If you record or produce audiobooks, the fastest way to lose time is a failed ACX upload. The checks are simple on paper, yet small issues with RMS, true peak, or noise floor can stall a release and create rounds of re-exporting. This guide shows the exact workflow we use to deliver ACX-ready masters on the first pass, with clear timelines and chapter-by-chapter previews in our WorkTracker.
TL;DR — Our Process
- Place order and send files to secure the next available date, then upload chapters.
- Confirm timeline and track progress in a live WorkTracker with time-stamped notes and previews.
- Edit, master, deliver ACX-ready WAV and MP3, plus a QC summary and pass guarantee.
Common ACX Rejection Reasons and How We Fix Them
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Noise floor above −60 dBFS
Usually room noise or gain staging. We apply broadband reduction where it’s safe, add targeted notch or hum removal, and use measured expansion in pauses.
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RMS outside −23 to −18 dBFS
Often uneven edits or limiters set for music, not speech. We reset the dialogue chain, correct gain staging per chapter, and add transparent peak control.
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True peaks over −3 dBFS
Brickwall limiters can hide inter-sample peaks. We set true-peak control correctly and verify with oversampling.
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Inconsistent sound across chapters
Different rooms or sessions. We create a reference profile, match tone and level, and smooth transitions so the listener hears one book, not many sessions.
Prepare Files So Mastering Goes Faster
- Record at 24-bit, 44.1 kHz WAV and keep healthy input gain with headroom.
- Capture a few seconds of room tone in each session.
- Keep one mic, one position, and document settings.
- Export per-chapter files, named consistently (e.g.,
BookTitle_Chapter_01.wav). - Avoid heavy noise reduction or limiting on your side. If in doubt, send it raw and we’ll advise.
Turnaround & Pricing
Turnaround depends on finished hours and current schedule. We provide firm dates at booking, plus rush options when the calendar allows.
- Mastering only: RMS, true peak, and noise floor to spec, with a consistency pass and QC report.
- Edit & Master: light breaths/clicks cleanup, tonal match, ACX-ready masters.