Abstract
Reduction in noise pollution in general and particularly in automotive industry has become an important issue that has gained the interest of numerous researchers. The present research is aimed to introduce a new product which could serve as an alternative for other commonly used sound absorbing materials. It is expected that hollow fibers due to their structure can significantly influence noise insulation performance of materials in which these fibers are incorporated. Therefore sound absorbing material compose of blend of natural hollow fibers Milkweed or as it known Estabragh and hollow polyester fibers were used to produce needle-punched nonwoven samples. Eighteen different samples were produced by varying blend ratio, mass per unit area, punching density, and frequency of the incident sound. Noise Absorption Coefficient (NAC) of the samples was evaluated using impedance test method. The evaluation procedures were designed using Taguchi method. Results showed samples solely comprise of Estabragh fibers have attained the ability to absorb noise. It was observed that NAC decreases as the amount of Estabragh in the blend is reduced. Although the results showed an increase in punching density improves NAC of the samples, however statistical analysis dismissed the effectiveness of this parameter on sound absorption characteristics of the samples. It was found that NAC increases in direct relation to increase in mass per unit area (g/m2) of the samples. This was attributed to the increase in tortuosity of the samples and the energy losses due to frictional resistance. Finally it was observed that NAC peaks at frequency of 4000 Hz.
Highlights
Undesirable noise is potentially hazardous and create major health problem in different areas of applications as workshops, residential/ office buildings and transportation
In order to evaluate the acoustic performance of the lightly needled nonwovens samples, the noise absorption coefficient measurement based on ASTM-E 1050-1982 was repeated three times for each sample
The results from Taguchi analysis indicated that the Estabragh fibers presence in nonwoven structures improves the acoustic performance of samples
Summary
Undesirable noise is potentially hazardous and create major health problem in different areas of applications as workshops, residential/ office buildings and transportation. Hassanzadeh [12] have investigated the acoustical performance of Estabragh hollow fibers blended with polypropylene fibers in forms of needle punched nonwovens. They concluded that increasing the Estabragh fibers content in blend significantly leads to increase nonwovens sound absorbency. Mahmoud [4] investigated the effect of hollow fibers component on acoustical performance of nonwoven structures.
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