NS is the Nederlandse Spoorwegen, the main passenger railway operator in the Netherlands, and 'inchecken' is the Dutch word for tapping in with an OV-chipkaart before boarding. The confirmation tone from its gates and poles is one of the most familiar everyday sounds for Dutch commuters. Online, creators lift the short beep for travel vlogs, trainspotting clips and relatable commute memes, where a single tone instantly sets a station scene without any narration. Its appeal is pure recognition: millions of travellers hear some version of it every day.