Effects of compression on the sound absorption of fibrous materials

During the compression of a fibrous mat, it is well known that the absorpti on properties are decreasing. In order to predict this change, some heurist ic formulae are proposed which take into account the modifications of the p hysical parameters (porosity, resistivity, tortuosity and shape factors) wh ich enter the standard "equivalent fluid" model. Numerical predictions are then discussed and compared to experimental data obtained on a fibrous mate rial (uncompressed and then compressed) used in the automotive industry. (C ) 2000 Elsevier Science Ltd. All rights reserved.