Abstract
The interior noise characteristics of railway vehicles differ on the basis of the interior cabin position. The level of interior noise above the bogie (end of the cabin) is higher than at the center of the cabin. The authors know that structure-borne sound from the bogie contributes greatly to the interior noise immediately above the bogie. In this paper, we use the measured data obtained at the rolling stock test plant at the Railway Technical Research Institute (RTRI) and apply operational path analysis (OPA) to describe the contribution ratios to the vibration transfer paths from the bogie to the cabin floor. We also investigate the linearity during input/output and identify correlations between the input data to determine the validity of the analysis results. We consider that structure-borne sound from bogies propagates mainly through the parts connecting the bogie and car body such as single-link-type traction devices (traction links), yaw dampers, and air springs. We confirmed that differences in the contributions of these connecting parts depend on their locations with respect to the cabin floor and that the source of the highest contribution differs at different frequency bands. Moreover, the contribution of nearby parts may yield results that are not always significant. When the correlation is high between the parts connecting the bogie and car body, the precision of the derived transfer functions falls. Although a bogie vibrates rigidly in the low frequency region and very high correlations exist between the vibrations of the parts connecting the bogie and car body, the correlation becomes low in the high frequency region. Therefore, we expect that the contribution of each transfer path can be well estimated by applying OPA in the high frequency region for structure-borne sounds from the bogie in particular.
