The ACX Audiobook Standards Checklist

The ACX Audiobook Standards Checklist

A Professional Voice & Production Guide

By Revision Sound

Produce audiobooks that pass ACX review the first time—without guesswork, over-processing, or wasted revisions.

This checklist distills real-world audiobook production practice into a clear, repeatable workflow covering recording, editing, mixing, and mastering—the same approach used by professional narrators and audio engineers.

WHAT THIS CHECKLIST IS (AND ISN’T)

This is:

  • A practical, numbers-based reference

  • Built on ACX requirements + industry norms

  • Designed to be used before you hit record and before you upload

This is not:

  • A gear list

  • A “fix it in post” mentality

  • A music mastering guide (audiobooks are different)

1. RECORDING ENVIRONMENT

ACX Expectation

  • Quiet, controlled space

  • No audible echo, reverb, or environmental noise

Best Practice

  • Small treated room > large untreated room

  • Soft materials behind and around mic

  • Consistent setup every session

2. ROOM TONE REQUIREMENTS

Before Speech

  • 0.5–1.0 seconds of clean room tone before the first word

After Speech

  • 1.0–2.0 seconds of room tone at the end of each file

Session Capture

  • Record 30–60 seconds of room tone per session

  • Never use digital silence

3. MICROPHONE TECHNIQUE

  • Distance: 6–8 inches

  • Slight off-axis placement (10–20°)

  • Fixed posture and head position

  • Avoid dramatic movement or leaning

4. RECORDING LEVELS

While Tracking

  • Peaks: –12 to –6 dBFS

  • Average speech: –18 to –16 dBFS

  • No clipping—ever

Rule: Record conservatively. Gain later.

5. EDITING & CLEANUP

Remove or Reduce

  • Mouth clicks and lip smacks

  • Distracting breaths (not all breaths)

  • Plosives and harsh sibilance

  • Long silences (>3–4 seconds unless intentional)

Natural Pausing

  • Sentence pauses: 0.3–0.6 sec

  • Paragraph breaks: 0.8–1.2 sec

6. NOISE FLOOR

ACX Requirement

  • –60 dBFS or lower

Target

  • –65 to –70 dBFS

Important: Over-processing causes more rejections than light room noise.

7. PROCESSING GUIDELINES

EQ

  • High-pass filter: 70–90 Hz

  • Gentle tonal correction only

Compression

  • Ratio: 2:1–3:1

  • Gain reduction: 2–4 dB max

  • Goal: consistency, not loudness

8. LOUDNESS & MASTERING

ACX Hard Limits

  • RMS: –18 to –23 dBFS

  • Peak: –3 dBFS max

Recommended Target

  • RMS: –20 dBFS

  • True Peak: –3.5 to –4 dBFS

9. EXPORT SETTINGS

  • Format: MP3

  • Bitrate: 192 kbps CBR

  • Sample rate: 44.1 kHz

  • Mono

File Naming

BookTitle_Chapter_01.mp3
(No symbols, no extras)

10. STRUCTURE REQUIREMENTS

  • One file per chapter

  • Opening credits included

  • Closing credits included

  • Retail sample: 1–5 minutes

  • No music or sound effects

11. FINAL QA CHECK

Before upload, confirm:

  • No clipping

  • RMS in spec

  • Peaks below –3 dBFS

  • Noise floor below –60 dBFS

  • Consistent tone across chapters

  • Correct chapter order and naming

COMMON ACX REJECTION TRIGGERS

  • Recording too hot

  • Inconsistent loudness

  • Audible mouth noise

  • Aggressive noise reduction

  • Music-style mastering

  • Peaks exceeding –3 dBFS

THE REVISION SOUND APPROACH

Audiobook production is about clarity, consistency, and restraint.
Meet the spec. Serve the listener. Pass review the first time.

About Revision Sound

Revision Sound provides professional audio production for podcasts, audiobooks, film, TV, and commercial media—focused on storytelling, technical precision, and repeatable workflows.

Related Posts