NRC Rating: How Much Sound a Surface Absorbs
NRC — Noise Reduction Coefficient — is a single number between 0 and 1 describing how much sound a surface absorbs rather than reflects. An NRC of 0.70 means the material absorbs roughly 70% of the sound striking it, averaged across the speech-frequency range.
By Dhruv Agarwal · · 1 min read
Why it matters
Open-plan offices fail most often on noise, and the fix is largely absorption: ceilings, carpet and wall panels that stop voices reflecting across the floor. NRC is the number that tells you how much a material will help.
How it works in practice
| NRC | Behaviour | Example |
|---|---|---|
| 0.0 – 0.2 | Reflective | Plasterboard, glass, stone |
| 0.4 – 0.6 | Moderate absorption | Standard ceiling tiles |
| 0.7 – 0.9 | High absorption | Acoustic tiles, baffles, fabric panels |
Common mistakes
- Confusing absorption with insulation. High NRC does not stop sound passing through a wall.
- Hard finishes everywhere. Glass, stone and plasterboard together make a loud office.
- Ignoring the ceiling. It is usually the most effective place to absorb.
Standards referenced
Sound absorption is measured in a reverberation room under ISO 354.
Standards referenced
- ISO 354 — Measurement of sound absorption in a reverberation room (ISO)
Frequently asked
Open-plan offices benefit from ceilings around NRC 0.70 or above, because the ceiling is the largest continuous surface and controls how much speech bounces around the floor. Lower-NRC ceilings make open plans noticeably louder.
No. NRC measures absorption inside a room, not blocking between rooms. Privacy between rooms depends on sound insulation — walls to slab, sealed plenums and good glazing — which is a different property entirely.
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