Archives of Acoustics, 36, 3, pp. 561–574, 2011

An Inverse Method to Obtain Porosity, Fibre Diameter and Density of Fibrous Sound Absorbing Materials

Jesus ALBA
Polytechnic University of Valencia Research Institute for Integrated Coastal Zone Management-IGIC

Romina del REY
Polytechnic University of Valencia Research Institute for Integrated Coastal Zone Management-IGIC

Jaime RAMIS
University of Alicante Department of Physics, System Engineering and Signal Theory

Jorge P. ARENAS
University Austral de Chile Institute of Acoustics

Characterization of sound absorbing materials is essential to predict its acoustic
behaviour. The most commonly used models to do so consider the flow resistiv-
ity, porosity, and average fibre diameter as parameters to determine the acoustic
impedance and sound absorbing coefficient. Besides direct experimental techniques,
numerical approaches appear to be an alternative to estimate the material’s pa-
rameters. In this work an inverse numerical method to obtain some parameters of
a fibrous material is presented. Using measurements of the normal incidence sound
absorption coefficient and then using the model proposed by Voronina, subsequent
application of basic minimization techniques allows one to obtain the porosity, aver-
age fibre diameter and density of a sound absorbing material. The numerical results
agree fairly well with the experimental data.
Keywords: sound absorption; fibrous materials; porous material; material character- ization
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