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FocusPod Max™NRC Rating
Definition
NRC Rating
What the noise reduction coefficient actually measures, and the thing it is most often confused with.
NRC stands for Noise Reduction Coefficient. It is a single number between 0 and 1 describing how much sound a material absorbs rather than reflects. An NRC of 0.0 reflects all sound; 1.0 absorbs all of it. It is measured under ASTM C423 by averaging absorption at 250, 500, 1000 and 2000 Hz. Crucially, NRC describes absorption inside a space — it says nothing about how much sound passes through a wall.
How NRC is measured
ASTM C423A sample of the material is placed in a reverberation chamber and absorption is measured across four frequency bands — 250, 500, 1000 and 2000 Hz. Those four figures are averaged and rounded to the nearest 0.05, giving the single NRC value.
Because it is an average of four mid-range frequencies, NRC deliberately ignores low frequencies. A material with an NRC of 0.85 may perform very differently against a bass-heavy noise source than against speech, and the single number will not tell you.
What the numbers mean
In practice0.00 to 0.20 — hard, reflective surfaces. Glass, concrete, painted plasterboard, most flooring.
0.30 to 0.60 — moderately absorptive. Carpet, heavy curtains, upholstered furniture.
0.70 to 0.90 — purpose-made acoustic material. Mineral wool panels, thick acoustic felt, most acoustic ceiling tiles.
0.90 and above — high-performance absorption, usually thick porous material or specialist treatments. Values above 1.0 appear occasionally and are an artefact of the test method rather than material absorbing more sound than exists.
The confusion worth avoiding
Absorption is not isolationNRC measures absorption. It does not measure sound transmission. This is the single most common misunderstanding in workplace acoustics and it costs organisations real money.
Putting high-NRC panels on a wall reduces reflections and reverberation inside the room. It makes the room sound less harsh and speech within it more intelligible. It does almost nothing to stop a conversation being heard on the other side of that wall.
Containing sound requires mass and an unbroken seal, which is what STC and speech level reduction measure. If the problem is people overhearing each other, absorption is the wrong tool and acoustic panels are money spent on the wrong thing.
Where NRC does matter
Inside an enclosed spaceWithin an acoustic booth or a small meeting room, absorption matters a great deal. A sealed box with hard internal surfaces is acoustically unpleasant — speech reflects, the space sounds boxy, and microphones pick up the room rather than the voice.
That is why booth interiors use acoustic felt and carpet rather than hard finishes. The absorption is not there to stop sound escaping. It is there to make the inside comfortable to speak in and to keep video calls sounding clean.
Common questions
What does NRC rating mean?
NRC stands for Noise Reduction Coefficient. It is a number between 0 and 1 describing how much sound a material absorbs rather than reflects, measured under ASTM C423 by averaging absorption at 250, 500, 1000 and 2000 Hz. An NRC of 0.8 means roughly 80 percent of mid-frequency sound striking the material is absorbed.
What is a good NRC rating?
It depends what the material is for. Purpose-made acoustic panels typically sit between 0.70 and 0.90. Carpet and heavy curtains land around 0.30 to 0.60. Hard surfaces such as glass and concrete are 0.20 or below. For treating reverberation inside a room, 0.70 and above is generally considered effective.
Is NRC the same as soundproofing?
No, and this is the most common misunderstanding in workplace acoustics. NRC measures absorption within a space. Soundproofing means stopping sound passing between spaces, which is measured by STC or by speech level reduction under ISO 23351. High-NRC panels on a wall will not stop a conversation being overheard on the other side.
Can NRC be higher than 1.0?
Occasionally values above 1.0 are published. This is an artefact of the test method — edge effects in the reverberation chamber can produce apparent absorption above 100 percent — rather than a material absorbing more sound than reaches it.
Does NRC matter for office pods?
Inside them, yes. Booth interiors use acoustic felt and carpet so the enclosed space does not sound harsh and so microphones pick up the speaker rather than the room. It is not what stops sound escaping the pod — that is the panel construction and door seal.
Related: STC rating · reverberation time · sound masking · full glossary
Specifying an acoustic booth?
We publish airflow, speech level reduction and weight figures for every model, and we will send the test report references if you ask.