抄録
Perforated plates are usually used to cover fibered grass in the absorptive silencer. The air-flow on the surface of these perforated plates generate an air-rubbing noise in ventilation systems. Estimating the characteristics of this aerodynamic noise is the important technique to product high performance absorptive silencers. Obtaining the database of noise characteristics with respect to the air-rubbing noise, the experiment to measure and to analyze this aerodynamic noise from the surface flow on the perforated plate set in the test duct had been executed with connecting the test duct to the acoustic low noise wind tunnel. Noise powers are proportional to the sixth power of the flow velocity, to the width of the perforated plates, and to the square root of the length. Spectra of this air-rubbing noise have the maximum level on the region of Strouhal number between 0.6 and 1.0. Finally, the most commonsense results were made clear that the perforated plate with thinner, smaller hole and lower ratio of the opening area induce the quieter air-rubbing noise.
