摘要
捷運系統已是許多城市積極發展的大眾運輸系統，它非常便利及快速，但伴隨而來的是列車行駛時產生的噪音。本文探討軌道高架橋振動及結構噪音的特性，以台北捷運U型混凝土高架橋在列車通過時所造成的結構振動產生噪音。 首先分析高架橋結構橋面板及側牆的振動頻率響應，討論列車通過容易激發之自然振動模態，並觀察其模態振型。討論聲壓頻率響應與振動頻率響應的差異性，觀察這些自然頻率的模態振型與聲場分佈的關係。此外，討論結構噪音在高架橋上方、下方、水平方向聲壓位準隨距離衰減的情形，討論高架橋下有與無地面對於聲場有何影響。最後在鋼軌下加入高隔振基鈑，討論振動及結構噪音降低的情形。本研究結果顯示地面反射聲波的影響，聲壓位準在地面上方4公尺以上受地面反射影響不大；以距左側軌道中心水平距離15公尺觀察噪音，使用高隔振基鈑可降低聲壓位準3.3dB(A)。
並列摘要
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.