笛声

We heard the whistle of a train.

我们听了火车的汽。

I heard police sirens in the distance .

我听从远处传来。

In big cities you always hear sirens all the time.

在大城市里, 你总能听。

The cars had stopped at the sound of the approaching siren.

这些汽车听来近的便停了下来。

The din in the factory ends abruptly when the noon whistle sounds.

当中午的响起时，工厂里的顿时停止了。