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How quiet is the sound of air molecules?

−24 to −23dBanywhere in still air at room temperature

The random jostling of air molecules (Brownian motion) produces a tiny pressure noise estimated at about -23 to -24 dB. BBC Future puts it at about -24 decibels at room temperature and Microsoft at -23 dB, which is why even the best anechoic chambers cannot get much quieter than about -25 dB.

Level
−24 to −23 dBunweighted sound level
Daily limit
No daily limitNIOSH, at the loud end

What the numbers mean

How it was measured. Theoretical noise floor from the random motion of air molecules, not a measurement of a sound source. BBC Future gives about -24 decibels at room temperature; Microsoft gives -23 dB. Weighting not stated.

Sound is a pressure fluctuation, and air molecules are never perfectly still. Their random collisions create a very faint, constant pressure noise. Microsoft describes Brownian motion, the movement of particles in a gas or liquid, as the quietest sound theorised, with only a vacuum beyond it.

The estimates are about -23 dB (Microsoft) and about -24 dB (BBC Future, for air at room temperature). These numbers sit well below the nominal threshold of human hearing at 0 dB, so no one can hear this noise.

It matters as a floor. Microsoft's chamber measured about -20 dB in 2015 and Orfield Laboratories' chamber -24.9 dBA in 2021, both close to the level BBC Future gives for air itself.

Is it safe?

Below 85 dBA, the level NIOSH allows for a full 8-hour day. (This figure is not A-weighted; treat it as a rough guide.) At this level, sound is not a hearing risk however long it lasts, though it can still disturb sleep or concentration.

Protecting your hearing

Nothing to protect against: this is far below anything the ear can detect.

Earplug and earmuff ratings (NRR in the US, SNR in the UK and EU) are lab figures; real-world protection is usually lower. How to read the ratings.

Compared with sounds nearby

Using midpoints of each range. Energy multiplies by 10 every 10 dB; perceived loudness roughly doubles (why).

  • Threshold of hearing (0 dB): it has about 224× the sound energy of this and sounds about 5.1× as loud.
  • Normal breathing (10 dB): it has about 2,239× the sound energy of this and sounds about 10.2× as loud.

Questions

What is the quietest sound possible in air?

The noise of air molecules colliding, estimated at about -24 decibels at room temperature (BBC Future) or -23 dB (Microsoft). Only a vacuum, which carries no sound at all, is quieter.

Can you hear Brownian motion?

No. At around -23 to -24 dB it is far below 0 dB, the nominal threshold of human hearing.

Sources

  1. Inside the quietest place on Earth, BBC Future. Supports: dB_low: about -24 dB.the noise produced by air molecules colliding with each other at room temperature is estimated to be about -24 decibelsChecked 2026-11-02.
  2. Audio Lab | Microsoft: Inside B87, Microsoft. Supports: dB_high: -23 dB.Brownian Motion -23dBChecked 2026-11-02.
  3. Audio Lab | Microsoft: Inside B87, Microsoft. Supports: body: definition.The quietest sound theorized by mathematicians is Brownian motion: the movement of particles in a gas or liquid.Checked 2026-11-02.

This page is general information, not medical advice. If you have ringing in your ears, muffled hearing or any change in your hearing, see an audiologist or your doctor.