Breaking Down Amazon's Technical Requirements for Audiobooks

Updated: Apr 6

Audio books are a great way to further monetize your recently published book or ebook, but it takes a lot of additional work. Will you narrate it yourself, or contract a narrator? Will you attempt recording it all from home, or work with a studio or audiobook producer? Are there sections of content from your original book that might not translate well in audiobook form? What will the final “deliverables'' even look like?

Whether self-publishing or working with recording professionals, one thing is certain: Amazon ACX (the platform you need to submit your audio files to if you want to sell on Audible/Amazon/iTunes) is very strict about the technical requirements of the audio files you eventually upload. According to Amazon:

The ACX Quality Assurance team may reject titles that do not meet these standards, and their retail release may be delayed.

For those of you who are contemplating creating an audio book, or are in the middle of the process, here’s a helpful breakdown of Amazon ACX’s technical requirements for audio books:

Your submitted audiobook must:

1. “ consistent in overall sound and formatting”

Your tone, audio levels, pacing, and audio quality needs to be consistent throughout the entirety of the audio book. Good recording performances go a long way and editing tools like compression, equalizing, noise reduction, and manual volume adjustments will be needed to achieve consistency.

2. “ free of extraneous sounds”

Unwanted sounds are the equivalent of typos in a traditional book. Extraneous sounds include plosives, mic pops, mouse clicks, excessive mouth noise, and outtakes. Is your recording environment fully isolated, free from background noise? A poorly-recorded audio book is very unlikely to be approved by Amazon. For a successful audio book recording you need an isolated and acoustically treated recording space with a Superior audio engineer who can remove any unwanted noise during the mix.

3. “...include opening and closing credits”

For the opening credits, you or the narrator needs to state the title of the book, the subtitle (if applicable), “written by [author name]” and “narrated by [narrator name].” For closing credits, the only requirement is stating “the end.” You can choose to include more content within these opening and closing credits if desired.

4. “ comprised of ALL mono or stereo files”

This one is easy. Whether you choose to record in mono or stereo, just make sure all your files are consistent. ACX prefers mono files be sent in, but stereo files are accepted.

5. “...include a retail audio sample that is between one and five minutes long”

The audio sample is what the customer hears when previewing your book. It shouldn’t contain any explicit material and should make people want to listen to your audiobook! If your title isn’t self-explanatory, here's your chance to summarize your content and give listeners a teaser of what they’re in for. The preview must be between 1 to 5 minutes.

Each uploaded audio file must:

1. “...contain only one chapter/section per file’

Each chapter or section must be uploaded individually including the opening and closing credits [see rule #3]. This seems a little unnecessary however it allows listeners to move forward and backward throughout chapters or sections of your audiobook easily. Depending on how many chapters your book has you will probably have a lot of files to upload.

2. “... contain the section header read aloud”

You must announce every section or chapter header exactly how it is written within your manuscript. Ex. Prologue, Chapter 1, Section 1, etc. This allows listeners to know what chapter or section they are listening to without ever having to look at their audio player.

3. “...have a running time no longer than 120 minutes”

Each chapter should not exceed 120 minutes. If it does break it up! Add another chapter or section to your audiobook or even a continuation such as “Chapter 1 continued.”

4. "...have room tone at the beginning and end and be free of extraneous sounds”

Each chapter should have no more than 5 seconds of room tone at the beginning and end. Room tone is the sound of an empty room or in other words silence. This space gives listeners their cue that the chapter or section is beginning or ending. Extraneous is another word for unwanted. Files must be free of unwanted sounds such as mouse clicks, mouth noise, the fan on your laptop, etc.

5. “...measure between -23dB and -18dB RMS and have -3dB peak values and a maximum -60dB noise floor”

The volume must range between -23dB and -18dB so listeners can avoid constantly adjusting their volume on their audio players. To reduce the risk of distortion and poor quality audio the peak values must be no higher than -3dB. Background noise can make it difficult for listeners to enjoy the audiobook and therefore there is a limit of -60dB noise floor.

6. “ a 192kbps or higher 44.1kHz MP3, Constant Bit Rate (CBR)”

Titles are encoded in a few different formats that allows listeners to choose and download from the Audible store. To ensure the encoding process will work without errors files must be 192 kbps or higher or Constant Bit Rate MP3 files.

7. “ narrated by a human”

AI seems to be the way of the future but not for audiobooks…yet. Automated or text-to-speech recordings are not accepted. Narrate your audiobook yourself or find a third-party narrator. Check out our tips on choosing a narrator on our Audiobooks page.


Things to consider:

Review your recordings, review all recording files and again review. Sending files with missing requirements will result in your files being sent right back to you for revision. Don’t delay the release of your title, review everything before sending it to ACX.

Ask your family and friends to help you review that way you can get input, support and praise on your creative work before it’s released while ensuring all the requirements are met to be accepted by ACX.

Don’t stress about the long list of requirements and book your recording session with PSS. We’ll take care of everything so you can focus on narrating or finding a narrator to bring your audiobook to life. Download our free ACX Checklist to make sure you've checked off every last requirement to be accepted.

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