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Noise Floor Meter

Find out how quiet your recording space really is, measured the way ACX measures it, with your own mic. Nothing is recorded or uploaded.

  • Free
  • No upload
  • No sign-up

How quiet is your room?

Set your microphone up as you record, with the same gain, then start. Nothing is recorded or sent anywhere: only the level is measured, live, on your device.

Where it runs

Works in a current Chrome, Edge, Firefox or Safari, on Windows, Mac, Linux and Chromebook computers, Android phones, iPhones and iPads. Nothing to install, no account.

Needs a microphone, and your permission to use it. Nothing it hears leaves the page.

How to use it

4 simple steps.

  1. 01

    Allow the microphone

    Pick the mic you narrate with. Nothing is recorded or uploaded; the level is measured live.

  2. 02

    Stay silent

    Sit still for ten seconds while the meter listens to your room with every browser filter switched off.

  3. 03

    Read a line

    Read the sample sentence at your normal narrating volume, at your normal distance from the mic.

  4. 04

    Get the verdict

    See your noise floor, how far your voice sits above it, and whether it will pass ACX’s −60 dB after mastering.

How the meter measures your room

The meter reads your microphone in 100 ms blocks, with the browser’s noise suppression, echo cancellation and automatic gain switched off, and keeps three numbers:

  • Level: the RMS level right now, in dBFS.
  • Peak: the highest sample since you started.
  • Noise floor: the RMS level of the quietest half-second, which is how ACX measures it.

Why the room alone isn’t the whole story

Mastering brings your narration to about −20 dB RMS, and the room is raised or lowered with it. A room at −70 dB with a voice at −30 dB ends at −60 dB after mastering, a borderline pass. The same room with a voice at −18 dB ends at −72 dB. The guided test measures both and shows the floor you can expect after mastering.

Noise floorWhat it means
−66 dB or lowerStudio quiet: plenty of headroom.
−66 to −60 dBPasses ACX.
−60 to −57 dBClose: quieten the room or move closer to the mic.
Above −57 dBToo noisy for ACX without changes.

Already recorded? The ACX checker measures the noise floor of your files, and ACX mastering can turn noisy pauses down. audiobook.tools is not affiliated with ACX or Audible.

FAQ

Questions, answered.

What is a noise floor?

The level of everything your microphone hears when nobody is speaking: computer fans, traffic, the fridge, the hum of the mic itself. ACX measures it as the RMS level of the quietest half-second of a file and asks for −60 dB or lower.

Why does the meter ask me to read a sentence?

Turning your mic gain up raises your voice and the room by the same amount, so the room on its own says little. What survives mastering is the gap between them: once your voice is brought to −20 dB RMS, the room needs to sit at least 40 dB under it to pass.

Is this as accurate as a sound level meter?

It measures digital level (dBFS) from your own mic and interface, which is exactly what ACX checks in your files, so it is the right number for audiobooks. It does not measure acoustic loudness (dB SPL) and differs between devices.

Why turn off noise suppression?

Browsers clean up calls with noise suppression, echo cancellation and automatic gain. They would make your room sound quieter than your recordings will, so the meter switches all three off. Turn off any “voice isolation” or enhancement setting your computer adds too.

My room fails. What helps most?

Turn off fans, heating and fridges while you record, move away from windows and computers, and hang soft furnishings or blankets around you. Speaking a little closer to the mic raises your voice above the room. ACX mastering can turn the pauses down, but a quieter room always sounds better.

Is my microphone recorded?

No. Levels are calculated inside your browser and nothing is saved, recorded or sent anywhere.

Read the guide

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