Parameters affecting sound absorption in fiber composites: a case study for Luffa Cylindrica
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The negative effects of noise pollution on human health have become a problem that the world takes into consideration. Many studies have been conducted to control the noise that causes various psychological and physiological disorders. In this context, producing acoustic materials has increased to control noise pollution that seriously threatens human health such as hearing impairment, rest and sleep disturbance, psychophysiological and mental health problems. In Turkey, the regulation named ‘Binaların Gürültüye Karşı Korunması Hakkında Yönetmelik’ was published in 2017. The purpose of this regulation is to create suitable conditions for all kinds of structures in such a way that the noise level to which people will be exposed does not affect their physical and mental health. Seddeq (2009) stated that different materials and various techniques are used to control noise and create an acoustically desirable environment, and one of these techniques is sound absorption. Depending on the physical properties of the material on the surface from which the sound wave comes, there are different amounts of changes in the sound energy. For this reason, the finishing materials used on the surfaces control the sound. The materials used to absorb the sound can generally be listed as fibers, foams, perforated panels, membranes, resonators, and different composite materials. Nor et al. (2004) and Zulkifli et al. (2008) stated that the preferred sound absorber materials in the construction sector are glass or mineral wool materials. Also, Nor et al. (2004) added that the production of alternative materials remains relatively weak due to glass and mineral wool material’s dominance in the commercial market. However, during the application glass and mineral wool materials used in walls or panels, cause lung and eye problem. The result of the health risks, different materials especially the natural ones, are preferred. Biswal (2016) stated that researchers tend to use organic fibers instead of synthetic fibers in fiber composites, because they have better mechanical properties, are easier to obtain and cheaper. Advantages of using organic fibers as acoustic material; lower costs, easily available, renewable and wear-resistant, ease of application and not threaten human health during application and use. After determining the negative effects of noise on human health and health problems caused by some sound absorbing materials, especially during application, the starting point of this study was ‘Is it possible to produce a sound absorber finishing material using easily accessible materials that do not threaten human health?’. The aim of the study is to provide sound absorption by using environmental friendly composite finishing material to be produced by using natural fibers and to provide the use of this material in places requiring absorption performance. For this purpose, literature searches have been done on the studies with composite materials formed with natural fibers. In these studies, the parameters affecting sound absorption were determined. The literature review was helpful in determining the plant fiber and matris to be used in the study and in deciding the methods in the process. Within the scope of the study, a natural material named ‘Luffa Cylindrica’ fibers were combined with epoxy which is a binder thermoset material, to produce a composite material. Then, composite material samples obtained according to determined parameters were examined and results related to sound absorption performance were evaluated. In the study, the sound absorption performance of the materials was measured using an impedance tube and the thickness of the material and the usage of the fiber forms on the sound absorption were investigated separately. In addition, NRC values of the samples obtained were determined since the Sound Reduction Coefficient (NRC) is important, especially in places requiring improvement or resonance control at high frequencies. The results and comparisons are presented in graphs and tables.