The MetroCard was introduced for New York City transit in the 1990s, and its turnstile acceptance beep became a familiar part of the daily subway commute. The higher-pitched version stands out from the usual tone, making it easy to recognise in recordings of stations and entrances. As creators shared transit clips, travel vlogs, and city memes online, the sound spread beyond New York as shorthand for entering the subway. It remains popular because it instantly places a scene in a busy urban station, much like a simple ding sound effect.