Nano-fibrous composite sound absorbers inspired by owl feather surfaces

This study reports the development of a bionic sound absorber inspired by the layered microstructure found on owl feather surface. The so-called bionic sound absorber is made of a thin nano-fibrous membrane backed with a substrate melamine foam layer (NMSMF). The effects of nanofiber diameter, and the thicknesses of nano-fibrous membranes and substrate melamine foam layers on the sound absorption coefficients are systematically analyzed. The study identifies a cut-off frequency at which sound absorption coefficient suddenly increases. The effect is partially explained based on the permeable and impermeable membrane models. This finding may shed new insight into designing novel semi-permeable sound absorbers possessing a cut-off effect for engineering applications.