Abstract
It is reported that not only an audible noise but also a low-frequency noise is radiated from a high-speed train toward a way-side area in an open section. The observed the low-frequency noise, which is defined here as the noise of below 80Hz including the infrasound of below 20Hz, consists of hydrodynamic pressure variation around the nose and tail part of the train and low-frequency acoustic pressure wave by aerodynamic sound sources around the train as well as vibrating surfaces of a viaduct structure. We use an acronym PF (Pressure Field) for the former phenomenon, and PW (Pressure Wave) for the latter. In the past, we measured the wayside low-frequency noise in a fully open section, however the causes of the PW still remained to be fully clarified due to lack of sufficient data. Hence, we have measured the PW in the wide range of the train speed of 150〜400km/h. From the obtained characteristics of spectra, distance attenuation and velocity dependency, the major component of the PW in the far field is found to be aerodynamic sound emitted from the train, in a high-speed region of over 350km/h.
