Some players manually swap the hurt files in their Minecraft directory for the legacy .ogg versions, often using tools like Audacity for clean audio extraction.
The sound was one of three grunting vocalizations uploaded to Freesound.org in 2007 by a user named thecheeseman . minecraft_damage_oof_sound_effect_hd
Since the classic sound is still a favorite for many players, several community-made resources allow you to restore it: Some players manually swap the hurt files in
Why did they change the “ooo” damage sound? : r/Minecraft minecraft_damage_oof_sound_effect_hd