A Round Robin Test of CPX devices for the characterization of road surface noise properties
Résumé
Low noise pavements are often used by cities and road authorities as a noise mitigation solution and there is a need to accurately and efficiently characterize their acoustic properties in order to assess, compare and monitor their performances. It could be interesting to develop an acoustic labeling system for road surfaces, similar to the one existing for tyres. Recent works in Europe have developed procedures for that purpose, most of them based on Close Proximity measurements (CPX). The standardized method for CPX measurement was not fixed until very recently and various CPX measuring systems have been developed over the past decade. In France, several measuring systems directly mounted on test vehicles were developed and extensively used especially in urban areas where the low bulk of vehicles was preferred to cumbersome trailer systems. However, the coexistence of these different systems, often equipped with different test tyres, may be problematic for an objective comparison of pavement noise properties. A round robin test was organized in France, the first ever involving six different self-propelled test vehicles and a test trailer. The devices were equipped with different test tyres among which the SRTT tyre defined in the ISO 11819-3 standard. Measurements were performed on different road surfaces on a test track. The objective was to check if all devices could rank similarly the pavements with regard to rolling noise. Three of the test tyres were mounted on two different systems which allowed to identify a possible effect of the carrying device. The results are presented in the paper. They show that the pavement ranking strongly depends on the test tyre. The test tyre is therefore a crucial feature in the pavement noise ranking when absolute noise levels are considered but also when relative performances are compared.