高速鉄道の車両床下における車両下部音の特性評価

抄録

One of the dominant sound sources of wayside noise on a high-speed railway line is the noise from the lower parts of cars which consists of rolling noise and aerodynamic noise. In this study, the lower part noise was measured continuously along a railway line with two microphones installed at close points to each bogie under the car floor, and characteristics of the noise were evaluated by considering the effect of the location of microphones, the type of tracks such as ballasted or non-ballasted tracks, and train speed. As a result, there is large dispersion of the sound pressure level in the frequency range of 2k-3.15kHz band. The fact suggests that rolling noise varies according to the variation of roughness of a rail surface in the wavelength components associated with the above frequencies. Additionally, the sound pressure level on ballasted tracks is lower than that on non-ballasted tracks, because of the sound absorption effect of ballast beds. Therefore, it was found that the data of the lower part noise measured with under-floor microphones included the effect of track conditions such as rail surfaces, track types, and so on. It is expected that the data of lower part noise which is measured continuously on trains is used to predict the wayside noise along railway lines effectively.