隨著都市發展，軌道運輸更貼近人們生活圈，因此惱人的噪音更加影響生活。根據文獻中指出，軌道系統的噪音主要來自於鋼軌的振動，因此為減低噪音，如何抑制鋼軌的振動為其重點。
　　本研究共分為三部分，第一部分利用實驗找出鋼軌之主要振動頻率及衰減率，可更加了解鋼軌振動特性及各振動頻率之衰減程度。第二部分為裝設動態吸振器，對鋼軌主要振動頻率之影響比較。動態吸振器為在鋼軌上加裝一自由度之系統，大部分型式為質量塊及橡膠阻尼組成，用途為抑制鋼軌之振動，更進一步降低噪音。第三部分為驗證動態吸振器之減振效果，利用衰減率及加速度均方根值比較。
　　鋼軌水平方向主要頻率為450Hz，垂直方向主要為1000Hz，軌枕影響鋼軌振動頻率為200Hz~270Hz，機車車輛影響鋼軌振動頻率約為3000Hz，其頻率會根據試驗地段不同略有所不同。
　　鋼軌衰減率於該方向主頻略低處會有較低之衰減率，因鋼軌主頻較易被激發，於振動傳遞時會較顯著，因此衰減率較低。低頻相較於高頻處，其衰減率較高，因低頻主要為軌枕所影響，其能量較易被軌枕吸收，故衰減率較高。
　　本研究設計之動態吸振器，並未影響鋼軌主要振動頻率，於水平方向衰減率並未提高；垂直方向衰減率之低頻與高頻處其衰減率有提高，主頻附近差距不大。對於水平方向加速度均方根值約增加1.6dB，垂直向加速度均方根值約降低1.7dB。本研究之動態吸振器對於垂直方向振動有些微降低，但於水平方向並無作用，應為整體質量不夠及橡膠阻尼吸振程度不夠所致。

Rail transport systems have some complaint about noise from the railway. The noise causes the vibration of the rail. To reduce the noise, a efficient way to reduce the rail vibration. To achieve this, dynamic vibration absorbers are sometimes designed.
In this paper, rail’s frequency was found from experiment. Rail’s horizontal frequency is 450Hz, and vertical frequency is 1000Hz. The frequency is 200Hz to 270Hz, because of the sleeper. The frequency is about 3000Hz, because of the train. The same, decay rate on the track was found from experiment.
The dynamic vibration absorber can be used to reduce the vertical decay rate on the low frequency and high frequency, and reducing the vertical acceleration’s root mean square value. On the contrary, the dynamic vibration absorber’s decay rate in horizontal was useless.

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