Traffic noise can be reduced by porous road surfaces. Investigations have demonstrated the potentials of two-layer porous surfacings with a smooth top layer and an absorption characteristics that is frequency turned to the mechanisms that generates tyre/road noise. The acoustic properties of a set of six different surfaces of a porous type, located on the A17 near Roosendaal (NL), were investigated under conditions of normal traffic. Noise measurements were performed with the Statical Pass-By method on existing traffic. Furthermore the acoustic relevant surface texture and the acoustical absorption characteristics were measured and brought into relation with the obtained noise emission levels. The acoustic measurements resulted in very satisfactory reductions of 4 to 6 dB(A) relative toe an adjacent dense surface of the dab 0/16 type. An important aspect is that these reductions were obtained for both cars and heavy trucks. The noise reducing properties could be related to the surface properties, texture and absorpti.
Samenvatting