Fog music

The last days have been fairly foggy.

I live very close to the harbor, though I cannot see the Oslo fjord from my apartment.
The ferry from Horten to Moss crosses the Oslo fjord and lets off the trucks, private cars and passengers in Moss harbour.
This also happens in foggy weather.

To make that a little bit safer, they use a fog alarm.
Actually two fog alarms, I am told.
One fog alarm has a fixed place in the harbor and helps the ferry to anchor in the right place.
(Though rumours say they also have more advanced instruments for that.)
The second fog alarm is on the ferry, and is used to warn other ships and boats in the fog that here comes the ferry.
Each fog alarm sounds slightly different.

So here I sit in my home, listening to this fog music.