A few years ago I used adobe audition to pitch bend up two semi tones (and remove backgound noise), then used virtual cable software to feed the audio output into obs. The original audio also fed into ch. I think had to add a video delay in obs for them to sync back up again, but it worked. The "virtual cable" software basically acted like a speaker and microphone. It appeared in the list of speakers and microphones, then any sound sent to that speaker was available via the microphone.