Place it at the end of a boarding scene, just before the cut to the train pulling away, then follow it with a Bell Ding to mark the departure moment.
Über diesen Sound
This 3.7-second clip is the short electronic chime that warns passengers an MTR train door is about to close, with a brisk, repeated tone that cuts through station noise. It feels urgent and familiar, like the last-second rush to board, and it instantly places a listener on a busy Hong Kong platform.