Evaluation of Two Alternative Procedures for Measuring Airflow Resistance of Sound Absorbing Materials

It is well known that sound absorption and sound transmission properties of open porous materials
are highly dependent on their airflow resistance values. Low values of airflow resistance indicate little
resistance for air streaming through the porous material and high values are a sign that most of the pores
inside the material are closed. The laboratory procedures for measuring airflow resistance have been stan-
dardized by several organizations, including ISO and ASTM for both alternate flow and continuous flow.
However, practical implementation of these standardized methods could be both complex and expensive.
In this work, two indirect alternative measurement procedures were compared against the alternate flow
standardized technique. The techniques were tested using three families of eco-friendly sound absorbent
materials: recycled polyurethane foams, coconut natural fibres, and recycled polyester fibres. It is found
that the values of airflow resistance measured using both alternative methods are very similar. There is
also a good correlation between the values obtained through alternative and standardized methods.