Directional quantification of power dissipation in sound-absorbing metaporous layers

Abstract

Metaporous layers composed of finite-length porous layers with rigid inclusions embedded have recently received much attention given their ability to greatly enhance sound absorption. Compared with homogeneous porous layers, the insertion of rigid inclusions into porous layers can lead to a significant enhancement in the sound-absorbing performance. It is because the resulting inhomogeneity in metaporous layers generates multidirectional effects to dissipate the sound power, which may not be observed in homogeneous porous layers. This implies that directional evaluations of sound power dissipation in metaporous layers can be important for better designs that yield further enhancements of the sound-absorbing performance. In most previous works related to metaporous layers, unfortunately, quantitative studies of the directional characteristics of sound power dissipation inside of the layers are relatively rare. In this work, we investigate the directional effect of rigid inclusions on the dissipation of sound power in metaporous layers quantitatively. By spatially decomposing the dissipated power in orthogonal directions, the directional characteristics of sound power dissipation are evaluated along the thickness and lateral directions of hard-backed metaporous layers. The present directional quantification provides greater insight for those attempting to interpret the performance capabilities of metaporous layers and can be applied as well to the creation of optimal designs for these types of layers.