When you publish an audiobook, platforms like Audible and ACX require your files to follow certain technical and formatting standards. These rules make sure your book is easy to navigate, pleasant to listen to, and works across all devices.

Narrator includes an ACX Validation tool that checks your work and fixes many common issues automatically — but it’s important to understand the basics.

1. Chapters & Headings

• Each audiobook must have a separate file for each chapter or section.

• To make this possible, your manuscript must use Headings (H1) for chapter titles.

👉 In Word: Select your chapter title → Home → Styles → Heading 1.
👉 In Pages: Select your chapter title → Format sidebar → Style → Heading.

⚠️ Bold or larger text isn’t enough — you must use actual heading styles so Narrator can recognize chapters.

2. Technical Audio Specs

ACX requires:

• RMS (loudness): –23 dB to –18 dB

• Peak level: no higher than –3 dB

• Noise floor: below –60 dB

• Format: 192 kbps MP3, 44.1 kHz, constant bit rate, mono or stereo

These standards prevent distortion, keep background noise under control, and ensure playback compatibility.

3. Front and Back Matter

• Opening credits: Title, subtitle, author, narrator

• Closing credits: “The End” or similar

• Retail sample: 1–5 minutes, representative of the audiobook

4. Required Pauses

• Start of each file: 0.5–1 second of room tone

• End of each file: 1–5 seconds of room tone

This ensures clean transitions and prevents playback from starting or ending abruptly.

5. Listening Quality

Even if files pass technical checks, ACX reviewers listen for:

• Consistent tone and pacing

• Clean edits without clicks or repeats

• Clear narration without missing text

How Narrator’s ACX Validation Tool Helps

Once your manuscript and chapters are set up correctly, Narrator will:

• Adjust RMS levels automatically

• Apply noise reduction if needed

• Add a limiter to control peaks

• Check silence at chapter beginnings and endings

• Correct Nav points (chapter markers) if they’re slightly out of place

• Ensure the right export format for ACX

👉 As long as you’ve set your headings properly and left basic pauses, Narrator takes care of the rest — saving you time and ensuring your files meet ACX standards.ACX Recommendations — and How Narrator Helps You Meet Them