I have recently learned of a tool where you can listen in on shortwave radio online. This can be found here and is very intuitive. What is even cooler is why you should care.
number stations were first found in the aftermath of WW2. The transmission points are known, but no nation has formally acknowledged it. There are a few still in action today. While mostly used by former Soviet states, North Korea and the UK still have operational number stations. They will, at set intervals, read a series of seeminly random numbers. The best guess of the function is to communicate with spies in the field to whom the numbers have meaning. Or perhaps the numbers, like the original enigma machine, are the key for an encrypted message. Either way these are cool as hell.
Here is a recording of a number station out of NK:
