Metaporous sound absorber with neck-embedded microslit resonators for thin porous materials with low flow resistivity

In this paper, we propose a metaporous absorber with air-filled resonators that enhances low-frequency sound absorption for thin porous materials with low flow resistivity and a simple theoretical model under the assumption of plane wave propagation inside the material. The metaporous absorber features a periodic array structure made up of unit cells, within which microslit resonators are strategically placed in the porous material. Three distinct unit cells, each exhibiting unique sound absorption characteristics, are proposed. Combining two of these unit cells makes it possible to offset the shortcomings of each other's sound absorption capabilities, resulting in a broader range of high-sound-absorption effects. Firstly, a transfer matrix modeling of the metaporous absorbers is proposed, numerically verified by the finite element method and experimentally validated by impedance tube measurement. Using the constructed transfer matrix model and genetic algorithm optimization, we designed two highly efficient near-perfect sound absorbers at frequencies from 700 Hz to 1.7 kHz and experimentally demonstrated their sound absorption characteristics. The present absorber is particularly effective for enhancing the performance of thin porous materials with lower flow resistivity.