مقاله انگلیسی رایگان در مورد جذب صوتی کارآمد در ساختمان ها – الزویر 2019

In this paper sound absorption characteristics of silica aerogel/polyester (PET) blankets are investigated. PET fibers were made on an industrial scale compact melt spinning line and then processed on a laboratory scale needling line to produce nonwoven fabrics. The silica aerogel blankets were prepared by in situ synthesis of silica aerogel on the nonwoven fabrics via a two-step sol-gel process of tetraethoxysilane which was followed by drying at ambient pressure. In order to achieve aerogel particles with different pore structure and properties, various synthesis conditions were used. The nonwoven samples were characterized in terms of thickness, fiber diameter, porosity and pore size by X-ray micro-computed tomography and scanning electron microscopy. Moreover, nitrogen adsorption analysis was carried out to determine the specific surface area and pore structure of aerogel particles. The effect of pore structure, physical properties and hydrophobicity of aerogel particles on sound absorption coefficient (SAC) of blankets was investigated using two-microphone transfer function method. Also, the effect of sol volume and nonwoven thickness was investigated. The results indicated that at all frequency levels, silica aerogel/PET blankets enjoy higher SAC than their untreated counterparts. It was found that, SAC is strongly affected by the pore structure of aerogel particles. Silica aerogels with lower bulk densities, larger pore size and higher porosities exhibited better sound absorption performance. The results also indicated that hydrophobic aerogel blankets exhibit higher SAC as compared with hydrophilic blankets. The results also showed that the thickness of nonwoven fabric strongly affects the SAC of aerogel blankets.

Introduction

In recent decade, noise pollution has become the most widespread and least controlled environmental issue. Noise pollution causes or contributes to not only psychological disorders, but also cardiovascular disease, loss of hearing, high blood pressure and tinnitus hearing impairment. Thus technological control of acoustical behavior of industrial products is a fact that has to be scientifically faced by researchers [1]. This control can be achieved using either sound insulating or sound absorbing materials. Conventional various sound absorbers such as foam-like materials or nonwoven fabrics as low-density porous materials can prevent reflection of the incident sound waves and hence increase sound absorption. The use of nonwovens, as widely accepted porous sound absorbing materials, has been extensively researched [2–6]. Since more than a decade, acoustic engineers have been looking for lightweight sound absorbing materials in buildings. The challenge primarily stemmed from inability of conventional bulky nonwoven fabrics and foams to absorb sound waves, specifically sound waves of low frequency bands that impair speech comprehension [7,8].