Research Articles

There are ongoing efforts to use eco-friendly sound-absorbing materials to reduce noise pollution. Various sustainable sound-absorbing materials, including agricultural by-products, have been examined in previous research. This study focuses on using pistachio husks as a sustainable sound-absorbing material. To assess the performance, the sound absorption coefficient was determined by filling impedance tubes with pistachio husks to heights of 40, 60, 80, and 100 mm. The sound absorption peak was observed at 0.523 at 1,296 Hz at a fill height of 40 mm, and 0.736 at 532 Hz at a fill height of 100 mm. As the amount of pistachio husks in the impedance tube increased, the sound absorption performance at low frequencies improved. The noise reduction coefficients (NRCs) were 0.456 at 80 mm and 0.428 at 100 mm. This corresponds to a KS F 3503 grade of 0.5M, which shows that pistachio husks have sound absorption properties. However, the sound absorption performance of pistachio husks was inferior to that of other natural materials. Therefore, future research is required to improve the porosity of pistachio husks through various physical and chemical treatments.

Natural fibre composites are globally recognized for their sustainability and functionality, yet challenges such as poor interfacial bonding and high moisture absorption limit their performance. This study developed and characterized a polyester-based hybrid composite reinforced with silane-treated hemp fibres and Lansium parasiticum shell powder—an underutilized agricultural byproduct. The effects of reinforcement loading on mechanical, wear, dynamic mechanical, hydrophobic, and flammability behaviours were systematically investigated. The 3 vol% filler (T3) formulation exhibited maximum tensile and flexural strength, while 5 vol% enhanced hardness and wear resistance. Excess filler loading led to agglomeration and property deterioration. Silane treatment significantly improved fibre–matrix adhesion, thermal stability, and water repellence, as evidenced by increased contact angle and dynamic mechanical analysis results. Overall, the study demonstrated that silane-treated hybrid bio composites offer superior mechanical integrity, reduced moisture uptake, and improved thermal resistance. These findings highlight their potential for sustainable applications in automotive components, building panels, prosthetic sockets, and orthotic supports, contributing to lightweight and eco-friendly material development. This sustainable silane-treated hemp and bio-filler composite demonstrates potential as a next-generation material for lightweight biomedical support and rehabilitation applications in disability research.