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How quiet is Microsoft's anechoic chamber?

−20.6 to −20.4dBAinside the chamber

Microsoft's anechoic chamber in Building 87, Redmond, measured about -20 dB when Guinness World Records tested it in 2015: -20.35 dBA according to Guinness, -20.6 decibels according to BBC Future. It held the title of quietest place on Earth until Orfield Laboratories reclaimed it with -24.9 dBA in 2021.

Level
−20.6 to −20.4 dBAA-weighted sound level
Daily limit
No daily limitNIOSH, at the loud end
Versus conversation
1/2.0e+2 million energyabout 314.6× quieter

What the numbers mean

How it was measured. Background noise level inside the main anechoic chamber in Building 87 at Microsoft's Redmond headquarters, measured for Guinness World Records in 2015. Guinness gives -20.35 dBA; BBC Future reports -20.6 decibels; Microsoft rounds it to -20 dB.

Microsoft built the chamber in Building 87 to test the equipment its engineers develop; BBC Future says products such as Surface computers, Xbox and HoloLens were developed there. It describes the chamber as a cube 21 ft (6.36 m) on each side, every surface lined with 4 ft (1.2 m) foam wedges, with a floor of steel cables strung like a trampoline net above the wedges.

Most of the quiet comes from isolation. The chamber sits inside six concrete 'onion' layers with walls up to 12 inches thick, which BBC Future says cut outside noise by around 110 decibels. It floats on 68 vibration-damping springs on its own foundation slab, and Microsoft notes the whole room sits on springs separate from the rest of the building.

The sources disagree slightly on the record value. Guinness World Records gives -20.35 dBA, BBC Future -20.6 decibels and Microsoft's own page -20 dB. For context, BBC Future puts the noise of air molecules colliding at room temperature at about -24 decibels, so the room is close to the floor set by the air itself.

Visitors often find it unsettling. Microsoft engineer Hundraj Gopal told BBC Future that people can hear others breathing on the other side of the room and hear stomachs gurgling, and some want out within a few seconds.

Is it safe?

Below 85 dBA, the level NIOSH allows for a full 8-hour day. At this level, sound is not a hearing risk however long it lasts, though it can still disturb sleep or concentration.

Protecting your hearing

No hearing protection is needed. The only risk is discomfort from silence; visitors who feel dizzy should step out.

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).

  • Orfield Labs anechoic chamber (−24.9 dBA): this has about 2.8× its sound energy and sounds about 1.4× as loud.
  • Haleakalā crater (10 dBA): it has about 1,116× the sound energy of this and sounds about 8.3× as loud.
  • Rustling leaves (10–20 dBA): it has about 3,528× the sound energy of this and sounds about 11.7× as loud.
  • Normal conversation (55–70 dBA): conversation has about 2.0e+2 million× the energy of this.

Questions

Is Microsoft's chamber still the quietest place on Earth?

No. It took the Guinness record in 2015 at -20.35 dBA, but Guinness World Records now lists Orfield Laboratories in Minneapolis at -24.9 dBA, measured in 2021.

Why is it so quiet?

Six nested concrete shells with walls up to 12 inches thick cut outside noise by around 110 decibels, and the chamber floats on 68 springs on its own foundation, according to BBC Future.

What does it feel like inside?

According to BBC Future, visitors can hear people breathing across the room and stomachs gurgling; some ask to leave within seconds.

Sources

  1. Inside quietest place on Earth where you can hear your blood pumping and eyes blinking, Guinness World Records. Supports: dB_high: -20.35 dBA (2015).when an anechoic chamber at Microsoft Headquarters in Washington, USA, recorded levels of -20.35 dBAChecked 2026-11-02.
  2. Inside the quietest place on Earth, BBC Future. Supports: dB_low: -20.6 dB.in 2015 it set the official world record for silence when the background noise level inside was measured at an ear-straining -20.6 decibelsChecked 2026-11-02.
  3. Inside the quietest place on Earth, BBC Future. Supports: body: 110 dB isolation.helps to cut the noise reaching the chamber by around 110 decibelsChecked 2026-11-02.
  4. Inside the quietest place on Earth, BBC Future. Supports: body: 68 springs.The chamber itself floats on top of 68 vibration damping springs mounted on its own separate foundation slab.Checked 2026-11-02.
  5. Inside the quietest place on Earth, BBC Future. Supports: body: air-molecule noise 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.
  6. Audio Lab | Microsoft: Inside B87, Microsoft. Supports: body: Microsoft's rounded figure of -20 dB.Anechoic Chamber -20dBChecked 2026-11-02.
  7. Quietest place, Guinness World Records. Supports: body/faq: current Orfield record.In tests conducted on 19 November 2021, the ambient sound level inside the room was measured at -24.9 decibels.Checked 2026-11-02.
  8. Inside the quietest place on Earth, BBC Future. Supports: body/line: 6.36 m cube.The anechoic chamber is a cube measuring 21ft (6.36m) in each direction.Checked 2026-11-02.
  9. Inside the quietest place on Earth, BBC Future. Supports: body: six concrete layers.The chamber sits at the heart of six concrete onion layers that help to block out sounds from the outside world.Checked 2026-11-02.
  10. Inside the quietest place on Earth, BBC Future. Supports: body/faq: what visitors hear.They can hear people breathing on the other side of the room and hear stomachs gurgling.Checked 2026-11-02.
  11. Inside the quietest place on Earth, BBC Future. Supports: body: visitors' reactions.Some people want out within a few secondsChecked 2026-11-02.
  12. Audio Lab | Microsoft: Inside B87, Microsoft. Supports: body: room on springs.The entire room sits atop springs.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.