Gypsum-based sound absorber produced by 3D printing technology

The paper presents an alternative gypsum-based porous cellular sound absorber manufactured using 3D printing technology. The effects of cell structure and porosity on sound absorption coefficient have been experimentally investigated for the designed gypsum-based porous metamaterials. In addition to this, the numerical acoustic analyses were also performed to predict sound absorption behaviour of the produced gypsum-based porous metamaterials. Furthermore, the numerical flow analyses were also carried out to gain insight into the basic parameters such as flow resistance and tortuosity that affect the sound absorption behaviour of the designed gypsum-based porous metamaterials. As a result of the experimental and numerical studies, it has been observed that the gypsum specimens produced in porous structure provide a significant sound absorption in comparison to non-porous reference specimen. It has been also noticed that the open-cell gypsum specimens, in which the cells are interaction with each other, are much more efficient in terms of sound absorption than the open-cell structure in which there is no direct interaction between the cells. In addition to this, it was found that the gypsum specimens having Octet unit-cell structure have the highest sound absorption performance in the open cell structures. In other respects, it was also found that the sound absorption behaviour of each unit cell structure is getting worse with the increasing porosity. The numerical flow analyses have indicated that increase in porosity reduces the flow resistance and tortuosity levels of the open unit-cell structures and consequently worsens the sound absorption behaviour. (C) 2019 Elsevier Ltd. All rights reserved.