Effect of air gap on sound absorption in layered composite structures produced of sustainable materials

Numerous materials have been produced to isolate the noise that negatively impacts people's health and productivity at work. Some of these materials are not preferred for usage because they are expensive, inefficient, or harmful to the environment. In this study, composite materials were produced with waste chicken feathers (CF) and polyvinyl acetate (PVAC) binder in different mixture ratios. After CF was washed and cleaned, it was shredded into 2–3 mm lengths with a chopper. Then CF was mixed with PVAC binder and thermal bonding was applied. As a result of the process, composites with a thickness of 10 mm and dimensions of 15 cm × 15 cm were formed. These composite plates are supported by sandwich constructions made of various varieties of polyester-based felt (NW), knitted fabric (KF), leather (L), spacer fabric (SF), and air gap (AG5, AG10, AG15) in thicknesses of 5, 10, and 15 mm. Impedance tubes with four microphones were used to evaluate the sound absorption coefficient and sound transmission loss values of these manufactured structures, and the resulting data were analyzed. According to this; The NW + CFC1 two-layer structure is 0.33 (500 Hz), but when a 15 mm thick air gap layer is added, it is seen that it increases to 0.85 (500 Hz). Other sandwich structures produced also show similar results. The best results were achieved with layered composite structures. Adding an air gap layer between the composite layers to increase sound absorption has improved results, especially at low frequencies. The air gap layer can significantly reduce production costs because it can be used instead of a material layer. The production of textile-based sound insulation structures from the waste material CF is also of great importance in terms of sustainability.