Sound Absorbing Properties of Selected Green Material—A Review

Noise pollution is often overlooked and invisible, but it significantly impacts the quality of human life. One most straightforward solutions to mitigate noise by using sound-absorbing materials. Recently, research trends develop sound absorbing green materials, typically derived from agricultural by-products, have witnessed an uptick. This paper summarizes properties various materials found in literature, including coconut fiber, kenaf rice bran, husk, straw, Hanji (a traditional Korean paper), tea-leaf mandarin peel, pineapple-leaf corn peanut shell, sugar palm trunk, yucca gloriosa fruit stones, wood barks, flax nettle fiber. Natural fibers can be made compressing raw material or manufacturing them into fibrous composites. The key variables that determine absorption performance are thickness density material, as well presence air back cavity. Generally, thicker exhibit better low- mid-frequency range. Moreover, higher associated with at same thickness. Additionally, increasing distance between cavity enhances low frequencies. Thus, these physical variables, rather than specific used, primarily influence capabilities. Therefore, such fibers, granules, porous effective absorbers if their thickness, density, properly controlled.