The basic noise removal left something to be desired, so I worked through documentation to come up with a more thorough cleaning process in Audacity.
- Use Analyze > Plot Spectrum to identify any specific whine frequency. The example below was based on an 800 Hz frequency.
- In Effect > Nyquist Prompt, remove the offending frequency:
(setf freq 800)
(setf q .7)
(if (arrayp s) (vector (notch2 (aref s 0) freq q) (notch2 (aref s 1) freq q)) (notch2 s freq q))
- Effect > Leveller, with settings "Moderate" and "-55 dB"
- Effect > Amplify (adjust the volume as necessary)
- Effect > Noise Removal (same process as before)