Acoustic measurement of the flow resistivity of a rigid porous material via low frequency transmitted waves—Frequency approach

Abstract

In this work, an acoustic characterization process is proposed to measure the flow resistivity of porous materials with rigid frame via transmitted waves at very low frequency. The equivalent fluid theory is considered. Two expressions of the transmission coefficient have been established in the Darcy regime. The first depends on the frequency, porosity and air flow resistivity, while the second is frequency independent and depends only on the air flow resistivity. The inverse problem is solved in the frequency domain. The inverted values of the air flow resistivity are determined using the two low-frequency expressions of the transmission coefficients. The tests are carried out using two industrial plastic foam samples frequently used in thermal and sound insulation. The reliability of the results obtained is discussed and compared with those given by conventional methods.