Utilization of air-gap to improve the acoustic absorption of coir fiber

Abstract

The aim of this paper is to improve the coir fiber acoustical properties with air gap layers. Analyses were based on Allard elastic model with transfer matrix analysis. Results were close to experimental values and predicted the path and resonances very well. Further analyses derived that having a fiber layer backed by an air gap was better than leaving the same gap in between that layer. In the later arrangement, the sound field impacted a porous layer with low thickness and bulk density. It was concluded that other acoustic absorption techniques such as adding perforated plate may be combined with coir fiber-air gap structure to improve the low frequency acoustic absorption coefficient without any need to highly increase the air gap thickness.