What noise floor means
Noise floor is the level of everything present in a recording when nobody's talking: your microphone's own self-noise plus whatever the room adds on top, like a computer fan, distant traffic or air conditioning. It's measured against the same scale as your voice, so a high noise floor doesn't just sit quietly underneath. It competes for headroom and makes aggressive noise reduction more likely to be needed later.
Why true digital silence sounds wrong
Cut a gap so clean it registers as literally zero, and it reads as broken rather than quiet. The ear expects some ambience and notices its sudden absence. This is the same reason an over-aggressive noise gate sounds worse than the noise it's removing: it pumps the room tone in and out with every pause, which is far more distracting than a steady, low background ever was.
A concrete benchmark
ACX, Audible's audiobook standard, requires a noise floor below -60 dB RMS, a useful number even if you're not narrating audiobooks, since it's a genuinely quiet room by most home-recording standards. If you're comfortably under that, it's a useful sign that the background noise is under control, though the actual sound and consistency still matter as much as the number.
For audiobook submissions, noise floor is only one part of the technical standard. See our full ACX loudness requirements guide for RMS and peak limits too.
For audiobook narrators, consistent room tone across long recording sessions matters just as much as hitting the final loudness target. See how Optivox handles audiobook mastering for long-form narration.
Lowering it at the source
As long as a room isn't huge, like a kitchen in a mansion, most spaces will do fine. A good tip is simply to stand in the room and speak or sing out loud, and listen carefully to what the room does with your voice. Does it have reverb? Is there a muffled quality to it? Does it echo? That quick test tells you most of what you need to know before you set anything up.
- Get closer to the mic so you need less gain to reach a normal level.
- Turn off anything with a fan, compressor or spinning motor nearby.
- Add soft furnishings, like curtains, a rug or a duvet behind you, to cut reflections.
Capture it on purpose
A few seconds of genuine silence, mic live and nobody speaking, at the start of every session gives you a clean profile of the room's true noise floor. It's useful for gap filling if you ever need natural-sounding room tone in an edit, and it gives noise reduction tools an honest fingerprint to work from instead of guessing.
Optivox measures your noise floor before it touches anything
Rather than applying the same cleanup to every file, Optivox reads the actual noise floor of your recording first, then applies only as much reduction as that particular room and microphone need. It never chases the noise down to an artificial, unnatural silence.