直流馬達推桿是廣泛應用於醫院之電動病床的產品，其功能在於使病床能夠有電動升降之功能，以便使病人能輕鬆地調整病床，而因為所使用的環境是在醫院這種低噪音的環境，所以推桿對於噪音大小的要求也相較嚴格。本研究將對推桿以及其外殼進行分析，以ANSYS有限元素分析軟體以及實驗量測求得推桿外殼的結構與聲場特性，找出振動與噪音產生的原因。之後由分析之結果作為依據對其外殼進行改善，希望能有效降低推桿運轉時所產生的振動與噪音。本研究所建議的新設計，可使直流馬達推桿之噪音下降約5.5dB。

This research focused on the structural and the acoustic characteristics of an electric actuator which is used in the hospital bed. The noise is restricted because the actuator is usually placed in a low-noise environment. Therefore, the noise reduction of the external ABS shell of the actuator was also studied.
A finite element analysis software, ANSYS, was used to obtain the numerical solutions of the vibration characteristics of the shell. Experiments of vibration and noise measurements, the while the actuator was operating, were conducted. The numerical and the experimental results are generally compared well. The ABS shell was then modified to avoid excessive vibration and noise by moving the natural frequencies of the system away from the exciting frequency from the actuator. The best result is the reduction of 5.5dB in noise level.

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