There is a recording which contains very noisy voice. (voice with a low Signal-to-Noise ratio).
It is a female voice of a stationary speaker (right in front of the microphone) and there are many other recordings of the same speaker with much better quality.
What can be done to denoise the audio?
From the other recordings, it might be possible to extract statistical values that allow some model to filter the speaker's voice.
Existing questions only address snoring, have non-random noise, want to identify a specific artifact or a moving speaker. The question is-it-possible-to-filter-out-a-persons-voice-out-of-100-of-other-voices is similar, but the answer there lacks details and is more about distinguishing, less about extraction.
Some of the tapes are direct copies, some are copies of copies, which have also been recorded using a lower speed setting (4.75 cm/s). This affected the quality prior to digitalization.