Abstract
Noise attenuation performance of embankment was investigated by numerical analysis using the finite difference time domain (FDTD) method. The visualization of transient sound propagation over embankments has revealed that the sound wave travels along their shoulder slopes. From the quantitative examination on the insertion loss, it has been found that the noise attenuation effects in low frequencies become lower as the shoulder slope of the embankment becomes gentler. Even if the embankment has finite acoustic impedance (in many cases, embankments are covered with lawn or grass), it is considered that the deterioration of noise attenuation effect in low frequencies remains because the acoustic impedance is generally large. When assessing their noise reduction effects, such deterioration of the performance must be carefully considered.
