Place it right after the disappointing reveal in an edit, then follow it with an awkward moment sting to hold the reaction a little longer. For a bigger letdown, pair it with a SpongeBob disappointed clip first, so the sigh becomes the final word on the scene.
关于此声音
This clip is a single female sigh lasting about 1.4 seconds, a breathy exhale with no words, music or other sounds in it. It feels resigned and unimpressed, like a wordless reaction to something disappointing, annoying or too much effort to answer. It gives the listener that familiar sense of giving up for a moment without saying anything at all.