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

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.