| 摘要 |
PROBLEM TO BE SOLVED: To realize an estimation method having sufficient prediction accuracy, by repeating reflections under a condition that an incidence angle and a reflection angle of a sound velocity at a reflection boundary element are equal to each other, and obtaining a total acoustic energy amount of the sound velocity reaching the boundary element including a reflection sound prediction point set on a model after the reflections are attenuated. SOLUTION: In a two-dimensional road sectional model constituted of a viaduct girder 1, a right and a left sound-shutting walls 2, 2 and a road face 3, a noise prediction point O is set while line sound source S1 , S2 are set to vehicles of upper and lower lanes. Sound is treated geometrically acoustically. A sound at a sound source position set at a (k)th time is displayed in vector form and a vector quantity D is obtained as a sound velocity. In order to obtain a reflection influence coefficientηat the noise prediction point O, acoustic energies of the sound velocity D reaching a sound detection boundary elementΩD' are sequentially added, and an accumulated total energy is obtained. A noise energy of the sound velocity consumed at a reflection boundary elementΩD of a propagation model is directly calculated in the same manner. The reflection influence coefficientηis obtained from both energies.
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