What you're hearing
A carriage at steady speed: a soft, rolling rumble and no announcements. It sits behind you, the way the hum of the carriage does from your seat, while rain runs down the window to your left.
Swap the rain for a Night drive, a Ship's cabin or an Airplane from Travel, or add a Railway station or a Passing train. The Night train starting point is this mix; Last train puts you on the platform instead. These were made with AI and are marked AI in the list.