Field Measurements of Sound Power Levels of Vehicles Running on Japanese General Roads

Sound power levels of vehicles are essential for prediction and assessment of road traffic noise. The authors have been collecting the data of the sound power levels of Japanese vehicles running on Japanese general roads for several years. In this paper, the collected sound power levels and the sound power spectral characteristics of running vehicles measured during pass-by on 22 measurement sites in Japan are reported. Measured vehicles were categorized in large-sized, medium-sized and small sized vehicles, and the measured sound power levels in A-weighting (LWA) were arranged as a function of running speed according to the ASJ RTN-Model, which is used as a standard prediction method for environmental impact assessment in Japan. From the measurement results, considerable variation of the strength of the vehicle source due to the difference of the measurement sites was found, and the variation is quantitatively discussed in relation with roughness characteristics of road surfaces.