Beeps: Two of the sounds on a train
12 May 2014 Last updated at 11:40 BST
While some beeps on trains serve a clear purpose - closing doors, for example - not all of them are obvious.
These mysterious beeps have been the subject of internet message board speculation.
But it turns out they are crew-to-crew communications such as from the dining carriage or driver to staff elsewhere on the train.
Here are two examples.