In this study, the effects of physical parameters on sound absorption properties of nonwoven fabrics were investigated. Eight different nonwoven composites including different fiber types mixed with different ratios were tested. Along with sound absorption properties, thickness, weight per area, and air permeability parameters of the samples were measured. The increase in thickness and the decrease in air permeability results in an increase in sound absorption properties of the material. The samples including 70% cotton and 30% polyester resulted in the best sound absorption coefficient in the mid-to-high frequency ranges. The increase in the amount of fiber per unit area resulted in an increase in sound absorption of the material. Addition of acrylic and polypropylene into a cotton and polyester fiber mixture increased the sound absorption properties of the composite in the low and mid-frequency ranges also.

Growing interest in sound absorbing materials in industrial applications is their maximized low frequency properties. This research focused on improvement of sound absorption characteristics of layered nonwoven composites. Two different nonwoven structures as polyester and polyester/polyamide blend, were selected as top layer of the bilayered structure. Combinations of a control top layer and a variety of base layers were tested for their sound absorption properties and the effect of using; 1) polyester or 2) polyester/polyamide top layer was investigated. Development of composites with microfibrous layer of 70 %Polyester/30 %Polyamide fibers backed with either of 70 %wool/30 %bi-component polyester, 70 %Cotton/30 %Polyester or 70 % equivalent blend of acrylic, cotton, polyester and 30 % polypropylene nonwoven fibers, provided exceptional sound absorption properties at low frequencies. Macrofibrous layer of polyester fibers backed with 70 %wool/30 %bi-component polyester fibers improved sound absorption properties at all frequency ranges.

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