ASTM C522-03(2009)e1
(Test Method)Standard Test Method for Airflow Resistance of Acoustical Materials
Standard Test Method for Airflow Resistance of Acoustical Materials
SIGNIFICANCE AND USE
The specific airflow resistance of an acoustical material is one of the properties that determine its sound-absorptive and sound-transmitting properties. Measurement of specific airflow resistance is useful during product development, for quality control during manufacture, and for specification purposes.
Valid measurements are made only in the region of laminar airflow where, aside from random measurement errors, the airflow resistance (R = P/U) is constant. When the airflow is turbulent, the apparent airflow resistance increases with an increase of volume velocity and the term “airflow resistance” does not apply.
The specific airflow resistance measured by this test method may differ from the specific resistance measured by the impedance tube method in Test Method E384 for two reasons. In the presence of sound, the particle velocity inside a porous material is alternating while in this test method, the velocity is constant and in one direction only. Also, the particle velocity inside a porous material is not the same as the linear velocity measured outside the specimen.
SCOPE
1.1 This test method covers the measurement of airflow resistance and the related measurements of specific airflow resistance and airflow resistivity of porous materials that can be used for the absorption and attenuation of sound. Materials cover a range from thick boards or blankets to thin mats, fabrics, papers, and screens. When the material is anisotropic, provision is made for measurements along different axes of the specimen.
1.2 This test method is designed for the measurement of values of specific airflow resistance ranging from 100 to 10 000 mks rayls (Pa·s/m) with linear airflow velocities ranging from 0.5 to 50 mm/s and pressure differences across the specimen ranging from 0.1 to 250 Pa. The upper limit of this range of linear airflow velocities is a point at which the airflow through most porous materials is in partial or complete transition from laminar to turbulent flow.
1.3 A procedure for accrediting a laboratory for the purposes of this test method is given in Annex A1.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4.1 Table 1 is provided for user to convert into cgs units.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
General Information
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
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Designation:C522 −03(Reapproved 2009)
Standard Test Method for
Airflow Resistance of Acoustical Materials
This standard is issued under the fixed designation C522; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
ε NOTE—Section 1.4.1 was editorially added in March 2010.
1. Scope E384 Test Method for Knoop and Vickers Hardness of
Materials
1.1 This test method covers the measurement of airflow
C634 Terminology Relating to Building and Environmental
resistance and the related measurements of specific airflow
Acoustics
resistanceandairflowresistivityofporousmaterialsthatcanbe
E691 Practice for Conducting an Interlaboratory Study to
used for the absorption and attenuation of sound. Materials
Determine the Precision of a Test Method
cover a range from thick boards or blankets to thin mats,
fabrics, papers, and screens. When the material is anisotropic,
3. Terminology
provision is made for measurements along different axes of the
3.1 Definitions: The definitions used in this test method are
specimen.
contained in Terminology C634.
1.2 This test method is designed for the measurement of
3.2 Definitions of Terms Specific to This Standard: The
values of specific airflow resistance ranging from 100 to
following items have been modified to exclude alternating
10 000 mks rayls (Pa·s/m) with linear airflow velocities rang-
flow.
ing from 0.5 to 50 mm/s and pressure differences across the
3.2.1 airflow resistance, R; mks acoustic ohm
specimen ranging from 0.1 to 250 Pa. The upper limit of this
(Pa·s/m )—the quotient of the air pressure difference across a
range of linear airflow velocities is a point at which the airflow
specimendividedbythevolumevelocityofairflowthroughthe
through most porous materials is in partial or complete
specimen.
transition from laminar to turbulent flow.
3.2.2 airflow resistivity, r ; mks rayl/m (Pa·s/m )—ofa
1.3 A procedure for accrediting a laboratory for the pur-
homogeneous material, the quotient of its specific airflow
poses of this test method is given in Annex A1.
resistance divided by its thickness.
1.4 The values stated in SI units are to be regarded as
3.2.3 lateral airflow resistivity— of an anisotropic homoge-
standard. No other units of measurement are included in this
neous material, the airflow resistivity when the direction of
standard.
airflowisparalleltothefaceofthematerialfromwhichthetest
1.4.1 Table 1 is provided for user to convert into cgs units.
specimen is taken.
1.5 This standard does not purport to address all of the
3.2.4 specific airflow resistance, r; mks rayl (Pa·s/m)—the
safety concerns, if any, associated with its use. It is the
product of the airflow resistance of a specimen and its area.
responsibility of the user of this standard to establish appro-
This is equivalent to the air pressure difference across the
priate safety and health practices and determine the applica-
specimen divided by the linear velocity of airflow measured
bility of regulatory limitations prior to use.
outside the specimen.
3.2.5 transverse airflow resistivity— of an anisotropic ho-
2. Referenced Documents
mogeneous material, the airflow resistivity when the direction
2.1 ASTM Standards:
of airflow is perpendicular to the face of the material from
which the test specimen is taken.
ThistestmethodisunderthejurisdictionofASTMCommitteeE33onBuilding
3.3 Application of Terms:
and Environmental Acoustics and is the direct responsibility of Subcommittee
3.3.1 The term airflow resistance can be applied to speci-
E33.01 on Sound Absorption.
mens of any kind.
Current edition approved Oct. 1, 2009. Published February 2010. Originally
3.3.2 The term specific airflow resistance has meaning only
approved in 1963. Last previous edition approved in 2003 as C522 – 03. DOI:
10.1520/C0522-03R09E01.
when applied to a specimen of uniform thickness that is
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
homogeneous in directions parallel to its surface but not
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
necessarily homogeneous in the direction of airflow perpen-
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. dicular to its surface.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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C522−03 (2009)
TABLE 1 Conversion from cgs to mks and SI units
5. Significance and Use
To convert from to Multiply by
5.1 The specific airflow resistance of an acoustical material
3 5
cgs acoustic ohm mks acoustic ohm (Pa·s/m)10
is one of the properties that determine its sound-absorptive and
cgs rayl mks rayl (Pa·s/m) 10
2 3
sound-transmitting properties. Measurement of specific airflow
cgs rayl/cm mks rayl/m (Pa·s/m)10
cgs rayl/in. mks rayl/m (Pa·s/m ) 394
resistance is useful during product development, for quality
mks rayl/in. mks rayl/m (Pa·s/m ) 39.4
control during manufacture, and for specification purposes.
5.2 Valid measurements are made only in the region of
laminarairflowwhere,asidefromrandommeasurementerrors,
3.3.3 The term airflow resistivity has meaning only when
the airflow resistance (R=P⁄U) is constant. When the airflow
applied to a specimen that is homogeneous in directions
is turbulent, the apparent airflow resistance increases with an
parallel to a and perpendicular to its surface but not necessarily
increase of volume velocity and the term “airflow resistance”
isotropic.
does not apply.
3.4 Symbols:
5.3 The specific airflow resistance measured by this test
3.4.1 P = air pressure difference across test specimen, Pa.
methodmaydifferfromthespecificresistancemeasuredbythe
3.4.2 U = volume velocity of airflow through the specimen,
3 impedance tube method in Test Method E384 for two reasons.
m /s.
In the presence of sound, the particle velocity inside a porous
3.4.3 u = U/S = linear velocity of airflow outside the
material is alternating while in this test method, the velocity is
specimen, m/s.
2 constant and in one direction only. Also, the particle velocity
3.4.4 S = area of specimen, m.
inside a porous material is not the same as the linear velocity
3.4.5 T = thickness of specimen, m.
measured outside the specimen.
4. Summary of Test Method
6. Apparatus
4.1 Thistestmethoddescribeshowtomeasureasteadyflow
6.1 The apparatus, assembled as shown schematically in
of air through a test specimen, how to measure the air pressure
difference across the specimen, and how to measure the Fig. 1, consists of the following components:
volume velocity of airflow through the specimen. From the 6.1.1 Air Supply, a suction generator or positive air supply
measurements may be calculated the airflow resistance, R, the arranged to draw or force air at a uniform rate through the test
specific airflow resistance, r, and the airflow resistivity, r . specimen.
FIG. 1 Schematic Diagram of Airflow Apparatus
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C522−03 (2009)
NOTE 1—It may be necessary to use a large surge tank or other means
mounting plate has two holes for tube connections to the
to reduce pressure fluctuations.
pressure measuring device and to the airflow supply. The
6.1.2 Flowmeter, to measure the volume velocity of airflow
specimen holder, which is sealed to the mounting plate, is
through the specimen. It is preferable to have two or more preferably a transparent plastic tube at least 150 mm long with
flowmeters with overlapping ranges to enable different airflow
a diameter not less than 50 mm. For testing materials that will
velocities to be measured to the same precision.
support themselves, such as disks cut from boards, a slight
6.1.3 Differential Pressure Measuring Device, for measur-
taperatthetopofholderwillenablethespecimentobepressed
ing the static pressure difference between the faces of the
into position with a tight fit. For testing materials that will not
specimen with respect to atmosphere.
supportthemselves,aremovablescreenheldinpositionatleast
25 mm above the mounting plate may be used alone or with a
NOTE 2—Aslant manometer or pressure transducer system with a range
plunger assembly that can compress the specimen to a known
from 0 to 250 Pa is usually satisfactory, but a second instrument with a
smaller range, for example, 0 to 25 Pa, may be necessary for measuring thickness. For testing thin materials, such as fabrics or papers,
small pressures to the desired precision.
a flange at the top of the holder, together with a clamping ring,
will enable the specimen to be held securely for testing.
6.1.4 Specimen-Mounting Assembly, consists essentially of
amountingplateandaspecimenholderasshowninFig.2.The Specimens larger than the area of the holder can be tested with
FIG. 2 Specimen Holder
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C522−03 (2009)
suitable fittings attached to the end of the holder. In such cases, 10. Calculation
care must be taken to ensure that the airflow through the edges
10.1 Calculated the airflow resistance in mks acoustic ohms
of the specimen is negligible in comparison to that through the 3
(Pa·s/m ) from the expression:
face.
R 5 P/U (1)
NOTE 3—If measurements are made concurrently by the impedance
where P/Uistheaveragevalueoftenor
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