Yup… Take the bad audio

Yup… Take the bad audio along with the video to the interviewee, play it several times, and have them practice saying it in sync with the original. You can always put headphones on them so they can listen to the original while you’re recording them speaking the lines. Run your audio recorder, the entire time – even while they’re practicing,as you never know when they’re going to nail it. Have them run through it several times.

In post, break the sentences down to a few words at a time. Locate the closest match to each part, then do some minor cutting and tweaking to sync up the new audio. Many tv shows and movies have the actors overdub their own voice to brief scenes, where ambient noise or other factors may have rendered the original audio unusable.