PU PROBE BASED IN SITU IMPEDANCE MEASUREMENTS OF A SLOTTED PANEL ABSORBER

In this paper the results of in situ acoustic surface impedance measurements on a slotted /perforated absorber are presented. For this purpose, a PU match probe was used measuring both sound pressure and particle velocity. This novel free field method allows measurements on a large variety of materials and geometries, e.g. flat and curved as installed. The benefit of its high spatial resolution was used to scan the slotted absorber. Measurements were taken each 5mm, allowing to calculate the spatial averaged impedance, the reflection- and absorption coefficients. Color maps of the absorption across the scanned area were also plotted for several frequencies. Finally, an even smaller PU probe was built and used to measure variations of the acoustic impedance inside one of the slots of the absorber.