Abstract
Acoustical insulation and absorption properties of nonwoven fabrics depend on fiber geometry and fiber arrangement within the fabric structure. The different structures of the fibers result in different total surface areas of nonwoven fabrics. Nonwoven fabrics such as vertically lapped fabrics are ideal materials for use as acoustical insulation products, because they have high total surface. Vertically lapped nonwoven technology consists of carding, perpendicular layering of the carded webs, and through-air bonding using synthetic binder fibers. 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 fabric structure.
The research in the literature uses two methods for measuring acoustical properties of fabric materials: the impedance tube and reverberation room method. Small test samples are in the impedance tube method and sound absorption coefficient is determined at each frequency. Large reverberation rooms and large test samples are used for the reverberation room method. A direct comparative acoustical properties measurement device that was designed and fabricated at Clemson University School of Materials Science & Engineering was used to measure acoustical insulation in this research. This paper provides a description of the measurement devices and acoustical measurement data for vertically lapped nonwoven fabrics made from three different polyester fiber shape and two denier levels.