What is the Static Airflow Resistivity?
The static airflow resistivity (SAR), often represented by the Greek letter σ (sigma), is a very important parameter for acoustic material modeling. In fact, one of the first acoustic models presented by Delany & Bazley in 1970  was only relying on this parameter.
SAR is not only useful for acoustic simulations, it is also an excellent quality control tool, in fact, a lack of consistency in a given fibrous or porous material can also indicate manufacturing malfunction or material variability. The measurement of the airflow resistivity is a very good tool for quality control of porous materials during manufacturing process or at reception of suppliers materials.
How to Measure the Static Airflow Resistivity?
Equipment: Static Airflow Resistivity Meter
Standards: ASTM C 522-03, ISO 9053-2:2020
Method: Electronic system for the measurement of flow resistance 
- σ – Static airflow resistivity (Rayl/m or Pa.s/m²)
- k – Static permeability (m²)
- L – Sample thickness (m)
 REF Delany, M. E. et Bazley, E. N. (1970). Acoustical properties of fibrous absorbent materials. Applied Acoustics, volume 3, numéro 2, p. 105-16
 M.R. Stinson and G.A. Daigle, « Electronic system for the measurement of flow resistance » J. Acoust. Soc. Am. 83, 2422-2422 (1988)