alarm barrel

例句：

1. 1. The policeman was alarmed by the sudden noise.
   警察对突然的噪音感到惊慌。
2. 2. The old man was alarmed by the sound of a car approaching.
   老人被汽车的声音吓了一跳。
3. 3. The alarm barrel was filled with water to prevent it from leaking.
   警报筒里装满了水以防止它泄漏。