non-stationary vibra-tion

例句：

1. 1. The car's engineis producing non-stationary vibrations.
   汽车发动机产生的是非稳定振动。
2. 2. The building's foundation is experiencing non-stationary vibrations due to the earthquake.
   由于地震，这座建筑的地基正在经历非稳定振动。
3. 3. The scientist observed that thematerial was exhibiting non-stationaryvibrations during the experiment.
   科学家观察到，在实验过程中，该材料表现出非稳定振动。