Low Frequency Noise Attenuation inside Ducts using locally resonant periodic flush mounted Steel Patches

Traditional passive noise control techniques using Helmholtz resonators have size limitations at low frequency due to the long wavelengths. Promising noise reductions, with flush mounted Stainless Steel patches with no such constraints can be obtained building on local resonance phenomenon implemented in acoustic metamaterials techniques. The objective of the current paper is to introduce locally resonant thin Steel patches flush mounted to an acoustic duct walls aiming at creating frequency stop bands at the low frequency zone (below 1 KHz). Green’s Function is used under the framework of interface response theory to predict the degree of attenuation of the local resonant patches. The experimental results were compared with Analytical theory and Finite elements and a close agreement was found.