Guide · · 5 min read
How soundproof is an office pod? dB, NRC and ISO 23351-1 explained
What dB figures, NRC ratings and ISO 23351-1 classes tell you about an office pod's acoustics — and the questions to ask any supplier before you buy.
No office pod is completely silent — and it shouldn't be, because you still need to hear the fire alarm. A good pod keeps a conversation private from the people outside and cuts open-plan noise enough for a clear call. The trouble is that suppliers describe acoustics with different numbers that measure different things.
Two numbers that measure different things
Decibels (dB): how much the pod keeps speech in
A dB figure for a pod — usually called sound insulation or speech level reduction — describes privacy: how much quieter a voice is outside the pod than inside.
The laboratory test for this is ISO 23351-1. It measures the speech level with and without the pod in place and compares the two; the difference, in dB, is the speech level reduction.
NRC: how much sound the panels absorb
The noise reduction coefficient (NRC) is a single number from 0 to 1, averaged across frequencies from 250 to 2,000 Hz, that says how much sound a material absorbs instead of reflecting. Panels rated NRC 0.95 absorb most of the sound that hits them, which cuts echo inside the pod and makes your voice clearer on a call.
What NRC doesn't tell you is how much sound gets through the walls. A pod lined with NRC 0.95 panels is not “95% soundproof” — that would be a different measurement altogether.
ISO 23351-1 classes
| Class | Speech level reduction |
|---|---|
| A+ | More than 33 dB |
| A | 30–33 dB |
| B | 25–30 dB |
| C | 20–25 dB |
| D | 15–20 dB |
Class B or better — a speech level reduction of at least 25 dB — is the level commonly cited for good speech privacy in a typical office. Below that, privacy depends on how noisy the room around the pod is.
What suppliers publish
Figures on UK suppliers' websites in September 2026 were mostly between 25 and 35 dB. Some state the ISO 23351-1 class their pods achieved; others give a dB number without saying how it was measured. The two aren't directly comparable, so it's worth asking.
Our figures
- Solo Phone Booth: rated at 38–40 dB of sound insulation. This is the manufacturer's stated figure, not an ISO 23351-1 class, so don't compare it directly with a class rating.
- Phone booth, Focus Work Capsule, Meeting Pod 1–4 and Meeting Pod 1–7: all lined with acoustic panels rated NRC 0.95.
- The phone booth door is double-glazed tempered safety glass.
See our office phone booths, meeting pods or all office pods.
Questions to ask any supplier
- Is your dB figure a speech level reduction measured to ISO 23351-1? If not, how was it measured?
- Which class did the pod achieve, and can I see the test report?
- What NRC are the interior panels?
- How is air moved in and out, and how loud is the fan?
- Will our fire alarm be heard inside? Sweco's guidance is at least 60 dB inside the pod.
Looking for a booth to record in rather than to take calls? Read soundproof booth: office pod or vocal booth?
