Want To Make An Audiobook For Audible? Read This First
If you want to make an audiobook that can be distributed on platforms like Audible, Amazon and iTunes then read this guide. It explains ACX and the requirements for submitting audio to their platform.
What Is ACX?
ACX, is the acronym for Amazon’s Audiobooks Creation Exchange. This is the hub for creation of audio books that will appear on Audible, the Amazon owned audiobooks platform. Audiobooks uploaded to ACX will be sold on Audible, Amazon and Apple iTunes.
Audible began in 1995 and since inception has created an audio player, the Audible Player, supplied audiobooks books to Apple for the iTunes Store and was eventually acquired by Amazon Inc. in 2008 for $300million.
How To Submit Audio Files To ACX
In order to get an audio book in the Audible store you need to first set up an ACX account and set up a new project. Before any audio can be uploaded you will need to link an existing book on the Amazon store, this will be the print/Kindle version of the book you will be submitting the audio version of.
ACX Requires Consistency
Amazon ACX say “Your submitted audiobook must be consistent in overall sound and formatting. Consistency in audio levels, tone, noise level, spacing, and pronunciation gives the listener an enjoyable experience. Drastic changes can be jarring to the listener and are not reflective of a professional production. This distracts from the listening experience and may lead to poor reviews and reduced sales.”
Choose A Good Microphone
Good audio starts at the source, in this case a good quality voiceover microphone. There’s never been a better time to buy a high quality microphone for this purpose. There’s some great options from brands like Sontronics and PreSonus, here are some resources.
Clean All Audio Files
Any audio professional is going to take care to ensure that the audio is as pristine as possible, however to remove any doubt ACX expect the following quality in all audio. “Each uploaded file must be free of extraneous sounds such as plosives, mic pops, mouse clicks, excessive mouth noise, and outtakes. Extraneous sounds can distract listeners from the story, and outtakes sound unprofessional. Each can elicit bad reviews and bad reviews can hurt sales.”
There are several tools you can use to clean your audio;
Your DAW also has powerful tools you can use such as the audio editor and the included plugins.
ACX File Uploader
Each File Needs Credits
In addition to the text of the book audio files for credits need to be included in the files. This is what ACX say;
Your audiobook must include opening and closing credits that match the title's cover art.
At minimum, the opening credits must note the name of the audiobook, the name of the author(s), and the name of the narrator(s). Closing credits must, at minimum, state "the end".
Opening Credits Minimum Requirements
"[title of audiobook]"
"(subtitle if applicable)"
Written by [name of author]
Narrated by [name of narrator] Closing Credits Minimum Requirements
The End
Include An Audio Sample
ACX say “Your audiobook must include a retail audio sample that is between one and five minutes long. Explicit material is not permitted in the sample. This sample should start with narration, not opening credits or music. The sample must not include explicit material. This sample is used by customers to preview of your audiobook.'“
Upload The Audio In Sections
ACX require each section e.g. forward, Chapter 1, Chapter 2 etc. be uploaded as an individual file. In other words you can’t upload the entire book in one audio file, you must create, edit, mix and then upload each one.
ACX say; “You'll be prompted to upload each file individually. Both the opening credits and closing credits must be separate files. This ensures listeners can easily navigate between sections, and that skipping forwards or backwards moves them forward or back one section.”
Include Room Tone
Don’t leap into record or end record quickly as ACX requires room tone. When editing you will need to ensure this space is left at the front and end of each audio recording. For those who edit dialogue all the time this will feel alien as we are used to editing as close to the audio as possible to reduce room noise. Not in this case. “Each file must have 0.5 to 1 second of room tone at its beginning and 1 to 5 seconds of room tone at its end. This space is required to ensure titles are successfully encoded in the many formats made available to customers. It also gives listeners an audio cue that they have reached the beginning or end of a section.”
Include Audio Cues
When recording make sure you audibly introduce the section you are about to read.
“Each file must contain the section header, if contained within the manuscript (e.g., "Prologue", "Chapter 1", "Chapter 2").
These announcements help the listener understand what section of the book they are listening to without having to look at their player. If a section header is found to be missing during the ACX QA review, you will be contacted to make revisions which could delay the release of your title. Be consistent - a listener may think content is missing if most headers are read but some are not .”
Audio Specification
Each file must be no longer than 120 minutes.
Each file must measure between -23dB and -18dB RMS.
Each file must have peak values no higher than -3dB.
Each file must have a noise floor no higher than -60dB RMS.
Each file must be 192kbps or higher 44.1kHz MP3, Constant Bit Rate (CBR).
ACX explain how the file will be encoded before being put on sale. “Before going on sale in the Audible store, titles are encoded in a variety of formats that customers have the option of downloading. 192kbps (or higher), Constant Bit Rate MP3 files are required so this encoding process works without error. You may upload 256kbps or 320kbps files if you'd like, but the difference in quality heard by listeners will be negligible.“
Note that the ACX format uses RMS as a perceived loudness measurement as opposed to LUFS or LKFS. Audiobooks do not use BS1770 loudness, they use RMS so make sure you can measure RMS. iZotope RX has this feature.
Don’t Mix Channel Widths
ACX recommend mono files but will however accept stereo files, however, you must not mix formats, the entire book must consist of all mono or all stereo. If you try and upload both mono and stereo your files will be rejected.
You Must Use A Real Person
You might think we are joking but ACX requires a human to read the transcript, text to speech etc. is not allowed.
“Your submitted audiobook must be narrated by a human.
Text-to-speech recordings are not allowed. Audible listeners choose audiobooks for the performance of the material, as well as the story. To meet that expectation, your audiobook must be recorded by a human.”
How Can I Be Sure I Get This Right?
ACX has a handy audio analysis tool that checks each audio file as you upload it. If there are any issues it will tell you and ask you to fix them and to resubmit the audio.
ACX Audio Analysis
Summary
ACX is a powerful platform for those wanting to create and distribute their audiobooks, it is well worth checking out.