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.
Nie et al. (Mon,) studied this question.