Acoustical Absorptive Properties of Nonwovens

Abstract

Today much importance is given to the acoustical environment. Noise control and its principles play an important role in creating an acoustically pleasing environment. This can be achieved when the intensity of sound is brought down to a level that is not harmful to human ears. Achieving a pleasing environment can be obtained by using various techniques that employ different materials. One such technique is by absorbing the sound and converting it to thermal energy. Fibrous, porous and other kinds of materials have been widely accepted as sound absorptive materials. A literature scan [19, 20, 53, 76] showed nonwovens could be considered to be a prospective candidate for sound absorption. The impetus for this study stemmed from the drawbacks associated with the existing sound absorbing materials like felts made from glass, asbestos and rock wool and foams. Some of these drawbacks include the fact that the materials are unsuitable for molding, non-recyclable, difficult to handle and install, dust accumulating and in the case of foams are high in density.

These drawbacks are forcing the acoustical product manufacturers to look into natural, biodegradable raw materials. To assist in that effort, the research presented here studies the feasibility of using kenaf fibers blended with reclaim polyester fibers and other fiber blends as sound absorptive materials. Products from kenaf/reclaim fiber blends will have the benefit of low raw materials and manufacturing cost, at the same time providing a suitable end use for reclaim polyester fibers.

Early work in noise control has shown the importance of understanding micro- structural and other physical parameters in designing high performance acoustic materials. As a final objective, this research describes how the physical elements of nonwoven sound absorbent system like fiber type, fiber size, fiber cross section, material thickness, density, airflow resistance and porosity can change the absorption behavior of nonwovens. Influence of fire retardant treatment, surface impedance, air gap, compression, manufacturing methods and attachment of film on sound absorption behavior of nonwovens were also considered.