For enhancing audio tracks ffmpeg got a lots of filters including:
One can try them like:
ffplay -i <input file> -af afftdn=nf=-20 -af "highpass=f=600, lowpass=f=5000" -af "loudnorm"
and then use as:
ffmpeg -i <input file> -af afftdn=nf=-20 -af "highpass=f=600, lowpass=f=5000" -af "loudnorm" <output file>