Rolling code inverted speech

I have a recording that I can hear a faint conversation in and I’ve tried everything to clean it up I’ve been doing some research and I believe maybe the person was using Rolling code inverted speech. Can anyone help me bring this voice to the surface?This is very important to me and I would be forever in your debt if you were smart enough to crack whatever code is being used in this or just give me your opinion of what is on this recording.