Audiobook file checker
Drop in your chapter files and see, before you upload, whether they'll pass ACX, Google Play Books, Kobo and Spotify for Authors: volume, peaks, background noise, room tone, bit rate and sample rate, file by file.
Your files are checked in your browser. Nothing is uploaded to Bervet and nothing is kept. Free for members.
| File | Length | Format | RMS | Peak | Noise floor | Room tone (start / end) | Platforms |
|---|
Room tone is measured as the stretch at the start and end that stays near the file's quietest level. If a number looks wrong, listen to the start and end of that file.
What each platform asks for
From each platform's own pages, checked 4 October 2026.
ACX (Audible, Amazon and Apple Books through ACX)
- MP3, 192 kbps or higher, constant bit rate (CBR), 44.1 kHz.
- Volume between -23 dB and -18 dB RMS.
- Peaks less than -3 dB.
- Noise floor less than -60 dB RMS.
- Every file in mono, or every file in stereo.
- 1 to 5 seconds of room tone at the start and end of each file is recommended; gaps no longer than 5 seconds.
- Each file no longer than 120 minutes; one chapter or section per file.
Google Play Books
- MP3, AAC (M4A), FLAC or WAV.
- MP3 or AAC: 128 kbps or more for mono, 256 kbps or more for stereo; constant bit rate preferred.
- FLAC or WAV: 16 bits per sample, 44.1 kHz or higher.
- The whole audiobook between 5 minutes and 100 hours.
Voices by INaudio (formerly Findaway Voices)
INaudio keeps its technical requirements inside your Voices account, so they aren't listed here. Check them there before you upload.
What the numbers mean
RMS is the average loudness of the whole file. Peak is the single loudest moment: too high and it can distort. Noise floor is how loud the room is when nobody's speaking, measured over the quietest half-second. Room tone is the quiet at the start and end of each file.
Written a book? List it free.
Your cover, blurb and store links, a first chapter readers can try, and numbers on where they stop. Host your advance copies free too.