Enhancement of low and medium frequency sound absorption using fabrics and air gaps

Porous acoustic materials are among the most frequently employed acoustic materials. This paper evaluates the acoustic performance of porous materials concerning the addition of how the fabric layout and addition of an air gap influence sound absorption coefficient at low and medium frequencies. The acoustic measurements were performed on multilayers of woven fabrics formed from different weave structures and nonwoven fabrics using an impedance tube. The result indicates that due to the different geometrical structures of woven fabric and the layout designs of multilayer fabrics, significant improvements were observed in sound absorption performance at the frequency range from 160 Hz to 3150 Hz. The air gap with a multilayer of porous material enhanced low to medium-frequency sound absorption. Furthermore, the physical fabric properties analysis of porosity using X-ray tomography indicates that the surface of a single layer of plain fabric structures is more porous than that of sateen, rib, and twill woven fabrics. The correlation between the air permeability and sound absorption coefficient (& alpha;) results indicates an inverse relationship for multilayer porous fabrics.