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Conference Papers Year : 2014

Developing acoustically effective foams via cellular structure


This extended abstract illustrate results examining how, on two case studies, sound absorbing and sound insulating properties of a real foam sample can significantly be improved via cellular structure in the audible frequency range; yielding to an increase of the sound absorption in the middle frequency range, and an increment of the sound transmission loss of 2 dB from 0.5 to 10 kHz. Starting from typical poroelastic parameters of the foam, numerical experiments are leading to the definition of two different sets of poroelastic parameters at macro-scale which represent reachable near optimal targets for absorption and insulation noise treatments. From literature analysis and numerical homogenization techniques, three key levers were identified to translate the targeted set of poroelastic parameters into feasible cellular structures: i) a homothetic reduction of the cell size; ii) an increase in the closure rate of the membranes; iii) and a decrease in the Young's modulus of the base material. Experimental data of the foams as manufactured are shown to compare fairly well with computational results. Further recommendations are given to improve the design of the cellular lightweight structures. 1 Introduction The purpose of this extended abstract is to illustrate how novel procedures typically based on bottom-up approaches for microstructure optimization of sound proofing materials [1, 2] can readily serve as a support to the development of acoustically effective foams in an industrial context. This applied acoustics work in noise control engineering adds to the knowledge basis by linking effective sets of poroelastic parameters to morphological data at the pore size level that help to develop innovative foams. Two case studies are discussed through typical sound absorption and insulation problems, giving examples that could help others deal with similar cases. The main insights resulting from this applied work are essentially twofold. (i) A required increase in both resistivity and tortuosity identified at macro-scale for improving significantly the middle frequency sound absorption performance of standard foam can be achieved through membrane effects. (ii) A required increase in resistivity is obtainable thanks to a homothetic reduction of the size of open-cell foam, and can also be achieved through membrane effect. Its combination with a reduction of the skeleton's Young modulus-chemically tuned by the number of urethane bounds-lead to a + 2 dB insertion loss performance in the [500 Hz-10 kHz] frequency range, when compared to the same initial standard foam. 2 Cellular structures recommendations
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hal-01163940 , version 1 (15-06-2015)


  • HAL Id : hal-01163940 , version 1


A. Duval, V. Marcel, M. T. Hoang, Camille Perrot. Developing acoustically effective foams via cellular structure. Symposium on the Acoustics of Poro-Elastic Materials (SAPEM 2014), Dec 2014, Stockholm, Sweden. ⟨hal-01163940⟩
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