Tyre/road noise measurements on ISO tracks using the modified CPX method

Tyre rolling noise test method specified in the UNECE Regulation 117 is directly used in the Tyre Labelling Directive. Noise level specified on EU Tyre Label of each new tyre available on the European market was determined based on vehicle coast-by noise measurements performed on the standard reference road surface proscribed in the ISO 10844:2014. Available data from investigations by the vehicle and tyre industry and results from the STEER project show that the effect of ISO test track is significant. To estimate the noise variation on existing ISO test tracks, a small Round Robin Test was conducted on 3 of them, as a part of the joint Polish-Norwegian project ELANORE. The modified CPX method was used for this purpose. Measurements were performed for 9 selected tyres of summer, winter and all-season type, with label noise values ranging from 66 to 74 dB. Additionally, 2 standard reference tyres, P1 (SRTT) and H1 (Avon AV4), specified in the ISO 11819-3:2017 were tested. The obtained differences in noise levels for the tested tyres were up to 3.7 dB depending on test track. The ranking of tyres regarding measured noise levels didn't correspond at all to the noise values given on tyre labels.