The evaluation of railway noise is very important for planning and designing of new line and investigation of sound isolation work in urban area. There have been presented a number of evaluation methods for noise simulation. Based on the frame of reference used, those methods can be classified into two categories: 1) Methods based on the geometrical acoustic theory and 2) Methods based on the acoustic wave theory. Both methods have advantages and disadvantages. For the methods based on the geometrical acoustic theory, the CPU time is very short but the numerical accuracy is low comparing with the methods based on the acoustic wave theory. On the other hand, the methods based on the acoustic wave theory gives accurate solutions but the simulation becomes a large scale simulation. In the conventional studies, the computed noise level is described by the visualization using computer graphics such as iso-surface. Although the visualization is a powerful tool to understand the distribution of noise, it is difficult to recognize the noise level intuitively.
The present authors have developed experience-based interactive road traffic noise evaluation systems based on the geometrical acoustic theory using VR technology. The system exposes to the users the computed noise level with both the auditory information using sound source signal and the visual information using CG image.
This paper presents a railway noise evaluation system using VR technology. The present system is designed for the use of CAVE and HMD. For the geometric acoustic theory, the ASJ RTN-Model 2013 is employed. In case of railway noise, the noise can be classified into two categories; 1) noise from moving train such as rolling noise, aerodynamic noise, motor and so on, 2) noise from joint of rail (impact noise by the passing of wheel). In order to obtain the noise source data, the observation of noise for various type of train is performed and the steady state noise source data is generated from the observed data. The effect of directivity of sound is important for the railway noise. In this system, the directivity model proposed by Japan railway research institute is employed. The present system is applied to several examples in order to investigate the validity of the system. The present system is useful for planning and designing of new line and investigation of sound isolation work in urban area, also for consensus building for the local residents.
