Sound absorption properties of thermally bonded nonwovens based on composing fibers and production parameters

This article reviews the noise absorption capacity of thermally bonded nonwovens in the range of audible frequencies (125-2500 Hz). First, we focus on the effects of the properties of the fibers, which constitute nonwovens, on the sound absorption properties, and then we consider the web orientation angle of nonwovens. We also investigate a composite model of the sound absorption properties of nonwovens, including the surface roughness and panel vibration. We have used an impedance tube interferometer, which provides the normal incidence sound absorption coefficient of materials, for the determination of the noise absorption properties of nonwovens produced under different conditions. The noise absorption capacity of nonwovens depends primarily on the thickness and surface characteristics of specimens, but the effects of the fiber contents are only marginal. Interestingly, when there is a panel in front of nonwovens, the noise absorption capacity increases significantly at low and medium frequencies (250-1000 Hz). (C) 2004 Wiley Periodicals, Inc.