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Abstract:
The purpose of this work is to check if additive manufacturing technologies are suitable for reproducing porous samples designed for sound absorption. The work is an inter-laboratory test, in which the production of samples and their acoustic measurements are carried out independently by different laboratories, sharing only the same geometry codes describing agreed periodic cellular designs. Different additive manufacturing technologies and equipment are used to make samples. Although most of the results obtained from measurements performed on samples with the same cellular design are very close, it is shown that some discrepancies are due to shape and surface imperfections, or microporosity, induced by the manufacturing process. The proposed periodic cellular designs can be easily reproduced and are suitable for further benchmarking of additive manufacturing techniques for rapid prototyping of acoustic materials and metamaterials.

Keywords:
porous materials, designed periodicity, additive manufacturing, sound absorption

Abstract:
With a rapid development of modern Additive Manufacturing Technologies it seems inevitable that they will sooner or later serve for production of specific porous and meta-porous acoustic treatments. Moreover, these new technologies are already being used to manufacture original micro-geometric designs of sound absorbing media in order to test microstructure-based effects, models and hypothesis. In the view of these statements, this work reports differences in acoustic absorption measured for porous specimens which were produced from the same CAD-geometry model using several additive manufacturing technologies and 3D-printers. A specific periodic unit cell of open porosity was designed for the purpose. The samples were measured acoustically in the impedance tube and also subjected to a thorough microscopic survey in order to check their quality and look for the discrepancy reasons.

Keywords:
Sound absorption, Additive Manufacturing Technologies