Broadband Sound Absorption of Subwavelength Porous Meta-Liner

This work proposes a subwavelength porous meta-liner with broadband sound absorption from 900 to 1,200 Hz. The meta-liner consists of four subunits, which are made up of porous material and hollow coiling slit embedded in it. Each subunit is designed by adjusting the length of its coiling slit to achieve resonance in the target frequency and examined by the finite element method (FEM). These subunits are arranged in an axial direction uniformly and radial direction periodically to propose a meta-liner duct. Then, the noise reduction of the propeller system with the meta-liner duct is measured by the microphone array. The result shows that the propeller with the meta-liner duct can reduce the noise level of the ducted propeller between 3.6 and 5.5 dB in the design frequency range, which also effectively reduces the noise level in the broadband frequency range. Therefore, the meta-liner shows a good application prospect in the noise reduction of the propeller.