2015 Volume 36 Issue 2 Pages 126-134
To determine noise radiation characteristics from a semi-underground road structure and to confirm the validity of a calculation method for road traffic noise, we previously carried out an in situ experiment using loudspeakers at a semi-underground road with reflective surfaces under construction. Thereafter, we carried out another experiment at the same experimental site, focusing on the effect of the pavement of an absorptive road surface and of setting absorptive louvers on the aperture part. In this report, experimental results on the effect of the pavement of an absorptive road surface are described. On the basis of the experimental results, the accuracy of a practical calculation method for noise around a semi-underground road, the hypothetical point source method, specified in the ASJ RTN-Model 2008, was discussed. Through the discussion, the practical calculation method was partially revised. That is, the effect of the absorption of the road surface was included in a correction term describing the sound power level of a hypothetical sound source that takes into consideration the multiple reflections between the ceiling and the road surface.