An experimental study of effects of concentrated compressions on sound absorption of polyester fibre panels

The effects of mechanical compressions on the acoustic properties of deformable porous materials has received a certain attention by researchers interested in the wide area of materials for acoustic purposes. Some studies have been published about the effects of uniform unidirectional static compression of layers of porous materials. Both analytic and numerical modelling were used. Reported experimental checks of predicted effects were carried out with small samples in an impedance tube. This paper presents the results of an experimental study of the effects of compressions at discrete points of panels made of polyester fibre on the sound absorption coefficient measured in a non standard reverberation room. Some decrease of the Sabine sound absorption coefficient with respect to the uncompressed panel condition was observed. The decrement magnitude is related to the surface density of compressed points.