ACX check for your audiobook chapters
Drop your files here and see in seconds whether they meet the technical requirements of ACX (Audible): levels, peaks, noise floor, room tone and format.
Your recording never leaves your computer.
No upload, no account, nothing is stored: the check runs entirely in your browser. It works offline too.
- No upload
- No account
- Works offline
SoloBooth checks this on every delivery, brings each chapter to the ACX values and fills the gaps with room tone.
Get startedOpen StudioWhat is checked
- Format
- WAV or FLAC; MP3 at 192 kbps CBR or higher
- Sample rate
- 44.1 kHz or higher (MP3: exactly 44.1 kHz)
- Channels
- mono or stereo, the same in every file
- Length
- no more than 120 minutes per file
- Average level (RMS)
- −23 to −18 dB
- Peak
- no higher than −3 dB
- Noise floor
- no higher than −60 dB
- Room tone at the start
- 0.5 to 1 second
- Room tone at the end
- 1 to 5 seconds
What you check yourself
- One file per chapter, starting with the chapter title.
- Opening and closing credits as separate files.
- Retail sample: 1 to 5 minutes, without the opening credits, uploaded separately on ACX.
- Consistent sound and volume across all chapters.
- No background noise, mouth clicks, loud breaths or editing errors – only an ear can catch those.
Measured like ACX Check in Audacity: RMS across the whole file, noise floor in the quietest half second. The values are a guide; ACX decides on acceptance. Very long MP3 and FLAC files need a lot of memory in some browsers; WAV is always read in pieces.
From recording to finished delivery.
In SoloBooth you record paragraph by paragraph, edit in the browser and export each chapter to the ACX requirements – spoken by you, stored in Switzerland.
Get startedOpen Studio