When you compare acoustic ceilings you’ll see two key numbers: αw and NRC. Both describe how much sound a tile absorbs, on a scale from 0 (fully reflective) to 1 (fully absorptive). The higher the number, the quieter and more comfortable the room.
αw (weighted sound absorption coefficient)
αw is a single European figure (EN ISO 11654) derived from absorption across frequencies, rounded into a curve. It also maps to absorption Classes A–E, where Class A is αw ≥ 0.90 (the best) down to Class E.
NRC (noise reduction coefficient)
NRC is the North American average of absorption at 250, 500, 1000 and 2000 Hz. An NRC of 0.90 means roughly 90% of mid-frequency sound is absorbed.
Which to specify
- Open-plan offices, restaurants, call centres: αw 0.90–1.0 / Class A
- General offices, classrooms: αw 0.60–0.85
- Corridors, retail, back-of-house: αw 0.50–0.70
- Feature/reflective designs: lower αw is fine where acoustics are secondary
OWA publishes αw and NRC for every design (for example, fleece-laminated tiles reaching αw 1.0), so you can match the rating to the room with confidence.
Frequently Asked Questions
What is a good NRC for a ceiling?
An NRC of 0.70+ is good for general spaces; 0.85–1.0 is ideal for noisy, open-plan or speech-critical rooms.
What does αw mean on a ceiling tile?
αw is the weighted sound absorption coefficient (0–1) under EN ISO 11654. Higher means more absorption; αw ≥ 0.90 is Class A, the highest performance class.
Is αw the same as NRC?
They measure the same thing — sound absorption — but with different methods. αw is the European weighted value; NRC is the North American average. Both run 0 to 1.
