Nonwoven acoustic panels from Himalayan nettle (Girardinia diversifolia L.) fibre

Abstract

Sound absorption panels are being used extensively to mitigate the problem of noise pollution in buildings. Conventional materials used for sound absorption include glass wool, rock wool, mineral wool, asbestos, melamine, and polyurethane foam. However, recent studies show these materials can cause respiratory and skin problems. This has led to the search for natural and ecofriendly alternatives for sound absorbing materials. Lignocellulosic materials are cheap, renewable, biodegradable, and abundantly available and thus provide a viable option for use as sound absorbing materials. In this study, fibres extracted from the bark of Himalayan Nettle (Girardinia diversifolia L.) were used to prepare nonwoven webs using needle punching technique. Punch density was varied to create webs with variable properties. The effect of punch density on acoustic properties was studied. A positive correlation was observed between sample thickness and the Noise Reduction Coefficient. Samples having punch density of 75needles/cm2 showed the highest Noise Reduction Coefficient, attributable to their greater porosity and lower compactness. The study demonstrates that the morphological traits of the Himalayan nettle fibre, that is, a rough surface, flat elliptical cross-section, and a hollow core, make it an excellent sound absorption material. The acoustic properties can be tuned by varying the properties of the nonwoven web.