Effects of Total Surface Area and Fabric Density on the Acoustical Behavior of Needlepunched Nonwoven Fabrics

Abstract

Nonwoven fabrics are ideal materials for use as acoustical insulation products because they have high total surface. The surface area of the fabric is directly related to the denier and cross-sectional shape of the fibers in the fabric. Smaller deniers yield more fibers per unit weight of the material, higher total fiber surface area and greater possibilities for a sound wave to interact with the fibers in the structure. Another important parameter is the packing density of the fibers in the nonwoven material. More fibers per unit volume at the same fabric thickness yield greater possibilities for sound waves to interact with the fibers. Fabric density also affects the geometry and the volume of the voids in the fabric structure. Acoustical properties of fabric materials are measured by one of two methods: the impedance tube method (ASTM C 384-98) and the acoustical chamber method. The impedance tube method uses very small test samples. Large reverberation rooms and large test samples are used for the acoustic chamber method. A direct comparative acoustical properties measurement device has been developed and fabricated at Clemson University School of Materials Science and Engineering. This paper provides a description of the measurement devices and acoustical measurement data for needlepunched nonwoven fabrics made from three different polyester fiber shapes and two denier levels.