Broadband ventilated metamaterial absorber from non-local coupling

Due to its role in broadband impedance matching and acoustic modulations, the non-local couplings in acoustic metamaterials have received considerable attention recently. In previous research, there has been established a trade-off between absorption performance and geometric thickness. However, broadband absorption of sound energy under ventilation conditions with non-local couplings are yet explored. Here, we demonstrate unconventional double Helmholtz resonators with embedded apertures to achieve broadband absorption under a ventilated environment, whose absorption efficiency is robust to the change of ventilation ratio. Besides, different broadband working frequency ranges can be achieved by modulating the non-local coupling in different opening directions. Hence, our work provides a potential and promising method for attenuating broadband sound energy at low frequencies under various ventilation scenarios.