Sound power level of road vehicles running on dense asphalt pavement at various sites in Japan

Road traffic noise is one of the major environmental issues in urban areas. In Japan, the road traffic noise prediction model ‘‘ASJ RTN-Model 2013,’’ which has been developed by the Research Committee in the Acoustical Society of Japan (ASJ), is used widely in environmental impact assessment. Several calculation formulas for the A-weighted sound power level, L_WA, of each type of road vehicle are specified in this model. Among them, the formulas for L_WA of road vehicles on dense asphalt pavement have been derived using the measurement data acquired in 1991–1998. In this study, to improve the accuracy of L_WA for dense asphalt pavement, pass-by noise measurements were performed on 40 actual roads during the last decade. The results revealed that L_WA of passenger cars, including hybrid vehicles and mini-sized vehicles, was 1.1 dB lower than that adopted in ASJ RTN-Model 2013. Regarding the other vehicle types such as large-sized vehicles, the differences between L_WA obtained from field measurements and those in the model were 0.5 dB or less, and no marked changes in L_WA were found.