You may be interested in this. Generally Dithering may be important in your case.
Maybe these settings help you for starting:
sox input.wav -b 8 output.wav gain -1 rate 8000 dither -s
Domanda
I can´t get this audio clean, So I don´t now what to do. I hace tried cleaning it, Transforming on various kinds of formats.
Altri suggerimenti
Open this sound in Audacity, convert to 80 kHz and apply noise filter on correct level.