Inhomogeneity of low-noise wearing courses evaluated by tire/road noise measurements using the close-proximity method

Abstract

Abstract Performing numerous analyses of tire/road noise measurements on low-noise pavements during the last several years, the authors observed significant inhomogeneity of the wearing course in numerous cases, while similar problems were almost non-existent when dense pavements were measured. Three main causes of low-noise pavement inhomogeneity can be defined. The first one is imperfections in the technology used for asphalt mix production and/or errors made during the laying process of the wearing course. The second one is clogging that takes place during the pavement’s service life. The third reason is related to uneven and/or excessive wear of the pavement (raveling and stripping of the aggregate may appear in this case). Findings of analyses of noise data acquired from low-noise pavements (based on 10 m long segments), using the close-proximity (CPX) method, are presented and discussed herein. Significant differences in measured averaged noise levels, up to 1.7 dB, between test sections of open-graded wearing courses that were the same in principle, located on the same road but in different lanes were found when performing CPX measurements. At the same time the test sections of a dense pavement differed by max. 0.5 dB only. The calculated A-weighted sound pressure level variability index Scpx, considered to be an indication of pavement homogeneity, reached the value of 1.69 dB over a 500 m long test section of the porous pavement while the Scpx values for dense pavements were much below 0.5 dB.