In the past two decades, the rapid growth of industries and urbanization driven by economic development has led to numerous environmental problems, including noise pollution. Today, noise pollution has become a significant threat to human health. One of the most effective methods for reducing noise pollution is the use of sound absorbers. These absorbers are categorized into two types: viscous and resonant absorbers. Woven textiles, due to their thin structure, generally exhibit minimal viscous sound absorption. However, when an air gap is placed behind them, the sound absorption shifts from viscous to resonant, improving acoustic performance, especially at low and mid frequencies. The aim of this study is to enhance the acoustic performance of woven textiles, particularly through the introduction of double-layer weaves. To achieve this, various fabrics were woven using honeycomb, 2/2 twill, double-layer twill, weft-backed, Mock-leno, and double-layer with filler yarn structures on an experimental weaving loom, utilizing viscose yarns at different densities. The air permeability, thickness, and density of the samples were measured. The sound absorption coefficient (SAC) was eva‎luated using the two-microphone impedance tube method and transfer function, under three conditions: without an air gap, with a 20 mm air gap, and with a 40 mm air gap. The study examined the impact of weave structure, weft density, front and back side of the fabric, and air gap on SAC, noise reduction coefficient (NRC), and sound absorption average (SAA). The results indicated that denser fabrics exhibited higher SAC, NRC, and SAA values compared to less dense fabrics. It was found that with an increasing air gap, the absorption spectrum transitions from viscous to resonant, leading to higher SAC at low and mid frequencies. Additionally, increasing the air gap resulted in the peak SAC shifting to lower frequencies. The highest and lowest NRC and SAA values were observed in the double-layer twill and honeycomb fabrics, respectively. It was also determined that, for most samples, an increase in air permeability led to a decrease in NRC and SAA. The findings showed that the sound absorption spectrum was nearly identical on both sides of the fabric for honeycomb, 2/2 twill, and Mock-leno structures, where the weave design is the same on both sides. However, for other weaves, where the front and back weave designs differ, sound absorption differed between the two sides. The double-layer twill fabric was identified as the best sample in terms of acoustic properties. Finally, this fabric was placed over a polyester nonwoven fabric with thicknesses of 20 mm and 40 mm, and the acoustic properties of this composite structure were investigated. It was found that although placing the woven fabric over the nonwoven fabric increased sound absorption, the acoustic performance of the woven fabric was better when a similar air gap equivalent to the thickness of the nonwoven fabric was placed behind it.

پرهام سلطاني , محسن شنبه

ابراهيم تابان

محمد قانع , مهدي حجازي