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FocusPod Max™Workplace Acoustics Glossary
Glossary
Workplace acoustics, in plain English.
The terms that come up when specifying a booth or treating a floor, explained without the sales copy.
Workplace acoustics uses four measurements that are routinely confused. NRC measures absorption within a space. STC measures sound blocked by a wall or door. RT60 measures how long sound takes to fade. ISO 23351-1 speech level reduction measures a complete enclosure such as an office booth, and is the only one of the four that describes a pod. Absorption and isolation are different problems with different solutions.
The one distinction that matters most
Absorption is not isolationAlmost every expensive mistake in workplace acoustics comes from confusing two things: reducing sound within a space, and stopping sound leaving it.
Absorption — measured by NRC — soaks up reflections. It makes a room sound less harsh and reduces reverberation. Acoustic panels, carpet and ceiling treatment all do this.
Isolation — measured by STC for a single element, or by speech level reduction under ISO 23351 for a complete enclosure — stops sound passing between spaces. It requires mass and an unbroken seal.
Putting acoustic panels on a wall to stop people being overheard does not work, and it is done constantly. If the problem is privacy, absorption is the wrong tool.
The terms
NRC rating
Noise reduction coefficient. How much sound a material absorbs rather than reflects, from 0 to 1.
IsolationSTC rating
Sound transmission class. How well a wall, floor or door blocks sound passing through it.
DecayReverberation time
RT60. How long sound takes to fade in a space, and why long decay makes offices tiring.
DistractionSound masking
Adding engineered background sound so distant speech becomes unintelligible.
EnclosureISO 23351-1
Speech level reduction for complete booths, sorted into classes. Class A is the highest.
ProductOffice pod
Freestanding soundproof enclosure inside an existing floor. What they are and how they work.
Which measurement applies to what
Quick reference| If you want to | The measurement is | The solution is |
|---|---|---|
| Stop a room echoing | NRC, RT60 | Absorption — panels, ceiling treatment, soft finishes |
| Stop noise through a wall | STC | Mass and sealing — heavier construction, better seals |
| Contain a phone call | ISO 23351-1, Class A | An enclosure — an acoustic booth |
| Reduce ambient distraction | dBA at the desk | Masking, plus absorption |
| Have a confidential conversation | ISO 23351-1, Class A | An enclosure. Nothing else achieves it |
Common questions
What is the difference between NRC and STC?
NRC measures how much sound a material absorbs within a space. STC measures how much sound a wall, floor or door blocks from passing through it. They are unrelated: acoustic foam has a high NRC and almost no STC, meaning it reduces echo but blocks nothing.
What acoustic rating do office pods use?
Speech level reduction under ISO 23351-1, expressed in decibels and sorted into classes. Class A is the highest band and corresponds to roughly 30 dB. Booths use this rather than STC because STC tests a single element while a booth is a complete enclosure limited by its door seal.
What does Class A mean for an acoustic booth?
Class A is the highest band under ISO 23351-1 for speech level reduction, around 30 dB. In practice it means a normal speaking voice inside the booth is not intelligible outside it — someone a metre away hears that a conversation is happening but cannot make out the words.
Does absorption make a room private?
No. Absorption reduces reverberation and makes a space more comfortable, but it does not stop conversations being overheard. Privacy requires enclosure — mass and an unbroken seal. This is the most common and most expensive misunderstanding in workplace acoustics.
What is a good reverberation time for an office?
Between 0.4 and 0.6 seconds. Untreated offices typically sit around 0.6 to 0.8, and hard-surfaced spaces with concrete and glass often exceed 1.0 second, at which point speech intelligibility drops and people start raising their voices.
If you are specifying a booth, the buyers guide covers what to ask suppliers about acoustic claims. The range and prices are published in full.
Comparing acoustic claims?
Send us any supplier's specification, including ours, and we will tell you what it actually says and what it leaves out.