undamped natural frequency of a mechanical system

例句：

1. 1.The undisturbed environment made it easier for the scientist to conduct his experiments.
   未受扰动的环境使科学家更容易进行他的实验。
2. 2.The undisturbed peace of nature is a rare and precious gift.
   未受扰动的自然宁静是一种稀有而宝贵的礼物。
3. 3. The undisturbed silence was broken by the sound of a car engine.
   未受扰动的寂静被汽车引擎声打破。