Place it just before a reveal in your edit, then follow it with a dramatic sting for suspense and a boom when the door finally opens to complete the scene.
關於此聲音
This clip is a short, persistent knock on a door, lasting less than half a second, with several sharp raps in quick succession. It feels urgent and slightly impatient, like someone waiting outside who expects an answer right away. The brisk, insistent rhythm makes it instantly recognisable as a knock at the door.