You're a KGB agent currently in Russia who had experience with weird email.
Now, you had received an envelope from the front of your door with the following:
- A letter saying "Fly to this airport."
- A tape
You sighed. Passport, check. Visa? You can steal your neighbour's and forge it. If you need to use any electronics, you realized that you can buy a transformer at a home depot.
The first ever audio steganography in this site requires heavy programming skill. The only thing you need is a simple audio player, like the one I provided.
It has been identified that the tones consists of sine wave, square wave & sawtooth wave.
The letter said "Go to this airport," so intuitively the answer will ask the KGB agent to go to an airport, not a city(ie. Glasglow =D)