Indeed,
Even if you do not have the Elbe or Furie, their basic folders are there, as placeholders.
Go to the main Shipsim folder, and go to Actors/Objects/Furie.
There is the horn.wav, the whistle.
You can paste it into any of the other ship folders, but please note; if you overwrite the default horn, you cannot restore it without a fresh install, so backup the horn you replace, if you want to keep it safe.
Or, you can - if you have it installed - use the Horn addon pack installer, that has the option to roll back to the default horns aswell. If you haven't tried this pack yet, then I would recommend it for sure! Same goes for the radio pack.
http://www.shipsim.com/downloads/patches.php
Regards,
Fred