Double Spiral Meta-Sus Silencer for Broadband Noise Reduction

Acoustic metamaterials have emerged as an innovative solution to noise challenges across various industries. In this paper, we present our broadband effective Meta-Sus silencers, which can be fabricated from virtually any material while maintaining consistent performance. The double spiral design allows each spiral to be tuned to a specific frequency range of 1 to 1.5 octaves, and when combined, the system achieves an average insertion loss (IL) or transmission loss (TL) of over 20 dB across 3 to 4 octaves. We utilized finite element modeling (FEM) for simulating the silencers and conducted an 11-parameter genetic optimization to develop silencers with outer diameters of 100, 150, and 200 mm. Multiple design iterations and optimizations were carried out for each diameter, considering varying effective frequencies, performance envelopes, and opening ratios. Over 30 silencers were manufactured using SLS and FDM 3D printing techniques, and were experimentally tested. Insertion loss tests were conducted with an impedance tube setup, where the silencers were exposed to air at the termination side (without airflow). Pressure drop measurements were performed using a modified wind tunnel setup for each sample. Finally, four samples underwent testing under flow conditions according to the ISO 7235 standard.