Broadband low-frequency ventilated acoustic metamaterial using decorated membrane-integrated Helmholtz resonator

Abstract

Ventilated acoustic metamaterials are critical for balancing noise control and airflow in engineering systems, but traditional designs are plagued by narrow bandwidth and bulky structures when targeting low-frequency noise. Herein, we propose a compact ventilated acoustic metamaterial unit that integrates a Helmholtz resonator (HR) with a decorated membrane resonator (denoted as HRDMR hereinafter). This structure introduces a novel coupling mechanism between a HR and a mass-loaded, tension-insensitive membrane, leveraging the synergistic resonance between cavity air and decorated membrane vibration to achieve broadband low-frequency sound insulation while maintaining unobstructed airflow. Finite element simulations and transmission loss tube experiments demonstrate that a 5-unit cascaded HRDMR array features an ultra-compact size exhibiting sub-wavelength dimensions (λ/16 at 500 Hz) and achieves a sound transmission loss exceeding 10 dB over the frequency range of 489–1058 Hz. Compared to traditional HRs, this design achieves an approximately 20% bandwidth expansion. Furthermore, this design exhibits robust parameter stability, retaining performance across its operating band even when the Young modulus of the membrane varies within 14–20 MPa (a 30% variation). This work provides a high-performance and ultra-compact solution for low-frequency noise insulation in ventilation ducts, vehicle cabins, and other airflow-dependent engineering applications.