For years I have admired this effect and haven't really been able to replicate it...
Here it starts at 1:00 minute. (sorry, it's more at 57 s.)
This one starts at 0:38 minutes.
To me these effects seem similar. I tried to do something along the lines of white noise with modulating Filter Freq and Res... But it doesn't get that hollowness... So it might need some distortion as well... But especially in the second example the pitch seems to change a lot too... But if I go the white noise route I seem not to get that... Mmmh...
Please let me know if you have any idea how to get me closer!