An audiobook is made in four basic steps:
1. A voice actor records the narration for the book.
2. The editor takes the raw audio recordings and edits these files for pacing, flow, and aesthetic flavor. The editor also makes note of any errors in the narration which require a re-record.
3. After making all re-records and inserting the new audio, the audio is listened through one more time. They call this a "QC pass."
4. Finally, the QC'd audio is mastered and encoded for delivery.
I was the owner of step two for all Audible Studios productions.