I was wakened by a knock at the door.

敲门声把我吵醒了。

They heard a knock at the front door.

他们听到前门有一敲门声。

They were interrupted by a knock at the door.

他们被敲门声打断了。

Late that evening, there was a knock at the door.

那天深夜，有人敲过门。

There was a knock at the door.

门外传来敲门声。