Methodology for determining new CNOSSOS-EU vehicle sound power coefficients using type approval data

CNOSSOS-EU is a standardized framework for strategic noise mapping across the European Union which member states are required to conduct every five years. The framework provides an approach to assess noise from different sources, including road traffic noise. Road traffic noise is primarily caused by vehicles. In CNOSSOS-EU, the vehicle exterior noise is modeled using fixed sound power coefficients. These coefficients were derived from measurements conducted up to 2006. Although significant progress has been made in reducing vehicle exterior noise, the existing model does not account for this technical progress. This paper first reviews the evolution of exterior noise legislation and its impact on vehicle noise levels. It then presents a new procedure for integrating the technical progress into vehicle source modeling in CNOSSOS-EU by incorporating type approval data. For demonstration purposes, this procedure is applied to up-to-date type approval data of M1 vehicles, resulting in a more accurate representation of current noise emissions. This research contributes to the refinement of the CNOSSOS-EU model, aligning it with the current state of technology and providing a more precise basis for environmental noise assessment.