Implementation of measurement uncertainties into vehicle noise regulation

The current vehicle noise regulation UN R51.03, does not provide specific considerations for the measurement uncertainties related to the measuring method for external pass-by noise. The measurement method is based on the ISO Standard ISO 362-1:2007. While the ISO system mandates a detailed description of the expected uncertainties, the UN-ECE has not overtaken these uncertainty considerations, as the application of the test method is limited to type-approval and conformity of production measurements, both under control of the vehicle manufacturer in agreement with a type- approval authority. The UN ECE Working Party on Noise and Tyres (GRBP) in Geneva established in 2019 an Informal Working Group on Measurement Uncertainties (IWG MU), to evaluate the measurement uncertainty in general and to propose amendments to regulations to reduce the measurement uncertainty, starting with the most important sound emission regulations UN R51.03 (vehicles) and UN R117.02 (tyres). This paper describes the principal work of the IWG concerning the contribution of the different parameters to the overall expanded uncertainties when testing vehicles according to the specifications in UN R51.03. The identified main contributors to the overall measurement uncertainties are variations due to the test track (site-to-site) and air temperature effects (day-to-day).