Study of analysis method of interior noise in railway cars by means of ray tracing method

Abstract

We have studied the analysis method of interior noise in railway cars by means of a ray tracing method. Firstly, by using a point source as input, sound distribution inside a car was analysed and compared with the measurement result obtained by a loud speaker test. It was found that the analysis result of sound decay along the longitudinal direction of the car did not always match the measurement result. It is possibly because the wave character of the sound cannot be strictly simulated by the ray tracing method. However, for the purpose of analysing the sound distribution while the train is running, it may not be necessary to accurately simulate the sound decay in the longitudinal direction, because the sound sources are distributed everywhere inside the running car and therefore the importance of the sound decay along the longitudinal direction may be low. Based on this perspective, we have proposed the interior noise analysis method for the running condition by applying multiple sources inside the car. The amplitude of each source was estimated from the measured vibration of the interior panels as well as from the estimated radiation efficiency of each panel. Validation of the analysis was conducted by comparison with the measured data of the interior noise inside the running train, and it was confirmed that the level of interior noise reduction by the installation of passenger seats matched well between the analysis and the measurement.

Keywords

• ray tracing method
• statistical energy analysis
• interior noise
• railway car
• sound distribution