An SAA (Sound Absorption Average) rating is a single number that describes how much sound a material absorbs across the core range of human speech. Like the NRC (Noise Reduction Coefficient), it is a single-number rating averaged from laboratory absorption coefficients, and a higher number means more absorption. The difference is resolution: where NRC averages four frequencies, SAA averages twelve, giving a more precise picture of how a material will perform in a real room. When designing room acoustics, you will likely encounter SAA alongside NRC for in-room absorption, STC (Sound Transmission Class) and CAC (Ceiling Attenuation Class) for sound traveling between rooms, and IIC (Impact Insulation Class) for impact noise between floors.

SAA is defined in ASTM C423, the Standard Test Method for Sound Absorption and Sound Absorption Coefficients by the Reverberation Room Method, and comes from the same laboratory test as NRC: sound decay is measured in a reverberation room with and without a sample of the material installed. SAA is calculated as the average of the absorption coefficients for the twelve one-third octave bands from 200 Hz to 2,500 Hz and is rounded to the nearest 0.01, compared with NRC's rounding to the nearest 0.05. That finer rounding and wider sample of frequencies make SAA better at distinguishing two products that share the same NRC.

Neither SAA nor NRC fully captures low-frequency performance. SAA's range begins at 200 Hz, so it does not include the 125 Hz band, where much of the rumble from mechanical and HVAC systems sits. In spaces near mechanical rooms, or anywhere low-frequency sound is a concern, review the full frequency-by-frequency absorption data from ASTM C423 testing rather than relying on a single-number rating. When selecting an acoustical material, it is important to understand not only the varied uses of a space but also the building systems that may be out of sight.

As you vet an acoustical material, request the manufacturer's independent test data under ASTM C423 and check the mounting condition used, since a sample tested with an airspace behind it can report different absorption than the same sample mounted directly against a surface. Each BASWA test data sheet reports ASTM C423 results and states the mounting used, so you can compare performance to your project's actual conditions. Review BASWA's full test documentation on our Technical Data page.