Place it as the final reaction shot after the failed joke or boast has fully played out, with no other effect underneath it. Follow it with the sad violin for a deflated ending, or precede it with Nelson's Ha-Ha! when you want mocking laughter first and this as the closing line.
Sobre este sonido
A short voice clip, about four seconds long, of someone saying the Portuguese phrase 'Que engraçado' in a flat, cynical delivery. It does not sound amused at all, which is the point. The feeling is dry and unimpressed, like a polite laugh withheld on purpose, turning a weak joke or an awkward boast into a quiet, cutting reaction.