This sound comes from the zombie enemies in Half-Life 2, Valve's 2004 first-person shooter. The game's zombies became memorable partly because of their disturbing vocal effects, which players still recognize years later. Clips of Half-Life 2 zombie noises spread through gaming videos, machinima, and meme edits, especially in horror themed content and Source engine nostalgia posts. It remains popular because it is instantly readable as undead, yet specific enough to trigger recognition from longtime PC game fans.