Determination of in-situ sound insulation for interior noise prediction in railway vehicles

The interior noise of the passenger cabin is determined by the sound insulation of the vehicle structure. In this study, we propose a practical in-situ sound insulation test method in the complete vehicle in the factory before the dynamic type test. First, the omnidirectional speaker was arranged under the vehicle underframe. Then the noise levels and the reverberation times were measured at the underframe, the side of the vehicle, and in the passenger cabin to derive the sound field distribution inside and outside the vehicle. In the same way as the field test, the sound field is simulated through the interior noise prediction model using the hybrid ray-tracing method. In this process, the sound insulation values for each car body components of the railway vehicle are used as input variables. The input sound insulation values are determined with trial and error methods, which show the characteristics most similar to the factory test results. The accuracy of the predicted values was evaluated by comparing the predicted interior noise results and the measured noise in the dynamic test. The predicted interior noise shows good agreement with the measured values.