Two-layer asphalt (double layer drainage asphalt) pavement reduces noise better than not only dense asphalt pavement but also drainage asphalt pavement. This paper first introduces thepresent conditions of two-layer asphalt pavement in Japan and its specifications, and then discussesthe characteristic of noise reduction effects from two aspects. One is the relationship between theimpact on tires when they contact the road surface and the pavement type. The pavement types usedfor comparison include two-layer asphalt pavement, drainage asphalt pavement, dense asphaltpavement and concrete pavement. The other aspect is the relationship between the acousticabsorption coefficient of each pavement type and the spectral distribution of noise reduction effects.Experiment results showed that the impact on tires was less on two-layer asphalt pavement than on drainage asphalt pavement. This suggests that two-layer asphalt pavement reduces noise better than drainage asphalt pavement. The results also showed that the acoustic absorption coefficient of twolayer asphalt pavement laid on a test course was larger than that of drainage asphalt pavement by 0.05 to 0.08 in the frequency band of 800 to 1,250 Hz. This suggests, but does not necessarily demonstrate, that two-layer asphalt pavement reduces noise better than drainage asphalt pavement in the frequency band of 500 to 800 Hz.
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