Broadband sound absorption using multiple slow waves in metaporous layers, by Joong Seok Lee (Chungnam National University)

DENORMS Action’s Workshop “Modelling of high performance acoustic structures Porous media, metamaterials and sonic crystals”, Rome, 24-25th January 2017

Website of DENORMS Action

Programme of the Workshop

Acoustic metamaterials (i.e. subwavelength absorbers), metasurfaces and sonic crystals for audible sound manipulation

Speaker: Joong Seok Lee (Chungnam National University)

Abstract: 

Broadband sound absorption is still challenging even with various acoustic metamaterials being developed. Recently, we proposed an acoustic metamaterial designed with a porous layer, or a metaporous layer, to broaden the frequency band for effective sound absorption by elaborately using multiple slow waves and combining local and global resonance phenomena. The proposed metaporous layer consists of a hard-backed porous layer of a finite thickness inside which a set of rigid partitions of varying lengths is inserted. The mechanism of the broadband sound absorption of the metaporous layer is analyzed by using an effective medium approach. This work shows that the enhanced sound absorption capability at the low-frequency range of the band is mainly due to the formation of global resonances caused by multiple slow waves over the thickness of the metaporous layer. The enhancement at the high-frequency range is attributed to the combined effects of the global resonances and the local resonances directly related to the sizes of inserted partitions.