Predicting Outdoor Sound

Cover
Half Title
Title Page
Copyright Page
Table of Contents
Preface
Authors’ Biographies
Chapter 1: Introduction
	1.1 Early Observations
	1.2 A Brief Survey of Outdoor Sound Attenuation Mechanisms
	1.3 Data Illustrating Ground Effect
		1.3.1 Propagation from a Fixed Jet Engine Source
		1.3.2 Propagation over Discontinuous Ground
	1.4 Data Illustrating the Combined Effects of Ground and Meteorology
		1.4.1 More Fixed Jet Engine Data
		1.4.2 Road Traffic Noise Propagation over Flat Terrain under Strong Temperature Inversion
		1.4.3 Meteorological Effects on Railway Noise Propagation over Flat Terrain
		1.4.4 Road Traffic Noise Propagation in a Valley
	1.5 Classification of Meteorological Conditions for Outdoor Sound Prediction
	1.6 Typical Sound Speed Profiles
	1.7 Linear-Logarithmic Representations of Sound Speed Profiles
	1.8 Air Absorption
	Note
	References
Chapter 2: The Propagation of Sound near Ground Surfaces in a Homogeneous Medium
	2.1 Introduction
	2.2 A Point Source Above Smooth Flat Acoustically Soft Ground
	2.3 The Sound Field Above a Locally Reacting Ground
	2.4 The Sound Field Above a Layered Extended-Reaction Ground
	2.5 Surface Waves Above Porous Ground
	2.6 Experimental Data and Numerical Predictions
	2.7 The Sound Field Due to a Line Source Near the Ground
	References
Chapter 3: Predicting Effects of Source Characteristics
	3.1 Introduction
	3.2 Sound Fields Due to Dipole Sources Near the Ground
		3.2.1 The Horizontal Dipole
		3.2.2 The Vertical Dipole
		3.2.3 An Arbitrarily Orientated Dipole
	3.3 The Sound Field due to an Arbitrarily Orientated Quadrupole
	3.4 Railway Noise Directivity and Prediction
	3.5 Source Characteristics of Road Traffic
		3.5.1 Basic Formulae and Parameters
		3.5.2 Directivity Corrections
		3.5.3 Other Corrections and Limitations
	3.6 Source Characteristics of Wind Turbines
		3.6.1 Sound-generation Mechanisms
		3.6.2 Typical Spectra of Large Horizontal Axis Wind Turbines
		3.6.3 Horizontal and Vertical Directivity
		3.6.4 Amplitude Modulation
	References
Chapter 4: Numerical Methods Based on Time-Domain Approaches
	4.1 Introduction
	4.2 An Efficient Complete Finite-Difference Time-Domain Model for Outdoor Sound Propagation
		4.2.1 Sound Propagation Equations
		4.2.2 Numerical Discretization
			4.2.2.1 Homogeneous and Still Propagation Medium
			4.2.2.2 Inhomogeneous Media
			4.2.2.3 Moving Medium
				4.2.2.3.1 Staggered-in-time
				4.2.2.3.2 Collocated-in-time
				4.2.2.3.3 Prediction-Step Staggered-In-time
			4.2.2.4 Numerical Accuracy and Stability
		4.2.3 Modelling Propagation in a Moving Unbounded Atmosphere
		4.2.4 Modelling Finite Impedance Boundary Conditions
			4.2.4.1 Impedance Plane Approach
			4.2.4.2 Ground Interaction Modelling by Including a Layer of Soil
				4.2.4.2.1 Poro-Rigid Frame Model
				4.2.4.2.2 Poro-Elastic Frame Models
	4.3 Long-Distance Sound Propagation Prediction Based on FDTD
		4.3.1 Moving Frame FDTD
		4.3.2 Hybrid Modelling: Combining FDTD with GFPE
			4.3.2.1 Advantages of the GFPE Method
			4.3.2.2 Complex Source Region, Simplified Receiver Region
			4.3.2.3 Procedure for One-way Coupling from FDTD to GFPE
			4.3.2.4 Numerical Example
			4.3.2.5 Computational Cost Reduction
	References
Chapter 5: Predicting the Acoustical Properties of Ground Surfaces
	5.1 Introduction
	5.2 Predicting Ground Impedance
		5.2.1 Empirical and Phenomenological Models
		5.2.2 Microstructural Models Using Idealized Pore Shapes
		5.2.3 Approximate Models for High Flow Resistivities
		5.2.4 Relaxation Models
		5.2.5 Relative Influence of Microstructural Parameters
	5.3 Physical Inadmissibility of Semi-Empirical Models
	5.4 Predicting Effects of Surface Roughness
		5.4.1 Boss and Stochastic Models
		5.4.2 Impedance Models Including Rough Surface Effects
			5.4.2.1 Hard Rough Surfaces
			5.4.2.2 Rough Finite Impedance Surfaces
			5.4.2.3 Modified ‘Boss’ and Empirical Models for Regularly Spaced Roughness Elements
			5.4.2.4 Multiple Scattering Models
			5.4.2.5 A Roughness Spectrum Model
		5.4.3 Propagation over Rough Seas
			5.4.3.1 Effective Impedance of Rough Sea Surfaces
			5.4.3.2 Predicted Propagation of Offshore Piling Noise
			5.4.3.3 Predicted Rough Sea Effects on Sonic Booms
	5.5 Predicting Effects of Ground Elasticity
		5.5.1 Coupling from Airborne Sound to Structures and Ground Vibration
		5.5.2 Biot-Stoll Theory
		5.5.3 Numerical Calculations of Acoustic–Seismic Coupling
			5.5.3.1 Fast Field Program for Layered Air-Ground Systems (FFLAGS)
			5.5.3.2 Example Predictions of Low-Frequency Effects
	References
Chapter 6: Measurements of the Acoustical Properties of Ground Surfaces and Comparisons with Models
	6.1 Impedance Measurement Methods
		6.1.1 Impedance Tube
		6.1.2 Impedance Meter
		6.1.3 Non-Invasive Measurements
			6.1.3.1 Direct Measurement of Reflection Coefficient
			6.1.3.2 Impedance Deduction from Short-Range Measurements
			6.1.3.3 Model Parameter Deduction from Short-Range Propagation Data
			6.1.3.4 A Template Method for Impedance Deduction
			6.1.3.5 Effective Flow Resistivity Classification
			6.1.3.6 Direct Impedance Deduction
	6.2 Comparisons of Impedance Spectra with Model Predictions
	6.3 Fits to Short-Range Propagation Data Using Impedance Models
		6.3.1 Short-Range Grassland Data and Fits
		6.3.2 Fits to Data Obtained over Forest Floors, Gravel and Porous Asphalt
		6.3.3 Railway Ballast
		6.3.4 Measured Flow Resistivities and Porosities
		6.3.5 Comparison of Template and Direct Deduction Methods over Grassland
	6.4 Spatial and Seasonal Variations in Grassland Impedance
		6.4.1 Predicted Effects of Spatial Variation
		6.4.2 Measured Effects of Varying Moisture Content
		6.4.3 Influence of Water Content on ‘Fast’ and Shear Wave Speeds
		6.4.4 Measured Spatial and Seasonal Variations
	6.5 Ground Effect Predictions based on Fits to Short-Range Level Difference Spectra
	6.6 On the Choice of Ground Impedance Models for Outdoor Sound Prediction
	6.7 Measured and Predicted Surface Roughness Effects
		6.7.1 Roughness-Induced Ground Effect
		6.7.2 Excess Attenuation Spectra for Random and Periodic Roughness
		6.7.3 Roughness-Induced Surface Waves
		6.7.4 Outdoor Measurements of the Influence of Roughness on Ground Effect
	6.8 Measured and Predicted Effects of Ground Elasticity
		6.8.1 Elasticity Effects on Surface Impedance
		6.8.2 Ground Vibrations Due to Airborne Explosions
	6.9 Non-Linear Interaction with Porous Ground
	6.10 Deduction of Soil Properties from Measurements of A/S Coupling
	References
Chapter 7: Influence of Source Motion on Ground Effect and Diffraction
	7.1 Introduction
	7.2 A Monopole Source Moving at Constant Speed and Height Above a Ground Surface
	7.3 The Sound Field of a Source Moving with Arbitrary Velocity
	7.4 Comparison with Heuristic Calculations
	7.5 Point Source Moving at Constant Speed and Height Parallel to a Rigid Wedge
		7.5.1 Kinematics
		7.5.2 Diffracted Pressure for a Source in Uniform Motion
	7.6 Source Moving Parallel to a Ground Discontinuity
		7.6.1 Introduction
		7.6.2 Uniform Motion Parallel to a Single Discontinuity
	7.7 Source Moving at Constant Height Parallel to a Rigid Barrier Above the Ground
		7.7.1 Barrier over Hard Ground
		7.7.2 Barrier over Impedance Ground
	7.8 Source Moving over Externally Reacting Ground
	References
Chapter 8: Predicting Effects of Mixed Impedance Ground
	8.1 Introduction
	8.2 Single Impedance Discontinuity
		8.2.1 De Jong’s Semi-Empirical Method
		8.2.2 Modified De Jong Method
		8.2.3 Rasmussen’s Method
	8.3 Multiple Impedance Discontinuities
		8.3.1 An Extended De Jong Method
		8.3.2 The nMID (Multiple Impedance Discontinuities) Method
		8.3.3 Nyberg’s Method
		8.3.4 Fresnel-zone Methods
		8.3.5 The Boundary Element Method
	8.4 Comparisons of Predictions with Data
		8.4.1 Single Impedance Discontinuity
		8.4.2 Impedance Strips
	8.5 Refraction above Mixed Impedance Ground
	8.6 Predicting Effects of Ground Treatments near Surface Transport
		8.6.1 Roads
			8.6.1.1 Sound Propagation from a Road over Discontinuous Impedance
			8.6.1.2 Predicted Effects of Replacing ‘Hard’ by ‘Soft’ Ground Near a Road
			8.6.1.3 Predicting Effects of Low Parallel Walls and Lattices
		8.6.2 Tramways
		8.6.3 Railways
			8.6.3.1 Porous Sleepers and Porous Slab Track
	8.7 Predicting Meteorological Effects on the Insertion Loss of Low Parallel Walls
		8.7.1 Configuration and Geometry
		8.7.2 Numerical Methods
		8.7.3 Meteorological Effects
	8.8 Predicting Effects of Variability in Downward-Refraction and Ground Impedance
		8.8.1 Introduction
		8.8.2 Meteorological Data and Processing
		8.8.3 Grassland Impedance Data
		8.8.4 Sound Propagation Modelling and Numerical Parameters
		8.8.5 Detailed Analysis of a Temporal Sequence
		8.8.6 Statistical Analysis of Temporal Variation over a Full Year
			8.8.6.1 Spectral Variation
			8.8.6.2 Variation in A-Weighted Pink Noise
			8.8.6.3 Convergence to Yearly L Aeq
			8.8.6.4 Conclusions
	References
Chapter 9: Predicting the Performance of Outdoor Noise Barriers
	9.1 Introduction
	9.2 Analytical Solutions for the Diffraction of Sound by a Barrier
		9.2.1 Formulation of the Problem
		9.2.2 The MacDonald Solution
		9.2.3 The Hadden and Pierce Solution for a Wedge
		9.2.4 Approximate Analytical Formulation
	9.3 Empirical Formulations for Studying the Shielding Effect of Barriers
	9.4 The Sound Attenuation by a Thin Plane on the Ground
	9.5 Noise Reduction by a Finite-Length Barrier
	9.6 Adverse Effect of Gaps in Barriers
	9.7 The Acoustic Performance of an Absorptive Screen
	9.8 Gabion Barriers
		9.8.1 Numerical Predictions of Comparative Acoustical Performance
		9.8.2 Laboratory Measurements on Porous-Stone Gabions
		9.8.3 Outdoor Measurements on a Gabion Barrier
		9.8.4 Optimizing Gabion Barriers for Noise Reduction
	9.9 Other Factors in Barrier Performance
		9.9.1 Barrier Shape
		9.9.2 Meteorological Effects on Barrier Performance
		9.9.3 Rough and Soft Berms
		9.9.4 Berms vs Barriers in Wind
	9.10 Sonic Crystal Noise Barriers
	9.11 Predicted Effects of Spectral Variations in Train Noise During Pass-by
	References
Chapter 10: Predicting Effects of Vegetation, Trees and Turbulence
	10.1 Measured Effects of Vegetation
		10.1.1 Influence of Vegetation on Soil Properties
		10.1.2 Measurements of Sound Transmission through Vegetation
		10.1.3 Measured Attenuation due to Trees, Shrubs and Hedges
	10.2 Predicting Sound Transmission through Vegetation
		10.2.1 Ground Effect with Plants and Vegetation
		10.2.2 Models for Foliage Effects
			10.2.2.1 Empirical Models
			10.2.2.2 Scattering Models
		10.2.3 Reduction of Coherence by Scattering
		10.2.4 Predictions of Ground Effect, Scattering and Foliage Attenuation
			10.2.4.1 Sound Propagation in Crops
			10.2.4.2 Sound Propagation in Forests
	10.3 Influence of Ground on Propagation Through Arrays of Vertical Cylinders
		10.3.1 Laboratory Data Combining ‘Sonic Crystal’ and Ground Effects
		10.3.2 Numerical Design of Tree Belts for Traffic Noise Reduction
		10.3.3 Measured and Predicted Effects of Irregular Spacing in the Laboratory
	10.4 Reflection from Forest Edges
	10.5 Meteorological Effects on Sound Transmission Through Trees
	10.6 Combined Effects OF Trees, Barriers and Meteorology
	10.7 Turbulence and its Effects
		10.7.1 Turbulence Mechanisms
		10.7.2 Models for Turbulence Spectra
		10.7.3 Clifford and Lataitis Prediction of Ground Effect in Turbulent Conditions
		10.7.4 Ostashev et al. Improvements on the Clifford and Lataitis Approach
		10.7.5 Height Dependence of Turbulence
		10.7.6 Turbulence-Induced Phase and Log-Amplitude Fluctuations
		10.7.7 Scattering by Turbulence
		10.7.8 Decrease in Sound Levels due to Turbulence
		10.7.9 Measurement of Turbulence
		10.7.10 Inclusion of Atmospheric Turbulence in the Fast Field Program
		10.7.11 Comparisons with Experimental Data
		10.7.12 Including Turbulence in FDTD Calculations
	10.8 Equivalence of Turbulence and Scattering Influences on Coherence
	References
Chapter 11: Ray Tracing, Analytical and Semi-empirical Approximations for A-Weighted Levels
	11.1 Ray Tracing
	11.2 Linear Sound Speed Gradients and Weak Refraction
	11.3 Approximations for A-Weighted Levels and Ground Effect Optimization in the Presence of Weak Refraction and Turbulence
		11.3.1 Ground Effect Optimization
		11.3.2 Integral Expressions for A-Weighted Mean Square Sound Pressure
		11.3.3 Approximate Models for Ground Impedance
		11.3.4 Effects of Weak Refraction
		11.3.5 Approximations for Excess Attenuation
			11.3.5.1 Variable Porosity or Thin Layer Ground
			11.3.5.2 Rough Ground
			11.3.5.3 Smooth High Flow Resistivity Ground
		11.3.6 Numerical Examples and Discussion
			11.3.6.1 Comparison with Data: Avon Jet Engine Source
			11.3.6.2 Sensitivity to Spectrum, Source Height and Distance
			11.3.6.3 Variation with Distance
			11.3.6.4 Effects of Refraction
		11.3.7 Concluding Remarks
	11.4 A Semi-Empirical Model for A-Weighted Sound Levels at Long Range
	References
Chapter 12: Engineering Models
	12.1 Introduction
	12.2 ISO 9613–2
		12.2.1 Description
		12.2.2 Basic Equations
			12.2.2.1 Geometrical Divergence
			12.2.2.2 Atmospheric Absorption
			12.2.2.3 Ground Effect
			12.2.2.4 Screening
			12.2.2.5 Meteorological Correction
		12.2.3 General Critique
		12.2.4 Accuracy of ISO 9613-2 Ground Effect
	12.3 CONCAWE
		12.3.1 Introduction
		12.3.2 Basis and Provisions of Scheme
		12.3.3 Criticisms of CONCAWE
	12.4 Calculation of Road Traffic Noise (CRTN)
		12.4.1 Introduction
		12.4.2 Basic Equations
			12.4.2.1 L 10 Levels
			12.4.2.2 Corrections for Mean Traffic Speed, Percentage of Heavy Vehicles and Gradient
			12.4.2.3 Correction for Type of Road Surface
			12.4.2.4 Distance Correction
			12.4.2.5 Ground Cover Correction
			12.4.2.6 Screening Correction
			12.4.2.7 Site Layout
			12.4.2.8 Segments and Road Junctions
	12.5 Calculation of Railway Noise (CRN)
	12.6 NORD2000
	12.7 HARMONOISE
		12.7.1 Introduction and Background
		12.7.2 General Methodology
			12.7.2.1 Basic Equations
			12.7.2.2 Identification of Propagation Planes
			12.7.2.3 Recommended Numerical Techniques
			12.7.2.4 Meteorological Conditions
			12.7.2.5 Frequency Resolution
			12.7.2.6 Long-term Integrated Levels
			12.7.2.7 Validation
		12.7.3 Analytical Point-to-point Model
			12.7.3.1 Introduction
			12.7.3.2 Methodology for Combining Ground and Barrier Effect
			12.7.3.3 Ground Reflection Model
			12.7.3.4 Sound Diffraction Model
				12.7.3.4.1 Single Diffraction
				12.7.3.4.2 Multiple Diffractions
			12.7.3.5 Transition Model
			12.7.3.6 Refraction
			12.7.3.7 Coherence Losses
			12.7.3.8 Scattering by Turbulence
	12.8 The Environmental Noise Directive (END) Scheme (CNOSSOS-EU)
		12.8.1 Ground Effect
		12.8.2 Criticisms
	12.9 Performance of Railway Noise Prediction Schemes in High-Rise Cities
	12.10 Performance of Engineering Models in a Complex Road Traffic Noise Example
		12.10.1 Site and Models
		12.10.2 Approximating the Berm Slope
		12.10.3 Road Traffic Source Power Modelling
		12.10.4 Daytime vs Nighttime Measurements and Predictions
		12.10.5 Model Performance
	12.11 Predicting Wind Turbine Noise
		12.11.1 An Untypical Industrial Source
		12.11.2 Complex Meteorologically Induced Propagation Effects
		12.11.3 Ground Effect for Wind Turbine Sound Propagation
		12.11.4 Propagation over Non-Flat Terrain
	12.12 Prediction Requirements for Outdoor Sound Auralization
		12.12.1 Introduction
		12.12.2 Simulating Outdoor Attenuation by Filters
		12.12.3 Auralization of a Noise Abatement Based on a Priori Recordings
	References
Index
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