Just interested, to what extent can the quality of audio be improved?
I’ve tried a couple of times to remove background amplifier noise from speech in Audition, but it always led to some distortions in speech.
Another time I tried to recover audio written with recorder sensivity set to minimum. It had dynamic range of just one bit, so high amplitudes were modulated by 1-bit impulse trains - but could not demodulate that to a comfortable level of understanding.