IIRC I made the original files with Audacity, although there have been some modifications to them since. You can do a similar effect by doing something like this:
- Add some static noise
- Use a compressor to even out the volume
- Either amplify the track so much that it starts clipping or use the Limiter effect with Hard Clipping
- Add some reverb
The MTF voice effect was done almost the same way, except that the voice is on two layers and the pitch of the second layer is 3 whole tones
lower than the first.