The most distinct sign of an oncoming train is the horn. For diesel and electric trains, this is often a loud, multi-tone air horn used to alert commuters and workers.
Watch a demonstration of how realistic train approach sounds can be layered and triggered in a simulated environment: TRAIN Sound Effects - Train Approach krc Videos YouTube• Jun 10, 2016 Key Elements of a Train Approach TRAIN Sound Effects - Train Approach
As the train nears, you hear the "chugging" of steam engines or the low-frequency "thrum" of diesel prime movers. The most distinct sign of an oncoming train is the horn