Sound absorption using sonic crystals with coupled Helmholtz resonators

Sonic crystals are made up of a periodic arrangement of sound scatterers and absorbers that exhibit band-gap behaviour, allowing them to block out certain band of frequencies of sound (Bragg's law). This allows artificially engineered structures, through proper design of geometry and placements of scatterers, to achieve specific acoustic properties for sound absorption and noise mitigation. Embedding Helmholtz resonators into sonic crystals have been shown to improve the low-frequency attenuation performance as a combined system. In this study, we investigated the interaction of coupled Helmholtz resonators within a sonic crystal. Parametric studies were conducted using the finite element method on the spectral insertion loss of these sonic crystals with various arrangements of the Helmholtz resonators. The results show that sharp attenuation at specific frequencies may be achieved by proper tuning of these resonators, improving the low-frequency performance of the sonic crystals as a broadband sound absorber.