Static air flow resistivity
The static air flow resistivity, term commonly reduced to
"resistivity", is one of the two most known parameters, with
the open porosity, used to describe the acoustical behavior of porous
materials.
It characterizes, partly, the
visco-inertial effects at low frequencies (when the viscous boundary layer
is of the order of magnitude of the the characteritic size of the pores).
The models by Delany-Bazley [DB70] and Delany-Bazley-Miki
[Mik90] use only this parameter to described the
behavior of fibrous acoustical materials.
The static air flow resistivity is usually identified by the greek letter
, its dimension in the international system is
N.s.m-4 or Pa.s.m-2.
|
(1) |
with
|
(2) |
where
is the open porosity of the material,
the dynamic viscosity of air
(
1.84
10-5 N.s.m-2 at ambiant temperature and pressure conditions) and
is the
static permeability of the material.
Range of values
For acoustical materials, its range of values is approximately [103 106].
The resistivity can be directly measured. [ISO 9053]
References
[ISO 9053] European Committee for Standardization, Acoustics - Materials for acoustical applications - Determination of airflow resistance
[DB70] Delany M. E. and Bazley E. N.,
Acoustical properties of fibrous absorbent materials, Applied
Acoustics 3, 1970, pp. 105-116
[Mik90] Miki Y.,
Acoustical properties of porous materials - Modifications of
Delany-Bazley models, J. Acoust. Soc. Jpn (E). 11(1), 1990, pp. 19-24
- Contents
- Definition
- Range of values
- See also
- "Resistivity" measurement
- Comment
- by sending an e-mail to apmr@matelys.com with the current page title.
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