Omnidirectional acoustic absorber with a porous core - theory and measurements Free

An omni-directional acoustic absorber consisting of a porous core and the impedance matching metamaterial layer has been designed and tested in the laboratory. Semi-analytical and numerical models have been developed and validated. The numerical model takes into account the viscous losses in the matching layer. A 1.5 metre demonstrator has been built and tested under acoustic and weak shock excitation. Testing with acoustic excitation showed good agreement between measurement and model, with near perfect absorption between 400 and 1000Hz. The findings suggest that structure is equally effective when wrapped around an object like a column, pipeline or the underside of a vehicle, as it would be when entirely filled with an absorbing porous material.