The survey of the high-frequency sounds above 10 kHz radiated from the Japanese high speed and conventional railways

We have reported the results of recent survey of high-frequency sounds above 10 kHz radiated from the Japanese high speed (Shinkansen) and conventional railways, and the difference between impressions on the train noise with and without such high-frequency sounds, as interim report. From both the time-history and the frequency characteristics of wayside noise, the fact was re-acknowledged that the high-frequency sounds were radiated when a train traveled round a curved track and that they could be observed before the train passed by. The sound had dominant frequency components above 10 kHz and differed significantly in the frequency characteristics from common railway noises. And it was also noted that there was a large difference in the sound pressure levels measured by different sound level meters, mainly due to the frequency characteristics above 10 kHz of the microphones. Subjective impression was examined using the train noise with and without the high-frequency components. Seventeen participants aged between 17 and 58 judged the impression of the sounds using semantic differential. The results showed that high-frequency components had a great influence not only on the difference in sound pressure levels measured by different sound level meters as described above but also on the impression of participants younger than 20 years old. The high-frequency sounds above 10 kHz seem to increase the feelings of discomfort and annoyance for the young people who can hear such sounds.