The 'duh' reaction sound does not point to one single widely agreed source in this listing, but the expression has long been used in comedy and internet culture as a sarcastic way to say something was obvious. Short audio versions spread well on soundboards, meme edits and reaction clips because they are instantly recognizable and easy to drop into almost any format. Its staying power comes from that simplicity: one word, clear tone, and a fast payoff that fits fails, sarcastic captions and awkward moments.