Carbonized and Activated Non-wovens as High-Performance Acoustic Materials: Part I Noise Absorption

Noise absorption is one method for noise reduction in engineering. The material acoustic property for noise absorption is principally based on the efficiency of material structures for damping sound wave reflections. In this paper, three non-woven composites with activated carbon fiber (rayon precursor) non-woven as a surface layer and cotton, ramie, and polypropylene fiber non-wovens as base layers were produced. Their noise absorption coefficients were measured using the Brüel and Kjær impedance tube instrument and compared to those of three glass-fiber-surfaced non-woven composites. Statistical significance of the differences between the activated carbon fiber composites and glass-fiber-surfaced composites was tested using the method of Duncan's grouping. The study concluded that the activated carbon fiber composites exhibited an exceptional ability to absorb normal incidence sound waves. The analysis also revealed that the activated carbon fiber composite with a cotton base layer would be 4.6 times lighter in weight, 14% higher in low-frequency absorption, and 7% higher in high-frequency absorption, in comparison with the composite having a glass fiber surface layer and a polypropylene fiber base layer.