So there are these mysterious shortwave radio frequencies in use worldwide called “Numbers Stations.” They usually broadcast a single voice reading off strings of numbers for just a few minutes each day, sometimes preceeded by a short clip of music. Let me tell ya dude, those broadcasts sound positively spooky if you don’t know what they are.

Here’s a RealAudio clip of just one recording. [more] I guarantee that if you tuned this in on your radio late one night, it would scare the holy hell out of you.

It is now generally understood that these broadcasts, heard now for more than 40 years, are actually one-way transmissions containing coded information meant for the ears of international spies.

I am not making this up.

There is a company that sells a four-CD set full of these recordings.

NPR even did a story on them a few years ago.

So why have I not heard of them until now?