How soundproof is an office pod? dB ratings and ISO 23351-1
No office pod is completely soundproof. In ISO 23351-1 laboratory tests, enclosed pods typically reduce the level of speech escaping from them by about 15 to 30 dB. Pods rated class B or better, meaning at least 25 dB of reduction, are described as providing speech privacy in a typical office, so colleagues outside hear a murmur rather than words.
Key takeaways
- ISO 23351-1 measures how much a pod reduces the level of speech from a person inside, giving a single figure called DS,A.
- Classes run from D (15 to 20 dB) to A+ (above 33 dB); classes A+, A and B are described as giving speech privacy in a typical office.
- Field tests by Turku University of Applied Sciences found results in real rooms mostly within 1 dB of the laboratory value.
- Door seals, glass and the ventilation path decide real-world performance as much as wall panels do.
- Ask suppliers which test method sits behind any dB claim, because factory figures and ISO classes are not the same thing.
What “soundproof” means for an office pod
For an office pod, soundproof means reducing sound passing through the shell enough that speech inside cannot be understood outside, and outside chatter does not disturb the person inside. It does not mean silence, and a pod that blocked all sound would be uncomfortable and unsafe.
Two different jobs are involved. Sound insulation stops sound travelling through the walls, door and roof, and depends on mass, airtightness and construction. Sound absorption reduces echo inside the pod, which is what the felt lining does. A pod needs both: insulation for privacy, absorption so calls sound clear and the space does not feel boxy.
The decibel scale is logarithmic, so small numbers carry more weight than they appear to. According to Columbia University’s Music and Computers course text, a sound 10 dB higher sounds about twice as loud, while a 3 dB difference may seem only a tiny bit louder. A pod that reduces speech by 30 dB therefore makes it sound many times quieter, not just a little.
How ISO 23351-1 measures speech level reduction
ISO 23351-1 is the laboratory standard for rating how well pods and furniture ensembles reduce speech from a person inside them. It was published by the International Organization for Standardization in June 2020 and gives a single number, DS,A, in decibels.
The method is straightforward in principle. A loudspeaker is placed at the occupant’s position, first in an empty reverberation room and then inside the pod, and the sound power radiated into the room is measured in octave bands from 125 Hz to 8,000 Hz. The difference between the two, weighted to the spectrum of normal speech, is the speech level reduction. The Turku University of Applied Sciences acoustics laboratory, which helped develop the standard, notes that open office furniture typically achieves 0 to 5 dB DS,A, while enclosed office pods typically achieve 15 to 30 dB.
The standard has limits. It applies to complete enclosures and ensembles, not to single screens, tables or wall absorbers. Turku’s laboratory also notes that the method cannot be used for booths larger than about 10 to 15 m³, which is why a separate field method, ISO 23351-2, has been in development for larger pods and on-site testing.
The speech level reduction classes, from A+ to D
ISO 23351-1 groups results into five classes, and classes A+, A and B are the ones described as providing speech privacy in a typical office. Classes C and D can work, but only where background noise is high enough to mask what leaks out.
| Class | Speech level reduction DS,A | Speech privacy |
|---|---|---|
| A+ | Above 33 dB | Provided |
| A | 30 to 33 dB | Provided |
| B | 25 to 30 dB | Provided |
| C | 20 to 25 dB | Depends on background noise |
| D | 15 to 20 dB | Depends on background noise |
| Unclassified | Below 15 dB | Not provided |
Source for the class bands: Hushoffice, summarising ISO 23351-1:2020.
Higher is not always better. Furniture maker Haworth states that the average office has 40 to 50 dB of background noise and that classes A+, A and B all give speech privacy at that level. Hushoffice adds that the extra 3 dB of a class A pod over class B only makes a difference where background noise is below 35 dB, and that a class A pod in a very quiet office may feel too quiet to use comfortably.
What you will actually hear inside and outside a pod
Outside a class B or better pod in a normal office, you hear that someone is talking but not what they are saying. Inside, the office becomes a low background hum, and you can still hear a fire alarm.
That last point matters. A pod that cut out every sound would hide alarms and announcements. Building consultancy Sweco advises that when the fire alarm sounds, the level inside a pod should reach at least 60 dB, and that this should be measured inside pods during commissioning. Our guide to office pod fire safety in the UK covers alarms in more detail.
What you notice day to day:
- Outside the pod: speech becomes indistinct, and loud laughter or raised voices may still be faintly audible, especially in a quiet office.
- Inside the pod: keyboard noise and nearby conversations drop away, though very low-frequency sounds such as trolleys or building plant may still come through.
- On calls: the far end hears less background noise and less room echo, which often matters more to call quality than the headset.
- Fan noise: ventilation is necessary, and a well-designed fan runs quietly enough not to intrude on calls.
Do laboratory ratings hold up in real offices?
Research suggests they mostly do. In a 2023 study, Turku University of Applied Sciences measured the same booth in a laboratory and in six different rooms, and most field results were within 1 dB of the laboratory figure.
The booth scored DS,A 21.8 dB in the laboratory. Measured in the field with three different methods, it scored between 21.2 and 25.3 dB, with mean deviations from the laboratory value of 1.5 dB, -0.4 dB and 0.6 dB depending on method, as reported by Keränen, Hakala, Laukka and Hongisto at the Forum Acusticum 2023 conference. The authors also put the reproducibility of the laboratory method at a standard deviation of 1.1 dB.
The practical message is that a rating from a recognised laboratory is a reliable guide, as long as the pod on your floor is built and maintained like the one that was tested. A worn door seal, a gap at a cable entry or a damaged glass gasket will reduce performance in ways no certificate can predict.
What decides how soundproof a pod is in practice
The weakest path decides the result. Sound takes the easiest route out, so a pod with heavy walls but a leaky door or an open ventilation duct performs no better than its weakest element.
- Door and seals: the door is the largest moving part, and its perimeter seal must close evenly all round.
- Glass: laminated or thicker glazing insulates better than thin single panes.
- Ventilation path: in a separate Turku study comparing test methods, Keränen, Hakala and Hongisto note that sound leaks through ventilation ducts and door seams often fall in the 5,000 to 10,000 Hz range, which ISO 23351-1 covers.
- Floor junction: pods on uneven floors can leave gaps at the base, so levelling feet and a proper plinth seal matter.
- Room around the pod: a pod in a quiet, hard-surfaced room will sound leakier than the same pod in a busier, softer space.
Factory ratings versus ISO classes: what to ask suppliers
A factory dB figure and an ISO 23351-1 class are not interchangeable, so always ask how a number was measured. Different methods and reference sounds produce different numbers for the same pod.
The pods StillPods supplies carry factory-rated noise reduction of 30 to 45 dB depending on model; our library study pod, for example, is rated 30 to 35 dB. These are manufacturer figures, not independent ISO 23351-1 classes, and we state them that way. When comparing booths across our office phone booth range or any other supplier’s, ask:
- Which standard was used, and was it ISO 23351-1 or another method?
- Was the test done by an independent, accredited laboratory, and can you see the report?
- Was the tested unit the same model, size and glass specification as the one quoted?
- Was ventilation running during the test?
- What is the noise level of the fan at normal speed?
Our quality control process explains the checks done on pods before they leave the factory, and we can arrange a sound check on a sample unit, quoted by our team based on the model and quantity.
Frequently asked questions
Can people hear you in a soundproof office pod?
In a pod rated class B or better under ISO 23351-1, people outside in a typical office should hear that someone is speaking but not make out the words. Raised voices may still be faintly audible in a very quiet room.
What dB rating should an office phone booth have?
For confidential calls, look for at least 25 dB DS,A (class B). Class A or A+ adds a margin in quiet offices but may feel too quiet in some spaces, according to Hushoffice.
Will I hear the fire alarm inside a pod?
You should. Sweco’s guidance is that the alarm should reach at least 60 dB inside the pod, checked during commissioning. If it does not, add a sounder or visual beacon inside.
Is a meeting pod as quiet as a built room?
It can be. A pod’s performance is consistent per model, while a built room depends on its walls, ceiling void and door. We compare the two in our guide to phone booths versus meeting rooms.
Choose a pod with the right acoustic rating
Tell us what the pods are for, such as confidential HR calls, video meetings or focused study, and the background noise of your office. We will recommend models such as the S1 soundproof phone booth and share the manufacturer’s acoustic data with your quote request.
Sources
- ISO – ISO 23351-1:2020 Acoustics: measurement of speech level reduction of furniture ensembles and enclosures, Part 1 (accessed October 2026)
- Turku University of Applied Sciences – Speech level reduction of office furniture and office pods (ISO 23351-1) (accessed October 2026)
- Keränen, Hakala, Laukka and Hongisto – Alternative measurement methods for speech level reduction of booths in field conditions, Forum Acusticum 2023 (accessed October 2026)
- Keränen, Hakala and Hongisto – Comparison of ASTM E596-96 and ISO 23351-1 methods for working booths, Forum Acusticum 2023 (accessed October 2026)
- Hushoffice – Class A or class B office pods per ISO 23351-1:2020 (accessed October 2026)
- Haworth – Sound solutions for office acoustics (accessed October 2026)
- Columbia University – Music and Computers: decibels and perceived loudness (accessed October 2026)
- Sweco – Building Regulations guidance for office pods (accessed October 2026)