beginner seeks advice for raising sub 500hz voice files

[Adam J Greenberg]

I have mono recordings that payback fine, but when only below 500hz is selected a completely different conversation is happening.

Selecting the sub 500hz range makes the hidden conversation playback decent results, but the voices are muddled somehow.

Any suggestions for how to get them sounding better? I've played around with tools and effects but have not found "the" fix for this.

SAMPLE ATTACHED

Thanks for any suggestions  

[SteveG_AudioMasters_]

Suggestion is to give up, I'm afraid. There is no audio above 600Hz of any significance at all (what there is is all caused by clipping at some stage), and since that's where all of the useful information in the human voice is - between a few hundred Hz and 6-7kHz - and as that doesn't exist in this recording, then there's no fix possible. This looks as though it was either recorded on a very cheap cassette recorder that wasn't functioning properly, or, because of the sharp frequency cut-off, it's been resampled very poorly.

[Adam J Greenberg]

Thank you for responding.

I have the original full spectrum recording, I selected the 500hz area and saved it (sample) as thats where the voices can be heard, choosing anything higher than 500hz and the voices above that completely "cover" whats being said. Literaly played normally, the recording is a completly different event compared to what is heard below 500hz...  

[SteveG_AudioMasters_]

No, you cannot hear voices clearly below 500Hz, whatever you claim. Even if there were voices in tha background, they'd have a frequency range that's the same as any other voice, so you've cut them off completely too.