Interior noise reduction remains a critical challenge for the automotive industry, as excessive cabin noise can reduce driving comfort and contribute to fatigue and long-term hearing issues. Among the various noise sources, low-frequency booming noise, caused by the coupling between structural and acoustic cavity modes, has the most significant impact on passenger perception. This study investigates the dominant booming frequencies in a gasoline vehicle and identifies that the principal resonance range occurs between 140 and 250 Hz. To address this issue, a set of thin labyrinthine acoustic metamaterials is proposed for integration into the ethylene propylene diene monomer (EPDM) firewall layer. Ten metamaterial configurations were designed to target the identified frequency range, and their sound absorption coefficients and sound transmission loss characteristics were derived experimentally using an impedance tube. The performance of these metamaterials was further evaluated through vehicle-scale numerical modeling, followed by comparison with road test data. The results demonstrate that several configurations, particularly the cellular and hexagonal designs, provide substantial low-frequency attenuation, outperforming the conventional EPDM absorber and offering a promising lightweight solution for future automotive noise control applications.
Dalvand et al. (Mon,) studied this question.