Sound Absorption of Multilayered Samples Composed by Different Porous Materials and Perforated Facing

Abstract

This paper reports the results of normal incidence sound absorption measurements done over three different acoustic materials with varying thickness. A microperforated panel (MPP) was added to cover the absorber, in some cases leaving an air cavity between them. The measurements were done in an impedance tube, according to ISO 10534-2:1998. The aim was to find the best setup of the test samples to build a device that improves the absorption especially at low frequency. It is concluded that having the acoustic materials in contact with the MPP and backed by an air layer gives the expected results.