This sound is commonly recognized as a sad Om Nom reaction, referring to the green creature from the Cut the Rope franchise by ZeptoLab. Om Nom clips became popular in mobile game culture and later spread into short meme edits, reposts and reaction videos. The sad version stays useful because it delivers disappointment in under a second without feeling harsh or overly dramatic. Online, it is often used in the same quick-reaction role as a buzzer, but with a cuter and more sympathetic mood.