WarpMyMind

If I have a file, that has a barely audible message masked under rain and a binaural beat, how do I with the help of Audicity (or some other sound editor) filter out the other noise and hear the script only. is it even possible?

Well, the first thing you could do is filter out the frequency of the binaural beat with an equalizer. This obviously comes with the risk of data/comprehensibility loss, but it's a start. Rain probably has a wider variety of frequencies, and might be more difficult to remove for that reason. Anyways, I'm not really an expert on audio signal manipulation, but it should be a start.

Just a suggestion, but have you tried to write the author of the recording and asking?