Time-domain simulations of sound propagation near a ground surface in comparison with the ANSI impedance measurement models

2019 ◽  
Vol 145 (3) ◽  
pp. 1781-1781
Author(s):  
Z. C. Zheng ◽  
Junjian Zhang ◽  
Guoyi Ke
Keyword(s):  
Time Domain ◽  
Sound Propagation ◽  
Ground Surface ◽  
Impedance Measurement ◽  
Measurement Models

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.

Time-domain calculation of sound propagation in lined ducts with sheared flows

AIAA Journal ◽  
2000 ◽  
Vol 38 ◽  
pp. 768-773 ◽  
Author(s):  
Yusuf Ozyoruk ◽  
Lyle N. Long
Keyword(s):  
Time Domain ◽  
Sound Propagation ◽  
Sheared Flows ◽  
Lined Ducts

High Amplitude Sound Propagation at Low Frequencies in a Flow Duct Lined With Resonators: A Time Domain Solution

1988 ◽  
Vol 110 (4) ◽  
pp. 545-551 ◽  
Author(s):  
A. Cummings ◽  
I.-J. Chang
Keyword(s):  
Time Domain ◽  
Internal Combustion Engines ◽  
Sound Propagation ◽  
Sound Field ◽  
High Amplitude ◽  
Combustion Engines ◽  
Low Frequencies ◽  
The Time Domain ◽  
Flow Duct ◽  
Good Agreement

A quasi one-dimensional analysis of sound transmission in a flow duct lined with an array of nonlinear resonators is described. The solution to the equations describing the sound field and the hydrodynamic flow in the neighborhood of the resonator orifices is performed numerically in the time domain, with the object of properly accounting for the nonlinear interaction between the acoustic field and the resonators. Experimental data are compared to numerical computations in the time domain and generally very good agreement is noted. The method described here may readily be extended for use in the design of exhaust mufflers for internal combustion engines.

scholarly journals Study Effect of Objects Orientation in the Mediums On GPR Signal Reflections Using FDTD Simulation

2018 ◽  
Vol 3 (11) ◽  
pp. 73-77
Author(s):  
Aye Mint Mohamed Mostapha ◽  
Gamil Alsharahi ◽  
Abdellah Driouach
Keyword(s):  
Finite Difference ◽  
Time Domain ◽  
Ground Penetrating Radar ◽  
High Frequency ◽  
Electromagnetic Waves ◽  
Ground Surface ◽  
Propagation Path ◽  
Fdtd Simulation ◽  
Ground Penetrating ◽  
Dielectric Objects

Ground penetrating radar (GPR) is a very effective tool for detecting and identifying objects below the ground surface.  based on  the propagation and reflection of high-frequency electromagnetic waves. The GPR reflection can be affected by many things like the type of objects orientation, their shapes ..ect. The purpose of this paper is to  study by simulation the effect of objects orientation in two different mediums (dry and wet sand) on the GPR signal reflection using Reflexw software which is based on a numerical method known as finite difference in time domain (FDTD).  The simulations that have been realized included a conductor  and dielectric objects. The results obtained have led us to find that the propagation path, the reflection strength and the signal form change with the change of object orientation and nature. To confirm the validity of the results, we compared them with experimental results previously published by researchers under the same conditions.

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