"Acoustical" parameters
A small part of the "Acoustical" parameters used to describe
the visco-inertial and thermal behvior of acoustical porous materials
are directly measurable. This is the case for the
open porosity, the
static air flow resistivity and the
high frequency limit of the dynamic tortuosity.
The devices used in these cases are borrowed from other porous
materials (such as rocks) or are adapted from these porous materials
to acoustical ones (which have usually very large permeability and
porosity compared to rocks).
The major part of the "Acoustical" parameters are estimated.
Their characterization required to use a specific
propagation model assuming a motionless skeleton
can be from standing waves tubes measurements
via analytical expressions [OPTV02,PO06] indirect measurements, or curve fiting techniques
based on a propagation model assuming a motionless skeleton
"Elastical" parameters
Most of the experimental methods used to characterize "elastical" parameters (Young's moduli, loss factors and Poisson's ratio) are adaptations of techniques used for polymers or metal [Ashby.Book,Corsaro.Book,Hilyard.Book]. Modifications of existing devices are usually due to account for the interaction between the two phases of an acoustical porous materials or to account for specific ranges of values for acoustical porous materials. Young's moduli and loss factors of such materials range from approximately 100 to 107 N.m-2 and from 10-2 to 1 respectively.
References
[OPT02]
X. Olny, R. Panneton and J. Tran-Van, An indirect acoustical method for determining intrinsic parameters of porous materials
in Poromechanics II, proceedings of the 2nd Biot conference, Grenoble (France), 2002.
[P006]
R. Panneton and X. Olny,
Acoustical determination of the parameters governing viscous dissipation in porous media, J. Acoust. Soc. Am. 119(4), 2006, pp. 2027-2040,
.
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