Environmental and sound divergence effects on the performance of rectangular sonic crystals with Helmholtz resonators

摘要

Environmental and sound divergence effects on the noise attenuation performance of rectangular sonic crystals with Helmholtz resonators were investigated using experimental methods. The experiments were conducted under indoor, semi-indoor, and outdoor conditions. The positions of the noise source and receiver were rotated to different angles to study the sound divergence effects on the sonic crystals. For a full array of sonic crystals, performance of the sonic crystals at indoor and semi-indoor were similar and poorer than outdoor at all frequencies. The presence of Helmholtz resonators caused a significant amount of insertion loss at 1000Hz for experiments that were indoors and outdoors. 1000Hz was the designed resonant frequency produced by the Helmholtz resonators. The reduction of the number of columns of the sonic crystals resulted in greater negative insertion loss in all three environment conditions. The sound divergence effects on the sonic crystals were greater for frequencies above 800 Hz and they were less significant for frequencies below 800 Hz. The types of noises had noticeable effects on insertion loss obtained by the sonic crystals. Numerical simulations were performed to investigate the dispersion properties of the sonic crystals. Numerical results with and without Helmholtz resonators generally showed similar trends with the corresponding experimental results.