This study presents the design, fabrication, and acoustic evaluation of eco-friendly sandwich composites integrating 3D-printed micro-perforated panels (MPPs) with natural fiber core layers. MPPs, produced from Polylactic Acid (PLA) and Thermoplastic Polyurethane (TPU) via fused deposition modeling, were manufactured with varying hole diameters (1.0 mm, 1.3 mm), center-to-center spacings (3.0 mm, 5.0 mm), and thicknesses (0.5 mm, 1.5 mm). Hemp and waste wool fibers were used as core layers. The effects of structural and material parameters on the sound absorption coefficient (SAC), noise reduction coefficient (NRC), NRC-modified values, and sound absorption average (SAA) were evaluated through a systematic experimental investigation. The findings showed that sandwich composites with a waste wool core and TPU panels exhibited superior acoustic performance, with optimal MPP designs identified as 1.3 mm diameter and 1.5 mm thickness, combined with 3.0 mm spacing for wideband absorption and 5.0 mm spacing for targeted low-frequency absorption. Statistical analysis confirmed that hole diameter, hole spacing, panel thickness and material selection had a significant impact on acoustic performance. These results were theoretically validated through an theoretical modeling approach. The findings highlighted the potential of using 3D printing and natural fibers to create sustainable sandwich structures with optimal acoustic performance, offering a practical design framework for tailoring panel configurations to target frequency ranges and enabling eco-friendly, high-performance noise control solutions in architectural, transportation, and industrial applications.
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