loudhailer

The police officer used a loudhailer to tell the crowd to move back.

警察用扩音器告诉人群往后退。

用法提示：loudhailer 为名词，指便携式电子扩音器，用于放大声音向人群喊话。

We could hear the coach's instructions through his loudhailer from across the field.

我们能从球场另一端听到教练通过扩音器发出的指令。

用法提示：句中 loudhailer 作介词 through 的宾语，表示教练使用的扩音器。

The lifeguard picked up a loudhailer and warned swimmers about the strong current.

救生员拿起扩音器，警告游泳的人注意强大的水流。

用法提示：loudhailer 作动词 picked up 的宾语，指救生员用来提醒游泳者的扩音器。