Reduction of equivalent continuous A-weighted sound pressure levels by porous elastic road surfaces

A porous elastic road surface (PERS) is superior to drainage asphalt pavement for reducing highway traffic noise. In earlier research and development, for example using a test track, the difference in sound power level (Lw) of cars has been regarded as the noise reduction effect since it was not possible to measure the change in equivalent continuous A-weighted sound pressure level (Leq) for a series of vehicles on such a limited length of surface. As the result of a comparatively major test construction on a highway, have measured the noise reduction effect of PERS as the difference in Leq. First, we measured the motor vehicle Lw and Leq on each section. However, we found that the neighbouring paved sections also influenced Leq. Next, we calculated Leq according to a highway traffic noise model, using the values of Lw measured in the different paved sections. Since the calculated Leq corresponded approximately with the measured Leq, we could verify the validity of the measured Lw. We again calculated Leq, assuming that each pavement is infinitely long. We assumed the improvement of noise reduction effect of PERS was indicated through the calculated Leq. Consequently, we have found that the noise reduction effect of drainage asphalt pavement was 5-6 dB, whereas that of PERS was 7-9 dB.