Preparation and characterization of gradient compressed porous metal for high-effciency and thin-thickness acoustic absorber

Abstract

Increasing absorption effciency and decreasing total thickness of the acoustic absorber is favorable to promote its practical application. Four compressed porous metals with compression ratios of 0%, 30%, 60%, and 90% were prepared to assemble the four-layer gradient compressed porous metals, which aimed to develop the acoustic absorber with high-effciency and thin thickness. Through deriving structural parameters of thickness, porosity, and static flow resistivity for the compressed porous metals, theoretical models of sound absorption coeffcients of the gradient compressed porous metals were constructed through transfer matrix method according to the Johnson-Champoux-Allard model. Sound absorption coeffcients of four-layer gradient compressed porous metals with the different permutations were theoretically analyzed and experimentally measured, and the optimal average sound absorption coeffcient of 60.33% in 100-6000 Hz was obtained with the total thickness of 11 mm. Sound absorption coeffcients of the optimal gradient compressed porous metal were further compared with those of the simple superposed compressed porous metal, which proved that the former could obtain higher absorption effciency with thinner thickness and fewer materials. These phenomena were explored by morphology characterizations. The developed high-effciency and thin-thickness acoustic absorber of gradient compressed porous metal can be applied in acoustic environmental detection and industrial noise reduction.