The horn comes from live basketball arenas, where an electronic buzzer at the scorer's table signals timeouts, substitutions and the end of periods. NBA broadcasts made that short, piercing blast familiar to millions of viewers who may never attend a game in person. Clips of the sound spread through sports edits and meme pages, often paired with crowd cheering underneath, and it became shorthand online for stopping the action. Creators still use it because the meaning is instant, even for viewers who do not follow basketball closely.