After listening to it for many times, you'll start noticing it repeat from a lower octave around 6 seconds into the audio, and the higher octave fade out, making the illusion of higher increments.

There is a website out there somewhere I went to once. It has audio and visual tricks. One was a mono recording from inside an artificial head and it has true three dimensional qualities. Just like the real world. Then there are the freaky audio tricks, one could make you puke. Some weird science out there!

sounds like wheel of fortune theme song bits slowed down