| Summary: | 碩士 === 國立臺灣大學 === 工程科學及海洋工程學研究所 === 101 === The metro system has long been a public transportation system for city development. This convenient and fast transportation system creates the noise problem while the trains are moving. This paper investigates and explores the features of viaduct vibrations and structure-borne noise using a Taipei Metro System U-shaped viaduct model.
Firstly, the frequency response of deck and the side walls of viaduct was analyzed. the modes natural vibration may be predicted by the trains pass by. Secondly, the differences between sound pressure frequency response and vibration frequency response were compared and analyzed and the relationship between the modal shape and sound field distributions were observed. In addition, the decrease of structure-borne noise with the increase of distance was examined in upward, downward, sideward directions. The effects of ground reflection on the noise level was also discussed. Finally the effects of NBHI on the noise attenuation was also investigated. Results of this study showed that, the effects of ground reflection on the noise level in 4 meters above the ground can be neglected for acoustics field. To observe the noise of 15 meters horizontal distance from the center of the track, NBHI can reduce the sound pressure level about 3.3dB.
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