1·There was a sharp knock on the door.
敲门声大作。
—— 《牛津词典》
2·No sooner had I sat down than there was a loud knock on the door.
我刚坐下就有人大声敲门。
—— 《牛津词典》
3·At that point there was a light knock on the door.
就在这时，有人轻轻地敲门。
4·I was making dinner and heard a knock on the door.
我正在做晚饭时听到有人敲门。
5·If these officials saw the light of oil lamps in someone's home and heard the sound of reading, they would knock on the door and say, "The mayor adds oil for your lamp!"
如果这些官员看到有人家里的油灯亮着，而且听到读书的声音，他们就会敲门说：“市长给你的灯加了油！”
6·While he was half asleep, he seemed to hear a knock on the door.
蒙胧中他仿佛听到有人敲门。
—— 《新英汉大辞典》
7·There was a knock on the door.
有敲门声。
8·A knock on the door.
门上响起一阵敲门声。
9·I knock on the door.
我敲了敲门。
10·Just then there was a knock on the door.
就在这时响起了敲门声。