Acoustic is currently one of the most important fields of study. Recently, many studies have been carried out in this field and new findings have uncovered the potential use of new materials for sound absorption applications. This paper investigated the sound absorption properties for recycled fibrous materials including natural fibers, synthetic fibers and agricultural lignocellulosic fibers. Nonwovens produced from recycled natural fibers blended with synthetic fibers have been tested acoustically. Also, biocomposites from agriculture wastes such as rice straw and sawdust have been investigated. The results indicated that nonwoven samples have high sound absorption coefficients at high frequencies (2000-6300 Hz), low sound absorption coefficients at low frequencies (100-400 Hz) and better sound absorption coefficients at mid (500-1600 Hz) frequencies. The sound absorption coefficients at all frequency ranges improved by increasing the thickness of nonwovens. Also, adding air space behind the sample improved the sound absorption at low and mid frequencies. The tested rice straw and sawdust composite samples achieved low sound absorption at low and mid frequencies. However, they have slightly high sound absorption at high frequencies. A significant improvement in sound absorbing performance at low, mid and high frequencies was achieved by adding perforation of 6% for the tested sample and increasing the thickness of nonwoven samples. Adding air spaces behind the tested composite systems could improve the sound absorption at low and mid frequencies. Generally, the results indicated that recycled fibrous materials hold promise for use as raw material for sound absorbing, being low cost, lightweight and biodegradability.

Coronaviruses (CoV) are a large family of viruses that cause illness ranging from the common cold to more severe diseases such as Middle East Respiratory Syndrome (MERS-CoV) and Severe Acute Respiratory Syndrome (SARS-CoV). We succeeded in preparing disinfectant cellulose-based wipes treated with antimicrobial and antiviral silver nanoparticles to be used for prevention of contamination and transmission of several pathogenic viruses and microbes to human in critical areas such as hospitals and healthcare centers especially coronavirus. In this work, the antimicrobial and antiviral activities of silver nanoparticles (AgNPs) prepared with four different techniques were investigated for the utilization as a disinfectant for cellulose-based wipes. These four methods are namely; 1) trisodium citrate with cotton yarn as a reducing agent, 2) preparing AgNP's using aqueous solution of PVA in the presence of glucose, 3) trisodium citrate with cotton fabric as a reducing agent, and 4) photochemical reaction of polyacrylic acid and silver nitrate solution. Polyester/viscose blended spunlace nonwoven fabrics as cellulose based fabrics were treated with the prepared silver nanoparticles to be used as surfaces disinfection wipes. The properties of the nonwoven fabrics were examined including thickness, tensile strength in dry and wet conditions in both machine direction (MD) and cross-machine direction (CMD), bursting strength, air permeability, water permeability and surface wettability. Characterization of the AgNPs was carried out in terms of UV-VIS spectroscopy, TEM, SEM, and Zeta potential analysis. The assessment of AgNPs active solutions for antimicrobial and antiviral activities was evaluated. The results obtained from the analyses of the AgNPs samples prepared with different techniques showed good uniformity and stability of the particles, as well uniform coating of the AgNPs on the fibers. Additionally, there is a significant effect of the AgNPs preparation method on their disinfectant performance that proved its effectiveness against coronavirus (MERS-CoV), S. aureus and B. subtilis as Gram-positive bacteria, E. coli and P. mirabilis as Gram-negative bacteria, A. niger and C. albicans fungi.

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