Procedures for measurement of noise emitted by various automotive vehicles have been developed and refined by various technical committees of the SAE. These procedures are used for evaluation of vehicles during development and also as the basis for noise regulations. Recent work on the parameters of these procedures indicates that the site used, the vehicle operator, and the ambient weather conditions are all significant factors in the accuracy of test results. Variation between samples of like vehicles also is a significant factor in the attempt to determine noise level characteristics of a given model. Revision of these procedures to minimize the variation in results attributable to variation in test parameters, and to become more representative of typical operating modes of the vehicle, is essential.