New ISO Test Track Specification for Measuring Tire and Vehicle Noise

International standard ISO 10844 is applicable to test tracks used for evaluating vehicle exterior (pass-by) noise. The objective of the standard is to provide a high degree of reproducibility between different test tracks. Toward that objective, the standard specifies properties of the test track to (a) ensure that noise propagation is not significantly affected by the surface, and (b) minimize the variability of tire-pavement noise generation. There are significant changes in the methods of measuring the pavement's acoustic absorption and texture properties compared with the 1994 version of the standard. Acoustic absorption affects noise propagation over the surface, and the standard now requires the two-microphone impedance tube method measured in situ. Pavement texture affects tire-pavement noise generation, and the standard now specifies laser-based profiling methods. Advantages and benefits of the new test methods are described along with practical techniques to help ensure valid measurements. The article also explores the possibility of supplementing ISO 10844 measurements with standard tire-pavement noise testing using the on-board sound intensity (OBSI) method. This additional test provides a direct measure of the tire-pavement noise response, which can be compared to the pavement texture being used as an indirect indicator of this response. The OBSI method also allows for a measure of the variability of tire-pavement noise along the length of the test track (spatial variability).