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Acoustical Properties of Nonwoven Fabrics

E.A. Vaughn, R.J. Boston, and M. Tascan

ABSTRACT

Nonwoven fabrics are ideal materials for use as acoustical insulation product because the fibers in the structure form void volumes, which entrap air. In fact a typical high loft nonwoven consists of about 10% fiber and 90% air for acrylic needled blanket, 2% fiber and 98% air for polyester auto air filter wrap, and 0.7% fiber and 99.3% air for fiberglass insulation material. The voids serve as reverberation chambers for acoustical insulation. The most important structural property for acousti-cal insulation is thickness of the nonwoven fabric. The thicker the material, the more possibility for the sound wave to touch the fibers in the structure. The other important parameter is the density of the fibers in the nonwoven material. The more fibers per unit volume at the same thickness, the greater the chance that the sound wave will interact with the fibers. Density also affects the geometry and the volume of the voids in the structure.

Acoustical properties of fabric materials are measured one of the two methods: the impedance tube (ASTM C 384-98) and the acoustic chamber method. Impedance tube method uses very small test samples for acoustical insulation measurements. Big reverberation rooms and big test samples are used on the acoustic chamber method. It is also very expensive to establish that kind of rooms. Because of these disadvantages of the test methods, a direct comparative acoustical properties measurement device has been developed and fabricated on the School of Materials Science & Engineering at Clemson University.

This presentation discusses the acoustical insulation measurement apparatus and some preliminary test results for a range of nonwoven fabric structures.





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Document last modified April 16, 2003