The silence at each end
Drop a chapter and see how many seconds of room tone it has at the head and at the tail, measured against ACX and the other audiobook platforms. If an end is short or too long, this tops it up with your own room or trims it, and changes nothing else. Your recording never leaves this tab — the tools on this site never upload your audio.
No file to hand? Try a sample chapter:
Eleven seconds, synthesized by this site rather than recorded, so nobody’s voice is in it.
Ready.
What the platforms ask for
Each range below is the platform’s own. Some state the minimum as a requirement, some as a recommendation; the tool reports both, and the fix aims inside the range either way.
| Platform | Head | Tail | How they put it |
|---|---|---|---|
| ACX / Audible | 1–5 s | 1–5 s | Recommended at both ends; the five-second ceiling is a rule |
| Voices by INaudio | 0.5–1 s | 1–5 s | Stated as a requirement |
| Spotify for Authors | 0.5–1 s | 1–5 s | Listed under “Recommended qualities” |
| Author’s Republic | 1–5 s | 1–5 s | Listed among their requirements |
“We recommend between 1 and 5 seconds of room tone at the beginning and end of each file for an ideal listening experience. Room tone spacing must not exceed 5 seconds.”
— ACX audio submission requirements. The INaudio and Spotify rows come from Voices by INaudio’s technical requirements and Spotify for Authors; all of them are compared side by side on requirements by platform.
How it works
Every recording space has a sound of its own — the building, the air, the microphone’s own hiss. That is room tone. A chapter that opens on it sounds like a room someone is about to speak in; a chapter that opens on digital zero sounds like a gap, and the room arriving with the first word sounds like an edit.
The file is read in tenths of a second from each end. Every tenth that sits at least 25 dB below your own speech level counts as room tone, and the count stops at the first one louder than that — a breath, a page turn or the first word. It is the same measurement the chapter checker uses.
Missing tone is built from the quietest half second of your recording, repeated back and forth so the repeat has no click, and cross-faded into the first word. If the recording has no pause that quiet, the page says so rather than padding with nothing.
An end that runs over the limit is cut back to just inside it. Each end lands a quarter of a second inside its range rather than on the edge, because a fix aimed exactly at “one second” can measure 0.9 afterwards. Levels and noise are left as they are; the result is a 192 kbps MP3 at the file’s own sample rate, measured again from its own bytes before you can download it.
Getting it right while recording
Stay still for a few seconds before you start reading and after you finish, with the recorder running. That stretch is the tone an editor copies when a pause has to be lengthened or a cut needs covering. The room test tells you whether the room itself is quiet enough first.
Room tone is one of the numbers ACX looks at. The chapter checker measures the rest — level, peaks, noise floor, format — and fixes what can be fixed, and the batch checker runs a whole book at once.
Straight answers
The sound of your recording space with nobody speaking: the building, the air, the microphone's own hiss. In an audiobook it sits at the start and end of every chapter and in the pauses between sentences, so the recording never drops into absolute digital silence.
ACX recommends between one and five seconds of room tone at the beginning and end of each file, and says room tone spacing must not exceed five seconds. Voices by INaudio and Spotify for Authors ask for half a second to one second at the head and one to five seconds at the tail. The table on this page checks your file against each of them.
It counts the tenths of a second at each end that sit at least 25 dB below your own speech level, stopping at the first sound louder than that. It is the same measurement the chapter checker uses, so a file cannot measure one way here and another way there.
Silence is not room tone. A listener hears the room vanish and come back with the first word, which sounds like an edit. When an end is short, this page builds the missing tone from a quiet half second of your own recording and cross-fades the seam; when the recording has no pause that quiet, it says so instead of padding with nothing.
Only the two ends. Tone is added where an end is short and removed where it is long, landing just inside the range rather than at its edge, then the file is encoded as a 192 kbps MP3 at its own sample rate and measured again before you can download it. Levels, noise and everything between the first and last word are left alone; the chapter fixer handles those.
No. The file is read, measured, edited and encoded inside this browser tab. The tools on this site never upload your audio.
Sources: the ACX audio submission requirements, Voices by INaudio technical requirements and Spotify for Authors, uploading audiobooks.