# 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.

## 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**.

## Frequently asked questions

### What NRC should an office ceiling have?

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.

### Does high NRC make a room private?

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.

## Sources

- [ISO 354](https://www.iso.org/standards.html) — Measurement of sound absorption in a reverberation room

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Source: https://hagerstone.com/glossary/nrc-rating