Design of periodic foam structures for acoustic applications: Concept, parametric study and experimental validation

Reticulated foams are widely used in noise control applications. However, difficulties in controlling the foaming process makes it difficult to control the microstructure and consequently the absorption characteristics of stochastic foams. Present work is a step toward designing an appropriate microstructure of foam to obtain desired acoustics performance using the concept of periodic foams. Periodic foam structures are created from designed unit cells by uniform spatial repetition of the unit cell in the three-dimensional domain. Three different unit cell configurations are created, characterized and compared using the Johnson-Champoux and Allard OCA) model. These three unit cell configurations are further used to create periodic foam structures and prototypes of those structures are fabricated using additive manufacturing techniques. The measured characteristic impedance, complex wave propagation constant, absorption coefficient, and transmission loss for the fabricated samples arc in close agreement with the JCA model predictions. Designed periodic foam structures proposed in this study offer a novel way to tailor the absorption spectrum to specifications in noise control and other acoustics applications. (C) 2019 The Authors. Published by Elsevier Ltd.