This International Standard specifies an engineering method for measuring the noise emitted by road vehicles of categories M and N under typical urban traffic conditions excluding vehicles of category L1 and L2 covered by ISO 9645 and vehicles of category L3, L4 and L5 covered by ISO 362 part 2. The specifications are intended to reproduce the noise levels, which are generated, by the principal noise sources during normal driving in urban traffic. (See Annexe A). 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. The test method requires an acoustical environment, only obtained in an extensive open space. Such conditions are usually provided for: - type approval measurements of vehicle - measurements at the manufacturing stage - measurements at official testing stations NOTE 1: The results obtained by this method give an objective measure of the noise emitted under the specified conditions of test. It is necessary to consider the fact that the subjective appraisal of the noise annoyance of different classes of motor vehicles is not simply related to the indications of a sound measurement system. As annoyance is strongly related to personal human perception, physiological human condition, culture, environmental condition there is a large variation and therefore not useful as a parameter to describe a specific vehicle condition. NOTE 2: Spot-checking of vehicles chosen at random are rarely made in an ideal acoustical environment. If measurements are carried out on the road in an acoustical environment, which does not fulfil the requirements stated in this International Standard, the results obtained may deviate appreciably from the results obtained using the specified conditions.