Abstract
The propagation characteristics of road traffic noise from an embankment road are investigated through three-dimensional wave-based numerical analysis. Since this is a large-scale problem, we use the fast multipole boundary element method (FMBEM) as a highly efficient wave-based numerical method. We analyze sound fields around embankments with various slope angles and clarify that the sound pressure gradient changes with the slope angle, and in particular, the sound pressure level (SPL) distribution changes significantly near the line where the embankment slope meets the ground surface. When the prediction plane is an orthogonal cross-section to the direction of the lane, the distribution of the difference in A-weighted SPL between the case where the embankment is sloped and the case where it has a right angle is generally similar regardless of the position of the prediction plane. Based on this result, we propose an empirical formula to express the difference between the case with a slope and the case with a right angle. We confirm that the proposed formula provides a certain level of accuracy regardless of the location of the prediction plane when we appropriately determine the coefficients in the formula for each case from the viewpoint of error minimization.
Published Version
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