The STM announced this morning that it is testing a warning sound for metro doors closing that it plans to have installed on all MR-73 trains by 2012. Right now, trains in Montreal's metro don't give any visual or audio indication that their doors are about to close, which sometimes causes people to get caught in them. Other metro systems around the world have such a chime and/or blinking light to indicate that doors are about to close or are closing.
This isn't the first time the STM has come up with this idea. In 2008, it tested a train that had a high-pitched beeping sound. I imagine it wasn't received very well, considering how annoying that beep can be when heard over and over again.
The sound they've come up with this time - you can listen to it in .WAV format (WAV? Really STM?) on the STM's website - is a vocal warning with the famous doo-doo-doo sound of departing trains in the background.
This is significant because the doo-doo-doo sound associated with Montreal's metro system is endangered.
The sound is heard on the MR-73 trains used on the blue and orange lines (a similar sound is heard on three MR-63 trains with middle elements from a specially-designed train). It's not an artificial or intentional creation, but rather a byproduct of a current chopper that regulates power going to the electric motor. This chopper has five stages, which give off sound at different frequencies (three of which are audible by most people).
In new trains that will be built hopefully sometime before the next millennium, the motors will have a much more advanced power regulation system that will result in a continuous frequency change rather than discrete notes. It will sound more like a car engine accelerating than the metro we know now (assuming it makes much sound at all - new trains are supposed to be much quieter).
There has been suggestions among transit fans of artificially emulating the sound by just playing a sound file when the trains start moving, but that seems a bit silly and unnecessary.
Using the three-note sound for a door chime, on the other hand, makes sense. It's a pleasant sound, instantly recognizable, and has a bit of heritage value, I'd argue.
Assuming the STM sticks with this sound for its new trains, we won't have to worry about doo-doo-doo going the way of the dodo.
UPDATE (Aug. 13): I happened to be on the train that's testing this new chime. The doors begin closing at the word "fermons" in "nous fermons les portes," which on the plus side means there's little additional delay caused by adding the warning, but on the minus side means that by the time someone who hasn't heard the notice understands what it says (by the time it gets to the keyword "portes"), it's already obvious that the doors are closing, and the warning becomes unnecessary.
I kind of agree with the commenters below: keep the chime, but lose the voice.
UPDATE (Nov. 12): I was on this train again today, and noticed that they've done exactly as I and others have suggested. The sound remains the same, but the voice announcement has disappeared completely.