All through the night, you could hear it in the fog

Image source: http://picasaweb.google.com/Keeches/LogOfFayaway#

All through the night, you could hear it in the fog.

Like the calls of great, strange whales -- deep and mournful -- the horns of the ships were each unique.  Some seemed like they were already aground, bellowing in anger, others much more distant -- sailing through the night to Spain, Scandinavia, and France and calling out to far away travellers.

How far away would a ship have to be before it could no longer be heard?  Do the ice crystals suspended in a fog help a sound travel better, or would it muffle the sound instead?

The cruise liners and the cross-channel ferries and the fishing boats continued their solitary journeys all night, periodically calling and warning with their fog horns.