Minecarts, when loading into a world, and are stationary or moving do not display the "Minecart Rolls" title in subtitles. This is also the case when in a minecart, one is moving nearby, or pushing a minecart, this does not display in subtitles. In past versions, any below 1.21 when a minecart is loaded in when joining a singleplayer/multiplayer world it displays "Minecart Rolls" in the subtitles.
Maybe define the start of a constant noise, especially if someone else joins in and also hears the noise when it's within hearing range. Disc's also should probably be a "Disc Plays" as they also have a consistent noise when being played in a jukebox.