Low‐Frequency Broadband Acoustic Metamaterial Based on Helmholtz Resonance and Layered Porous Substrates

In the field of highway noise control, acoustic metamaterials play a crucial role due to their exceptional capability for subwavelength manipulation of acoustic resonance. However, existing metamaterials are plagued by certain limitations, such as the inefficient utilization of resonant space and constraints on the design of feature sizes. Herein, an acoustic metamaterial consisting of Helmholtz resonators (TNHR‐PM) that integrate tapered necks and layered porous material substrates is proposed. Through the embedding of tapered neck configurations into resonant cavities and incorporation of layered porous damping media, synergistic effects between local resonance and material dissipation are established, significantly enhancing sound absorption performance and expanding design size range. The results show that TNHR‐PM achieves an outstanding absorption peak of 0.982 at 245 Hz while maintaining near‐perfect absorption ( α  ≥ 0.9) across a wide range of neck diameter and length parameters. Notably, a combination of merely six 50‐mm‐thick units enables broadband sound absorption from 285 to 488 Hz with an average absorption coefficient of 0.945. This study proposes an innovative strategy for developing acoustic metamaterials with excellent low‐frequency sound absorption.