Absorption acoustique - ASTM C423


Reverberation room according to ISO 354Type G mountingIt's mainly used for testing fabric curtains.The test specimen is hung parallel to the room surface.The numeric suffix (e.g. Type G-100) is the distance in mm from the test specimen to the room surface.The test specimen can be:- flat- with fullness (with different percentages)C. Room surfaceT. Test specimenG. Mounting Type G - With fullnessA. Airspace behind the specimenS. Dodecahedral sound sourceD. DiffuserM. Microphone
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.