Simplified method to create vehicle sound model for road traffic noise simulation-By using sound limit value of noise regulation

Road traffic noise prediction model is used to evaluate and analyze current situation and predict future prospect for road traffic noise. The current models such as CNOSSOS-EU and ASJ-RTN (Acoustical Society of Japan-Road traffic noise prediction model) define the fixed vehicle sound power level formulas. There are vehicle sound formulas for limited vehicle categories, but they are not enough to analyze influence of emitted sound from the vehicles in detail. Looking at an actual road, there are several vehicle categories and old vehicles which mean different regulation stages (e.g. sound limit). Since it is not easy to update the vehicle sound formulas with current methodology such as ISO11819-1 (Measurement of the influence of road surfaces on traffic noise -Part1 Statistical Pass-by method), we have proposed the method for creating vehicle sound formulas with less measurements in proving ground. Furthermore, when test vehicles are difficult to obtain as in the case of vehicles that comply with older regulations, we would like to propose an approximated method for practical use from sound limit in vehicle regulation and database in this paper. And the proposed method is validated comparing with the precise model.