In general, a high degree of noise is generated due to rail vibration derived from train passage on a rail joint. Therefore, a countermeasure without providing a large-scale installation such as a sound-proof wall is eagerly demanded. Consequently, as a countermeasure which is easy to install, we have developed a new material named “Noise Insulating Material for Rail Joint, abbreviated to (NIRJ)” mainly to be applied to the insulated joint on long rail lines. The NIRJ is molded in inverse-L shape out of inorganic particles, the diameters of which are from 1-mm to 5-mm, bound with small content of epoxy resin. The NIRJ is installed in a standard position so as to keep a distance between rail and inner side of the NIRJ approximately 100 mm in order that rail joints can be inspected without removing the NIRJ even after them installation. As the result of a test intended to verify noise reduction effect of the NIRJ on a conventional commercial line with a ballasted track, approximately a 2-dB decline of noise was confirmed when trailer cars passed on the rail joint installed with the NIRJ.
In “the Environmental Quality Standards for Noise,” spatial evaluation was introduced. In order to do spatial evaluation in the residential area facing roads, it is necessary to grasp the insertion loss caused by the buildings. The authors proposed in the previous study a simple method to predict the insertion loss of road traffic noise caused by detached houses in case of an area facing a dense asphalt paved road. However, there are lots of residential areas facing the drainage asphalt paved road. Since the frequency characteristics of road traffic noise between dense asphalt pavement and drainage asphalt pavement are different, it is expected that the insertion loss by the buildings changes. The purpose of this paper is to derive a new method to predict the insertion loss of road traffic noise caused by detached houses in case of an area facing a drainage asphalt paved road. A one-twentieth scale model experiment is performed. On the basis of the experimental results, to extend the authors’ previous predicting method to be applicable in case of an area facing a drainage asphalt paved road is examined, and then a simple procedure to compensate the change of noise level caused by the difference of the frequency characteristic is derived. The results of an additional experiment and numerical analyses verify the validity of the proposed method.