NOISE ABSORPTION COEFFICIENTS ACCORDING TO ASTM C423 STANDARD ASTM is the American Society for Testing and Materials, its technical standards are used mainly in the USA but also enjoy great international prestige.
ASTM C423 is a standard test method for classifying the sound absorption of a material and its coefficients are measured by means of a reverberation room.
Noise reduction coefficient NRC It ranges from 0.00 to 1.00 and describes the average acoustic absorption of a material.
NRC 0.00 indicates that the object has no sound absorption, e.g. a very thick concrete wall has approximately that rating.
On the contrary, NRC 1.00 indicates the maximum sound absorption.
Sound Absorption Average SAA It is a coefficient that ASTM derived from NRC and that uses a wider range of measurement.
It is more reliable than the NRC about the absorption of low frequencies.