Broadband acoustic absorbers based on double split-ring resonators at deep subwavelength scale

We report both experimentally and numerically that a low-frequency acoustic absorber is realized by double split-ring resonators backed with rigid wall. This leverages the impedance matching dissipation effect, which arises due to thermal-viscous loss within dual channels. As result, this achieves near-perfect sound absorption (the coefficient α = 0.99) at subwavelength thickness of around λ/23. By assembling six unit cells distinct structure parameters form supercell, fractional bandwidth ratio center frequency) increased 40% an average 0.86. Acoustic experiment results validate exceptional performance, also in agreement simulation results. Moreover, employing we create anechoic room demonstrating broadband wide range incident angles while occupying significantly less space than traditional sound-absorbing porous materials. Our composite design paves way for absorbers deep scale