Loads
516(1)
12.4.1.2 Implementation with Calibrated Loads
517(1)
12.4.2 Geometrical Interpretation of the Two-load Method
517(1)
12.4.3 The Apollonian Circle of Two Loads
518(2)
12.4.3.1 Upper and Lower Bounds for Source Pressure Strength
520(2)
12.4.4 Calculation Bounds to Sound Pressure
522(1)
12.4.5 The Three-Load Method
523(1)
12.4.6 Over-Determined Methods
524(1)
12.4.6.1 Over-Determined Two-Load Method
525(1)
12.4.6.2 Over-Determined Three-Load Method
525(1)
12.4.7 The Fuzzy Two-Load Method
526(1)
12.4.8 The Explicit N-Load Method
527(3)
12.5 Measurement of Two-Port Source Characteristics
530(1)
References
530(3)
13 System Search And Optimization
533(19)
13.1 Introduction
533(1)
13.2 Direct Random Search
534(5)
13.3 Interval Analysis
539(1)
13.4 The Inverse Method
540(11)
13.4.1 Acoustic Path Space
540(3)
13.4.2 Acoustic Path Space on the Attenuation Plane
543(3)
13.4.3 Signature of Acoustic Paths
546(2)
13.4.4 System Search in Acoustic Path Space
548(1)
13.4.5 Acoustic Path Spaces for Different Targets
549(1)
13.4.5.1 Noise Reduction
549(1)
13.4.5.2 Insertion Loss
550(1)
References
551(1)
Appendix A Basic Equations of Fluid Motion
552(9)
A.1 Integral Forms of Conservation Laws
552(3)
A.1.1 Conservation of Mass
553(1)
A.1.2 Conservation of Momentum
553(1)
A.1.3 Conservation of Energy
554(1)
A.2 State Equations and the Speed of Sound
555(1)
A.3 Equations of Motion of Ideal Fluids
556(2)
A.3.1 Continuity Equation
556(1)
A.3.2 Momentum Equation
557(1)
A.3.3 Energy Equation
557(1)
A.4 Equation of Motion of Newtonian Fluids
558(2)
A.4.1 Momentum Equation
558(1)
A.4.2 Energy Equation
559(1)
References
560(1)
Appendix B Acoustic Properties of Rigid-Frame Fibrous Materials 561(4)
References 565(2)
Appendix C Impedance of Compact Apertures 567(1)
C.1 Empirical and Semi-Empirical Models 567(4)
C.2 Theoretical Models 571(6)
References 577(2)
Index 579
Erkan Dokumac is Professor Emeritus of Mechanical Engineering at Dokuz Eylül University (zmir, Turkey). He is currently on the Editorial Advisory Board for the Journal of Sound and Vibration and is the author of software used for acoustic design of mufflers and silencers, as well as many scientific papers on duct acoustics.
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