# Mastering for Audiobooks and Spoken Word > Audiobook mastering follows entirely different rules than music -- strict loudness consistency, noise floor requirements, and no room for creative dynamics. [All guides](/blog) # Mastering for Audiobooks and Spoken Word Published 8 September 2026, 08:00 UTC · updated 31 August 2026, 13:05 UTC · by Loopin Audiobook mastering has almost nothing in common with music mastering — the goal is strict, boring consistency, not creative dynamics. Distributors like ACX have specific technical requirements, and missing them gets a submission rejected outright. ## Loudness consistency matters more than the specific target Unlike music, where dynamic range is often desirable, audiobook narration needs to sit at a very consistent level throughout — a listener shouldn't have to adjust volume between chapters or even between sentences. ACX, a major audiobook platform, specifies RMS levels between roughly −23 and −18 dB, with peak values under −3 dB. Check your specific distributor's exact technical requirements before finalizing, since these numbers can differ from platform to platform and get enforced strictly on submission. ## Noise floor requirements are strict Audiobook platforms typically require a very low noise floor — often −60 dB RMS or quieter — measured during silent passages between sentences. Any hum, hiss, or room noise that would be inaudible in music becomes a rejection reason here. This makes the recording environment more important than usual; heavy noise reduction to fix a noisy recording after the fact often introduces its own artifacts that create new problems during review. ## Compress for evenness, not impact Narration needs firm, consistent compression to keep every word at a similar perceived level — this is one of the few contexts where fairly heavy compression, by music standards, is entirely appropriate and expected. The goal is a recording where a listener never needs to touch the volume control, regardless of whether the narrator is speaking quietly or with more emphasis. ## Remove mouth noise and breath sounds carefully Clicks, pops, and heavy breath sounds are far more noticeable in spoken word than in music, where instruments mask them. Editing these out, or reducing breath sounds specifically, is standard practice for audiobook production in a way it generally isn't for music mastering. Be careful not to remove every breath entirely — completely breath-free narration can sound unnaturally robotic. Reduce rather than eliminate. ## Check requirements before you start, not after Different platforms have different exact specifications for RMS level, peak level, noise floor, and file format — check yours before recording and mastering, since it's much easier to hit a target from the start than to fix a finished master that falls outside spec after the fact. Rejection for a technical spec issue, rather than content quality, is a common and avoidable delay in audiobook submission. ## Frequently asked questions ### What RMS level do audiobook platforms typically require? ACX, a major platform, specifies RMS levels roughly between -23 and -18 dB with peaks under -3 dB. Requirements vary by platform, so check your specific distributor's current spec before finalizing. ### How quiet does the noise floor need to be for an audiobook? Often -60 dB RMS or quieter during silent passages between sentences. This is much stricter than music mastering and makes a clean recording environment more important than fixing noise afterward. ### Should I remove all breath sounds from narration? No, reduce rather than eliminate them. Completely breath-free narration can sound unnaturally robotic -- the goal is consistency and clarity, not the total removal of natural vocal sounds. ## Related reads - [Master your track free](/mastering) - [How to master a spoken word track](/blog/how-to-master-a-spoken-word-track) - [What is LUFS?](/mastering/what-is-lufs) --- Source: https://onloopin.com/blog/mastering-for-audiobooks