This document specifies a test procedure, environment and instrumentation for measuring the exterior sound pressure levels from road vehicles under stationary conditions, providing a continuous measure of the sound pressure level over a range of engine speeds. This document applies only to road vehicles of categories L, M, and N equipped with internal combustion engines. Vehicles where an internal combustion engine cannot operate when the vehicle is at stationary conditions are outside the scope of this document. The method is designed to meet the requirements of simplicity as far as they are consistent with reproducibility of results under the operating conditions of the vehicle. It is within the scope of this document to measure the stationary A-weighted sound pressure level during — type approval measurements of vehicle; — measurements at the manufacturing stage; — measurements at official testing stations; — measurements at roadside testing. This document specifices a test method to determine a reference sound level which is unique for the vehicle and therefore not suitable to compare against a general limit, as test condition, microphone condition location relative to the sound sources can vary significantly. The test conditions in proximity and at engine speeds significantly higher compared to real operation conditions in traffic are deliberately chosen to enable in-use tests at higher background conditions, which are typical for road-side checks. Technical background information is given in Annex A.