free vibration

例句：

1. 1.The mechanical system has a free vibration frequency of 20 Hz.
   这个机械系统的自由振动频率为20赫兹。
2. 2. The scientist noticed that the material had a free vibration mode at 500 Hz.
   科学家注意到该材料在500赫兹处有一个自由振动模式。
3. 3. In the study, we found that the free vibrations of the material were responsible for its unique properties.
   在该研究中，我们发现材料的自由振动对其独特的性质负责。