Identify the dominant noise
Listen for a constant hum, sudden interruptions or reverberation. Different problems need different treatment, and aggressive filtering can make speech sound metallic.
Protect the voice first
Use noise reduction gently, then compare the result with the original. The goal is intelligibility and a stable voice, not complete silence between words.
Check captions after cleanup
Audio processing can change how words are recognized. Regenerate or review captions after cleanup so the text matches the final soundtrack.
Test on phone speakers
Headphones can hide problems. Play the export on a phone at a normal volume and listen for missing consonants, pumping or distracting artifacts.