A method to evaluate the aeroacoustic bogie noise of Shinkansen high-speed trains by considering the acoustic field

Abstract

The reduction of the aeroacoustic bogie noise that is generated by the Shinkansen high-speed trains travelling faster than 300 km/h is an important environmental issue. Currently, the amount of aeroacoustic bogie noise can be quantitatively estimated at the measuring points based on a spatial distribution of the sound pressure level (SPL) that is obtained by a two-dimensional microphone array in a wind tunnel test. However, it is necessary to appropriately consider noise generation and sound field with respect to various acoustic properties such as ground reflection and insertion loss of a bogie side cover. In this study, the transfer function between the integrated spatial distribution of SPL and the results that are obtained by an omnidirectional microphone are calculated by a numerical method. The aforementioned transfer function is calculated based on the bogie conditions that the side cover would be set and that the ground reflection effect would also be included. The transfer function is observed to change significantly in the lateral direction in low-frequency regions, especially in the 125 and 160 Hz bands. These spatial trends are also confirmed using an acoustic test that is based on the reciprocal theorem, and it is observed that these trends are caused by the interference between the reflection waves from the ground, the cavity upper wall, and the side covers. The SPL of the aeroacoustic bogie noise of Shinkansen trains can be estimated using this transfer function and can be compared with the results that are obtained from the field tests.