Investigation of sound absorption behavior of porous gypsum structures produced by binder jetting technique

Noise control is one of the most important problems faced in the interior space analyses for the places like malls, houses, hospitals and factories in which there are dense human crowds. In designing these kinds of crowded spaces, using sound-absorbing materials in order to decrease the background noises which reduce the acoustic quality is one of the most frequently used methods. In this study it will be focused on an alternative sound-absorbing structure for crowded interior space activities by investigating sound absorption potential of gypsum materials which have various cell structures. Sound-absorbing behaviours of closed-cell and open-cell-structured gypsum materials (BCC, Gyroid and Octet) produced through binder jetting technique which is one of the additive manufacturing methods have been experimentally examined and the effects of cell structure, porosity and thickness on sound absorption coefficient have been presented. With the aim of predicting the sound-absorbing behaviours of porous gypsum structures and of leading the experimental studies to be conducted, numerical analyses have been made. Besides, in order to have an opinion about basic parameters such as flow resistance and tortuosity, numerical flow analyses for open-cell structures have been made. As a result of the experiments carried out and the numerical analyses made, it has been seen that the gypsum samples produced in porous structures, in comparison to non-porous reference sample, provided a substantial sound absorption. Also, it has been observed that open-cell gypsum samples are much more efficient in terms of sound absorption and among the open-cell structures, Octet unit cell structured gypsum samples have the highest sound-absorbing capacity. It has been detected that in each of the samples who have BCC, Gyroid and Octet unit cell structures, sound absorption behavior was deteriorated with the increase in porosity. As a result of the numerical flow analyses, it has been observed that the main reason for that was the decrease in the flow resistance of cell structures and in tortuosity due to the increase in porosity. Lastly, it has been observed that in BCC, Gyroid and Octet unit cell structures, increase in thickness causes sound absorption coefficient - frequency curve to shift to low frequencies and the maximum sound absorption coefficient value occurs at lower frequencies.