Abstract
Acoustic properties of drainage asphalt are investigated to simulate the noise propagation of road traffic noise. Normalized acoustic impedance, porosity and flow resistivity are measured by an ordinary method with a small sample of maximum size of aggregate 13 mm and thickness of 45 mm. By referring to Allard's impedance model for rigid frame porous material and curve fitting technique, tortuosity of the sample is deduced. It is shown that this model gives a good fitting to normalized acoustic impedance measured and applicable to simulate the noise propagation on the drainage asphalt of road surface by a boundary element method. Next, effective flow resistivity is deduced approximately by a short range sound propagation over a drainage asphalt surface of a highway in operation. It is shown an empirical one-parameter impedance model is applicable to the prediction of noise propagation on the drainage asphalt surface by using an effective flow resistivity. Normal and random incident absorption coefficients are measured and presented for data supplements.
