Characterizing the Relationship between Microstructural and Acoustic Properties of Open-Celled Metal Foams

Open-celled metal foams are lightweight, porous metals whose physical structure is completely defined by their pore size, relative density, and the base material from which they are made. Thus, they can be engineered for maximizing noise reduction by designing their structural parameters to allow broadband noise absorption. Here, we present preliminary results from our work on characterizing the effect of each microstructural parameter on the acoustic properties of metal foams. Metal foam samples with individually controlled pore size, relative density, and base material were fabricated and tested using a four-microphone normal impedance tube setup. The obtained results were studied for parametric trends. The experimental results are compared with numerical results obtained by using measured transport properties as inputs for the Johnson-Champoux-Allard equivalent fluid model as well as the poroelastic Biot-Allard model. The numerical results are verified with the physical tests and the relation between a metal foam's structural parameters and its acoustic properties is demonstrated.