Every professional acoustic panel quotation includes absorption data — and every year, buyers make decisions based on numbers they have not been taught to read. NRC, SAA, octave-band coefficients: the vocabulary is technical, but the logic is simple. This guide gives you the working knowledge to compare panels and catch the tricks that mislead less careful buyers.
What the numbers measure
An absorption coefficient expresses how much sound energy a material absorbs at a given frequency, on a scale from 0 (fully reflective) to 1.00 (fully absorptive). These coefficients are measured in a reverberation room — the ISO 354 standard used in Europe and Asia — or in an impedance tube and reverberation room under ASTM C423 in North America.
NRC: the classic single number
The Noise Reduction Coefficient (NRC) averages a panel’s absorption at four frequencies: 250, 500, 1000 and 2000 Hz. It compresses performance into one figure — NRC 0.85 on a 12mm PET panel, for example. Its strength is simplicity; its weakness is that it ignores both very low (125 Hz) and high (4000 Hz) frequencies where real rooms have problems.
SAA: the more modern average
The Sound Absorption Average (SAA), defined by ASTM C423, averages twelve one-third-octave bands from 200 Hz to 2500 Hz. It gives a fairer picture of mid-and-high frequency performance, and typically reads a few points higher than NRC on the same panel — an SAA of 0.90 does not mean a panel “beats” an NRC of 0.85; they are different scales.
How to read the full report like a pro
- Look at the octave bands, not just the average. Two panels with identical NRC can behave differently at 250 Hz — the frequency of speech energy and the hardest problem in offices. For meeting rooms, check the 250–500 Hz row specifically.
- Check the mounting. Test reports state the mounting condition: directly on surface (Type A/E-100) or with an air gap (Type D-50/E-200 and so on). A panel tested with a 50mm cavity can lose several points of low-frequency absorption when glued flat to a wall.
- Check the thickness and the tested construction. Absorption data belongs to a specific thickness and density. A report for 24mm does not describe 9mm.
- Beware of “absorption class” shorthand. Europe uses Class A–E per ISO 11654, where Class A means a weighted absorption coefficient αw ≥ 0.90. It is legitimate — but it is calculated differently from NRC, so do not mix the scales.
Practical comparison advice
When comparing suppliers, request the full test report (not a datasheet summary), confirm the mounting condition matches your installation, and compare per-frequency data for the room type you serve. A supplier confident in its product hands over laboratory reports without hesitation.
MST Acoustics data practice
All MST Acoustics PET panels, baffles and wood slat panels are tested under ISO 354 with per-octave-band data published for each thickness, and full reports are available to customers and their acoustic consultants on request. Our technical team can also run a reverberation estimate for your project dimensions — send us the room, and we will show what the numbers mean in practice.
