When designing room acoustics, there are many different ratings that may be applied to a product to identify how it will shape the sound of a space or between spaces. You may come across ratings for NRC (Noise Reduction Coefficient), SAA (Sound Absorption Average), STC (Sound Transmission Class), IIC (Impact Insulation Class) or CAC (Ceiling Attenuation Class).

Similar to the NRC Rating and determined using the same ASTM, an SAA Rating is an average measurement for a building material’s sound absorption performance. Adopted into the ASTM-C423 in 1999, the SAA rating was developed to give a more accurate average of how materials absorbed sound across many frequencies. Where NRC ratings consider sound absorption at four frequencies, SAA Ratings are an calculated using twelve one-third octave bands ranging between 200 and 2,500 Hz.

These ratings are classified on a scale from 0 to 1, with 0 indicating no absorption and 1 indicating complete absorption.  SAA Ratings are rounded to the nearest 0.01, whereas NRC Ratings are rounded to the nearest 0.05.

An SAA offers a more accurate idea for low frequency sound absorption performance. This is key when considering the low frequency output from mechanical and HVAC systems. When selecting acoustical material it is key to understand not only the varied uses of a space, but also the building components that might be out-of-sight.

As you vet an acoustical material, be sure to request a manufacturer’s independent test data for the ASTM-C423 standard. BASWA Systems are all tested using this ASTM, and include both A & E mountings to ensure our understanding of how each system would perform in the installed conditions of your project, whether there is a plenum above the system or not. BASWA proudly offers products that acoustically perform in a consistent manner, regardless of any differing conditions.