Acoustical performance of additively manufactured metamaterials: sound absorption and transmission loss

Additive manufacturing facilitates the creation of complex acoustic metamaterial geometries that are unattainable through traditional processes. In this study, the sound-absorption and transmission-loss characteristics of three cylindrical architectures—a solid reference, a honeycomb lattice, and a Schwarz-P minimal-surface design—were assessed at fixed outer dimensions after fabrication by fused-deposition modelling in polylactic acid (PLA) and thermoplastic polyurethane (TPU). Normal-incidence absorption was measured in an impedance tube (ISO 10534-2), and transmission loss was measured using the four-microphone, two-load method (ASTM E2611) within the plane-wave band; a finite-element model implemented in COMSOL Multiphysics was used to interpret trends and enable like-for-like comparisons. The solid specimen exhibited high but narrowband absorption with limited insulation; the Schwarz-P provided broadband absorption with a nearly flat, moderate TL; and the honeycomb showed modest absorption, yet the highest broadband TL experimentally. These results indicate that internal topology and base polymer provide complementary control of bandwidth and magnitude at constant size, supporting rapid screening of geometry/material options for compact noise-control applications under normal incidence. Future work will extend the fixed-footprint matrix to graded or hybrid designs and targeted parametric variations, and will broaden the metrological scope beyond the tube band where appropriate.