Aerodynamic noise reduction by pile fabrics

Pile fabrics are known to be effective at reducing aerodynamic noise. However, it is not clear which kind of pile fabric is most effective at reducing noise and what the noise-reducing mechanism is. In this paper, simple experiments using a cylinder with and without pile fabrics clarify that the flow resistance of pile fabrics is an important parameter in reducing aerodynamic noise. Light resistance is preferable and the optimum filling rate of pile fabrics is around 1%. The noise-reducing mechanism of pile fabrics is discussed and clarified by comparing measured flow properties with computational fluid dynamics (CFD) results, which simulate pile fabrics by the porous media model with light flow resistance.