We heard the whistle of a train.

我们听到了火车的汽笛声。

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

当中午的笛声响起时，工厂里的嘈杂声顿时停止了。

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

这些汽车听到愈来愈的警笛声便停了下来。

I heard police sirens in the distance .

我听到警笛声从远处传来。

In big cities you always hear sirens all the time.

在大城市里, 你总能听到警笛声。