Sound propagation around arrays of rigid and porous cylinders in free space and near a ground boundary

Sound propagation through sonic crystals has been widely studied both theoretically and experimentally, because of its potential applications in many areas such as environmental noise barriers and sound cloaking. In this paper, a finite-difference time-domain (FDTD) numerical simulation coupled with the immersed boundary method is used to investigate the transmission properties of sonic crystals modeled as arrays of cylinders. Arrays in free field as well as those arranged above a ground boundary are studied. In the latter case, the cylinder axes are parallel to the ground plane. By comparing with the semi-analytical solutions, the numerical scheme is validated for simple arrays of rigid cylinders. The effects of locations and materials of cylinders, along with the ground effect, are investigated. The results are presented with discussions on achieving optimized sonic crystals for sound blockage.