The Opal card is the contactless ticketing system used across Sydney trains, buses, ferries and light rail, so its tap sound has become part of daily travel for millions of commuters in New South Wales. Because the noise is short, clear and instantly recognisable, online creators have reused it as shorthand for Sydney, public transport and the daily commute, especially in travel vlogs, city montages and short-form videos. It remains popular because it conveys location and routine in a single second without needing any explanation.