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Description
Road noise transmitted through vehicle door structures remains a critical challenge in automotive noise, vibration, and harshness (NVH) performance, particularly in the low-frequency range below 1 kHz. This study presents a mass-producible acoustic metamaterial designed for integration into automotive door trims to reduce structure-borne sound transmission without increasing weight or manufacturing complexity.The proposed design consists of a single-material, periodically patterned plate fabricated using a one-step molding process, ensuring compatibility with industrial production. The periodic protrusion geometry is designed to induce a flexural wave bandgap in the sub-1000 Hz range, targeting the dominant frequency components of road noise. Dispersion analysis confirms the formation of a polarization-specific bandgap that suppresses out-of-plane wave propagation, which is the primary contributor to sound radiation.Experimental validation demonstrates that the molded metamaterial plate improves sound transmission loss (STL) by approximately 2 dB in the 400–800 Hz range compared to a flat plate of equivalent mass. When implemented in an automotive door trim, frequency response measurements show a reduction in vibro-acoustic transfer from the door to the cabin. Furthermore, on-road driving tests reveal a reduction in interior sound pressure levels by approximately 1.4 dB at 40 km/h, where road noise is dominant.These results demonstrate that simple, monolithically molded acoustic metamaterials can effectively enhance vibro-acoustic performance in practical vehicle applications. The proposed approach provides a scalable and cost-effective pathway for integrating metamaterial-based noise reduction into mass-produced automotive components.