Put it right after a hopeful plan is spoken aloud and the picture cuts to the disappointing result, then follow the beat with a quiet room tone underneath the next scene. For a bigger deflation, precede it with a cheerful success sting so the contrast sets up the drop.
关于此声音
A short musical clip built around a male voice singing the line hello darkness my old friend over gentle acoustic backing, lasting just under four seconds. It feels weary, lonely and darkly funny at once, turning a small failure or quiet moment into an instantly recognisable mood of resigned gloom that listeners use for dramatic effect.