Coupled integral equations for sound propagation above a hard ground surface with trench cuttings

2006 ◽  
Vol 120 (3) ◽  
pp. 1209-1216 ◽  
Author(s):  
Gong Li Wang ◽  
Weng Cho Chew ◽  
Michael J. White
Keyword(s):  
Integral Equations ◽  
Sound Propagation ◽  
Ground Surface

NUMERICAL PREDICTIONS OF SOUND PROPAGATION FROM A CUTTING OVER A ROAD-SIDE NOISE BARRIER

2005 ◽  
Vol 13 (01) ◽  
pp. 145-162 ◽  
Author(s):  
ANDREW T. PEPLOW
Keyword(s):  
Integral Equations ◽  
Sound Propagation ◽  
Boundary Integral Equations ◽  
Traffic Noise ◽  
Noise Spectrum ◽  
Boundary Integral ◽  
Impedance Boundary ◽  
Numerical Predictions ◽  
Simple Boundary ◽  
Noise Barrier

A boundary integral equation is described for the prediction of acoustic propagation from a monofrequency coherent line source in a cutting with impedance boundary conditions onto surrounding flat impedance ground. The problem is stated as a boundary value problem for the Helmholtz equation and is subsequently reformulated as a system of boundary integral equations via Green's theorem. The numerical solution of the coupled boundary integral equations by a simple boundary element method is then described. Predictions of A-weighted insertion losses for a traffic noise spectrum are made illustrating the effects of depth of the cutting and the profile of the associated noise barrier.

scholarly journals Infrasound propagation in the Arctic

2021 ◽  
Author(s):  
D. Wilson ◽  
Vladimir Ostashev ◽  
Michael Shaw ◽  
Michael Muhlestein ◽  
John Weatherly ◽  
...  
Keyword(s):  
Sound Propagation ◽  
Ground Surface ◽  
Polar Vortex ◽  
Basic Research ◽  
Arctic Region ◽  
Initial Step ◽  
The Arctic ◽  
Equation Modeling ◽  
Katabatic Wind ◽  
Long Distance

This report summarizes results of the basic research project “Infrasound Propagation in the Arctic.” The scientific objective of this project was to provide a baseline understanding of the characteristic horizontal propagation distances, frequency dependencies, and conditions leading to enhanced propagation of infrasound in the Arctic region. The approach emphasized theory and numerical modeling as an initial step toward improving understanding of the basic phenomenology, and thus lay the foundation for productive experiments in the future. The modeling approach combined mesoscale numerical weather forecasts from the Polar Weather Research and Forecasting model with advanced acoustic propagation calculations. The project produced significant advances with regard to parabolic equation modeling of sound propagation in a windy atmosphere. For the polar low, interesting interactions with the stratosphere were found, which could possibly be used to provide early warning of strong stratospheric warming events (i.e., the polar vortex). The katabatic wind resulted in a very strong low-level duct, which, when combined with a highly reflective icy ground surface, leads to efficient long-distance propagation. This information is useful in devising strategies for positioning sensors to monitor environmental phenomena and human activities.

A study on variations in excess attenuation due to ground surface and meteorological conditions based on a long-term outdoor sound propagation experiment

2021 ◽  
Vol 263 (2) ◽  
pp. 4368-4375
Author(s):  
Takatoshi Yokota ◽  
Koichi Makino ◽  
Genki Iizumi ◽  
Takuya Tsutsumi
Keyword(s):  
Sound Propagation ◽  
Meteorological Data ◽  
Surface Condition ◽  
Ground Surface ◽  
Prediction Method ◽  
Meteorological Condition ◽  
Pulse Method ◽  
Meteorological Conditions ◽  
Ground Condition ◽  
Excess Attenuation

From the winter of 2018, outdoor sound propagation experiments (maximum horizontal range: 300 m) have been repeatedly conducted three times a day on weekdays at a glider airfield in Hokkaido, Japan. The ground condition of the experimental field is grass-covered in summer and snow-covered in winter. In each experiment, impulse responses have been measured by time-stretched pulse method and excess attenuation has been obtained at receiving points. Meteorological data at the field has been also measured. Based on the data of excess attenuation collected under various meteorological conditions over a long period, variation in sound propagation characteristics due to the differences in ground surface condition and meteorological condition has been investigated. The numerical analysis based on the GFPE method has been also carried out with changing the parameter of meteorological condition and ground surface condition. By comparing the results with the experimental data, the prediction method of the variations in excess attenuation has been also investigated.

A comparison of the ground excess attenuation model in Harmonoise with finite-difference time-domain solutions under grounds with mixed types

2021 ◽  
Vol 263 (1) ◽  
pp. 5584-5594
Author(s):  
Yusaku Koshiba ◽  
Takuya Oshima
Keyword(s):  
Finite Difference ◽  
Numerical Method ◽  
Time Domain ◽  
Finite Difference Time Domain ◽  
Sound Propagation ◽  
Ground Surface ◽  
Flow Resistivity ◽  
Mixed Types ◽  
Difference Time ◽  
Excess Attenuation

Total noise exposure is calculated for the evaluation of health effects caused by environmental noise. For the calculation, computationally drawn noise maps are used. In the computation process, sound propagation over ground surface with mixed types should be calculated for better accuracy. One engineering model that allows such calculation is the ground excess attenuation model of the Harmonoise model. However, the applicability of the model to such complex grounds remains unclear. In this study, a 40m-length ground surface with a discontinuity in flow resistivity is defined. By moving the discontinuity position, sound propagation from a point source and a receiver at each end is calculated using the model and a numerical method. The numerical method is the finite-difference time-domain method with porous medium modeling that has been proven to be accurate. It is found from the numerical results that in higher frequencies the excess attenuations in terms of the discontinuity position have fluctuations. The fluctuations are found to correspond to the interference by diffraction path difference passing the discontinuity. In contrast, the model results exhibit smooth transition from an extremity of single flow resistivity surface to another. A simple model of such diffraction needs to be developed.

FORWARD AND BACKWARD MODAL STATISTICS FOR ROUGH SEABED SURFACE SCATTERING IN SHALLOW WATER

2014 ◽  
Vol 22 (01) ◽  
pp. 1440004 ◽  
Author(s):  
D. P. KNOBLES ◽  
J. D. SAGERS
Keyword(s):  
Shallow Water ◽  
Integral Equations ◽  
Rough Surface ◽  
Numerical Solutions ◽  
Sound Propagation ◽  
Surface Scattering ◽  
Coupled Equations ◽  
Random Rough Surface ◽  
Basic Characteristics

Addressed is the physics of sound propagation through a shallow water waveguide whose seabed has a random rough surface. The basic coupled integral equations for the modal amplitudes can be split into forward and backward going coupled integral equations. Numerical solutions of the coupled equations are obtained for multiple roughness realizations from which ensemble averages can be obtained for the modal intensities and cross-mode coherence as a function of range. Sample calculations illustrate some of the basic characteristics of the average cross-mode coherence and intensity with and without seabed attenuation and for different source depths on range scales of 1500 acoustic wavelengths.

INTEGRAL EQUATION COUPLED MODE APPROACH APPLIED TO INTERNAL WAVE PROBLEMS

2001 ◽  
Vol 09 (01) ◽  
pp. 149-167 ◽  
Author(s):  
D. P. KNOBLES ◽  
S. A. STOTTS ◽  
R. A. KOCH ◽  
T. UDAGAWA
Keyword(s):  
Integral Equation ◽  
Internal Wave ◽  
Integral Equations ◽  
Sound Propagation ◽  
Integral Equation Method ◽  
Coupled Equations ◽  
Coupled Mode ◽  
Energy Conserving ◽  
Linear Internal Wave ◽  
Wave Problems

A two-way coupled mode approach based on an integral equation formalism is applied to sound propagation through internal wave fields defined at the 1999 Shallow Water Acoustics Modeling Workshop. Solutions of the coupled equations are obtained using a powerful approach originally introduced in nuclear theory and also used to solve simple nonseparable problems in underwater acoustics. The basic integral equations are slightly modified to permit a Lanczos expansion to form a solution. The solution of the original set of integral equations is then easily recovered from the solution of the modified equations. Two important aspects of the integral equation method are revealed. First, the Lanczos expansion converges faster than a Born expansion of the original integral equations. Second, even when the Born expansion diverges due to strong mode coupling, the Lanczos expansion converges. It is shown that the internal wave problems examined are essentially one-way propagation problems because one observes good agreement between the coupled mode solutions and those provided by an energy-conserving parabolic equation algorithm. In the Workshop examples, at both 25 and 250 Hz, significantly greater coupling between modes occurs in the linear internal wave field case than the nonlinear soliton case.

Integral equations and sound propagation in a shallow sea

2004 ◽  
Vol 40 (9) ◽  
pp. 1330-1344 ◽  
Author(s):  
I. K. Lifanov ◽  
S. L. Stavtsev
Keyword(s):  
Integral Equations ◽  
Sound Propagation ◽  
Shallow Sea
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