Heavy vehicle noise control by parallel barrier

This paper presents numerical and experimental investigations on the noise control of heavy vehicles by means of a pair of parallel barriers. Heavy vehicles (trucks and buses) are significant contributors to overall traffic noise levels. A two-point source is used to simulate the sound generated by the heavy vehicles. A primary source at ground level and a secondary source at a higher position are considered. For the purpose of attenuating noise levels at both sides of the road, two identical barriers with finite length are erected in parallel above the ground. The fast multipole boundary element method (FMBEM) is then developed to evaluate the insertion loss (IL) of the parallel barriers. The Burton–Miller method is adopted to avoid the fictitious eigenfrequencies when using the BEM for exterior acoustic problems. To calculate the sound field accurately, robustly and efficiently in the whole frequency range, the plane wave expansion and partial wave expansion are combined together to form the wideband FMBEM. Indoor scale-model experiments are conducted and compared with the numerical calculations by the FMBEM. Roughly speaking, numerical predictions agree with the experimental measurements.