Numerical modelling of the sound absorption spectra for bottleneck dominated porous metallic structures

Numerical simulations are used to test the ability of several common equivalent fluid models to predict the sound absorption behaviour in porous metals with “bottleneck” type structures. Of these models, Wilson’s relaxation model was found to be an excellent and overall best fit for multiple sources of experimental acoustic absorption data. Simulations, incorporating Wilson’s model, were used to highlight the relative importance of key geometrical features of bottleneck structures on the normal incidence sound absorption spectrum. Simulations revealed significant improvements in absorption behaviour would be achieved, over a “benchmark” structure from the literature, by maximising the porosity (0.8) and targeting a permeability in the range of 4.0 × 10−10 m2. Such a modelling approach should provide a valuable tool in the optimisation of sound absorption performance and structural integrity, to meet application-specific requirements, for a genre of porous materials that offer a unique combination of acoustic absorption and load bearing capability.