Place it directly after the line that needs to fall flat, then follow it with the Dun Dun Dun sound to underline the moment before the next scene moves on.
À propos de ce son
This is a short Spanish clip built around the single word silencio, lasting about fourteen seconds. It gives the listener a dry, awkward feeling, like a room suddenly going quiet after someone has said too much, and the pause lands as both a joke and a gentle warning to stop talking.