This sound was made by manipulating the frequency and panning of a sine wave using the Minim sound library in Processing. I found that adjusting the portamento parameter has some strange and interesting results. Certain values for portamento seem to cause the sine wave to degrade into noise when manipulating the frequency of the waveform. I captured several minutes of this noise and then selected a small segment that has some unusual modulation going on.
Minim Sine Wave Experiment