A door knock is one of the most widely used everyday sound effects online, appearing in video edits, livestreams, podcasts and short-form videos whenever a new person, delivery or interruption needs to be signalled without showing it on screen. Because the sound is instantly recognisable across languages and cultures, creators in many countries reuse the same short knock for comedy, suspense and jump-scare setups. Its brevity makes it easy to drop into a timeline, loop for a longer knock, or layer with footsteps and a creak, which is why it remains a staple of soundboards and editing libraries.