Introduction
If you are selecting acoustic panels for an office, studio, school, or commercial space, you have probably encountered the term NRC rating. But what does it actually mean? How is it measured? What NRC rating do you need for your project?
In this guide, Linyi Solland International Trade Co., Ltd. explains NRC ratings in plain language so you can specify the right acoustic panel with confidence.
What Is NRC Rating?
NRC (Noise Reduction Coefficient) is a single-number rating that represents the average sound absorption of a material across the mid-frequency range (250 Hz, 500 Hz, 1000 Hz, 2000 Hz).
The Formula
NRC = (α₂₅₀ + α₅₀₀ + α₁₀₀₀ + α₂₀₀₀) / 4 Where α = sound absorption coefficient at each frequency
The result is a number between 0 and 1:
- NRC = 0.00: Perfect reflector (no absorption, all sound bounces)
- NRC = 1.00: Perfect absorber (no reflection, all sound absorbed)
- NRC = 0.50: Half the sound is absorbed, half is reflected
Visual Interpretation
| NRC Rating | % of Sound Absorbed | Real-World Analogy |
|---|---|---|
| 0.00 | 0% | Bare concrete wall |
| 0.05 | 5% | Painted drywall |
| 0.10 | 10% | Unpainted wood |
| 0.20 | 20% | Carpet on concrete |
| 0.30 | 30% | Standard drywall |
| 0.50 | 50% | Acoustic ceiling tile |
| 0.70 | 70% | Quality acoustic panel |
| 0.85 | 85% | Premium acoustic panel |
| 0.95 | 95% | Professional studio foam |
| 1.00 | 100% | Anechoic chamber (rare) |
How Is NRC Measured?
Test Standard: ASTM C423
The ASTM C423 standard is the most widely used method for measuring sound absorption.
Test setup:
- Two reverberation rooms — one with the material, one without
- Sound source generates broadband noise
- Microphones measure decay time in both rooms
- Absorption coefficient (α) is calculated at each frequency
- NRC is the average of four octaves (250, 500, 1000, 2000 Hz)
Other Test Standards
| Standard | Region | Notes |
|---|---|---|
| ASTM C423 | North America | Most common |
| ISO 354 | International | Equivalent to ASTM C423 |
| EN ISO 11654 | Europe | Single-number rating (αw) |
| GB/T 20247 | China | Chinese equivalent |
Frequency Matters
NRC is an average of mid-frequencies. For some applications, you need to look at the full frequency spectrum:
- Speech clarity (offices, classrooms): Focus on 500–2000 Hz
- Music recording: Focus on 100–4000 Hz
- Low-frequency absorption (home theater, bass traps): 63–250 Hz
Solland provides full frequency data for our acoustic panels on request.
NRC by Acoustic Panel Type
Different acoustic panels have different NRC ratings:
| Panel Type | Typical NRC | Best For |
|---|---|---|
| Bare drywall | 0.05–0.10 | Reference only |
| Standard drywall | 0.10–0.20 | Low-impact areas |
| Foam panel (standard) | 0.30–0.50 | Home studios |
| Fabric-wrapped panel | 0.50–0.70 | Offices, schools |
| PET felt panel | 0.55–0.75 | Modern offices |
| Wood slat acoustic panel | 0.65–0.85 | Premium offices |
| Perforated wood panel | 0.70–0.85 | Auditoriums |
| High-density fibreglass panel | 0.85–0.95 | Recording studios |
| Mineral wool panel | 0.85–1.00 | Professional studios |
Solland Acoustic Panel NRC Ratings
| Product | NRC Rating | Frequency Range |
|---|---|---|
| Wood Slat Acoustic Panel (Standard) | 0.70 | 250–2000 Hz |
| Wood Slat Acoustic Panel (Premium) | 0.85 | 200–4000 Hz |
| Wood Slat Acoustic Panel (Studio) | 0.95 | 100–5000 Hz |
| PET Felt Acoustic Panel | 0.75 | 250–2000 Hz |
| Fabric-Wrapped Acoustic Panel | 0.70 | 250–2000 Hz |
| Perforated Wood Acoustic Panel | 0.80 | 250–2000 Hz |
| Mineral Wool Acoustic Panel | 0.90 | 100–4000 Hz |
| MWool (Fiberglass) Panel | 0.95 | 100–5000 Hz |
All ratings tested per ASTM C423 at SGS-certified lab in China.
What NRC Rating Do You Need?
The right NRC rating depends on space type, room size, and use case:
NRC 0.20–0.40 (Light Absorption)
Use for:
