Put it right after the failed moment in a short edit, then follow it with the sad violin to stretch the joke, or lead into it with the wrong answer sound when a quiz guess misses.
关于此声音
This is a short, under-a-second wah-wah clip built around a descending, voice-like wail that drops in pitch as it goes. It gives a quick sense of comic disappointment, like a small plan quietly falling apart, and it lands best as a light, knowing reaction rather than a big dramatic sting.