- Use an analogue synthesiser and set the Oscillator wave to White Noise
- Put a Flanger effect and set a slow LFO on the flanger
- Put a Phaser effect and set a slow LFO on the Phase
- Optionally play with the frequencies on the effect or set an LFO on the virtual synth as well
Example in Ableton Live done with Operator – click on picture for zoom in.