Loudness is the most common purely technical reason a finished audiobook gets bounced — and the most misunderstood. Your narration can be beautifully recorded, cleanly edited and still rejected, because distribution platforms don’t judge sound with ears: they measure it, file by file, against a delivery specification.
The spec, in plain English
The standard delivery loudness for audiobooks is −18 LUFS integrated with a true-peak ceiling of −3 dB. LUFS is a measure of perceived loudness over the whole file; true peak is the highest instantaneous level once the audio is reconstructed by a player. Together they say: the book should sit at a consistent, comfortable listening level, with enough headroom that nothing clips downstream. This sits inside ACX’s required range for typical narration, and it’s what publishers and platforms commonly specify on delivery sheets.
How books drift off spec
Almost never in one dramatic way. Chapters get exported across weeks of sessions at slightly different levels. A re-recorded chapter comes back hotter than the original ten. A whole book is simply mastered quiet — −24 LUFS narration is very common from home studios. Each file sounds fine on its own; measured against the spec, half the book fails, and listeners notice the seams between chapters even when reviewers don’t.
What correction looks like
Level correction is a solved, verifiable problem — as long as it stays level correction. Our Audiobook Loudness Correction tool does it for you on the spot, so you don’t need to wait. it measures every file, brings anything off-target to −18 LUFS with peaks under −3 dB, then re-measures its own output so you download verified numbers, not hope. Files already on target are returned byte-for-byte unchanged — no pointless re-encode, no quality tax on chapters that were already right.
The caveat nobody prints: noise comes up too
Turning a quiet recording up turns its room noise up with it. If your noise floor is borderline, correcting the loudness can push the hiss past a platform’s limit — that’s physics, not a software failing, and any tool that claims to fix loudness and noise in one automatic pass deserves suspicion. The honest workflow: measure first. Our free compliance report shows the noise floor of every file in your book before you spend anything, so you know whether you need level correction, or a quieter recording.
The economics
Correction is priced as the utility it is: £9 per audio-hour, minimum £15 — a 10-hour book is £90 — and the first 20 minutes of any book are corrected free so you can verify the result on your own narration first.