Master Thesis: Silent Silhouettes

2025/09/14

The free DDU Master’s thesis “Silent Silhouettes” by Stefanie Appelgrün investigates the potential of additively manufacturing acoustic absorbers from clay. The goal is to develop a mono-material, sustainable, and acoustically effective structure that does not require additional carrier materials or composites. As part of an extensive initial research, the current state of research on additively manufactured clay structures, the acoustic behavior of porous materials, and the influence of internal geometry on sound absorption was analyzed. Building on this, the first part of the project identified geometric parameters that enhance the acoustic performance of clay structures — among them a wave-shaped outer contour, a microstructured surface with openings, and an internal, highly porous geometry based on a growth-based algorithm. Differential growth generates channel-like geometries that, through specific overlaps, form complex three-dimensional pore spaces. The developed geometry is based on alternating concave and convex base curves that create a pocket-like structure arranged bead-like along a higher-order curve. This results in a silhouette with narrow vertical openings that enables targeted reflection and attenuation of sound down to the energetic minimum. At defined points, the sound is absorbed by the porous growth pattern developed here. Computer-based simulations, impedance tube measurements, and reverberation chamber tests confirm the increased acoustic performance. This demonstrates the potential of additively manufactured clay structures as a sustainable alternative to conventional acoustic solutions.