ASTM C522-03(2022)
(Test Method)Standard Test Method for Airflow Resistance of Acoustical Materials
Standard Test Method for Airflow Resistance of Acoustical Materials
SIGNIFICANCE AND USE
5.1 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.
5.2 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.
5.3 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 mm/s to 50 mm/s and pressure differences across the specimen ranging from 0.1 Pa 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.
cgs acoustic ohm
mks acoustic ohm (Pa·s/m3)
105
cgs rayl
mks rayl (Pa·s/m)
10
cgs rayl/cm
mks rayl/m (Pa·s/m2)
103
cgs rayl/in.
mks rayl/m (Pa·s/m2)
394
mks rayl/in.
mks rayl/m (Pa·s/m2)
39.4
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
Relations
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation:C522 −03 (Reapproved 2022)
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.
1. Scope 2. Referenced Documents
2.1 ASTM Standards:
1.1 This test method covers the measurement of airflow
E384 Test Method for Microindentation Hardness of Mate-
resistance and the related measurements of specific airflow
rials
resistanceandairflowresistivityofporousmaterialsthatcanbe
C634 Terminology Relating to Building and Environmental
used for the absorption and attenuation of sound. Materials
Acoustics
cover a range from thick boards or blankets to thin mats,
E691 Practice for Conducting an Interlaboratory Study to
fabrics, papers, and screens. When the material is anisotropic,
Determine the Precision of a Test Method
provision is made for measurements along different axes of the
specimen.
3. Terminology
1.2 This test method is designed for the measurement of
3.1 Definitions: The definitions used in this test method are
values of specific airflow resistance ranging from 100 to
contained in Terminology C634.
10 000 mks rayls (Pa·s/m) with linear airflow velocities rang-
3.2 Definitions of Terms Specific to This Standard: The
ing from 0.5 mm⁄s to 50 mm⁄s and pressure differences across
following items have been modified to exclude alternating
the specimen ranging from 0.1 Pa to 250 Pa.The upper limit of
flow.
this range of linear airflow velocities is a point at which the
3.2.1 airflow resistance, R; mks acoustic ohm
airflow through most porous materials is in partial or complete
(Pa·s/m )—the quotient of the air pressure difference across a
transition from laminar to turbulent flow.
specimendividedbythevolumevelocityofairflowthroughthe
specimen.
1.3 A procedure for accrediting a laboratory for the pur-
3.2.2 airflow resistivity, r ; mks rayl/m (Pa·s/m )—ofa
poses of this test method is given in Annex A1.
homogeneous material, the quotient of its specific airflow
1.4 The values stated in SI units are to be regarded as
resistance divided by its thickness.
standard. No other units of measurement are included in this
3.2.3 lateral airflow resistivity— of an anisotropic homoge-
standard.
neous material, the airflow resistivity when the direction of
1.4.1 Table 1 is provided for user to convert into cgs units.
airflowisparalleltothefaceofthematerialfromwhichthetest
1.5 This standard does not purport to address all of the specimen is taken.
safety concerns, if any, associated with its use. It is the
3.2.4 specific airflow resistance, r; mks rayl (Pa·s/m)—the
responsibility of the user of this standard to establish appro-
product of the airflow resistance of a specimen and its area.
priate safety, health, and environmental practices and deter-
This is equivalent to the air pressure difference across the
mine the applicability of regulatory limitations prior to use.
specimen divided by the linear velocity of airflow measured
1.6 This international standard was developed in accor-
outside the specimen.
dance with internationally recognized principles on standard-
3.2.5 transverse airflow resistivity— of an anisotropic ho-
ization established in the Decision on Principles for the
mogeneous material, the airflow resistivity when the direction
Development of International Standards, Guides and Recom-
of airflow is perpendicular to the face of the material from
mendations issued by the World Trade Organization Technical
which the test specimen is taken.
Barriers to Trade (TBT) Committee.
3.3 Application of Terms:
3.3.1 The term airflow resistance can be applied to speci-
mens of any kind.
ThistestmethodisunderthejurisdictionofASTMCommitteeE33onBuilding
and Environmental Acoustics and is the direct responsibility of Subcommittee
E33.01 on Sound Absorption. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Oct. 1, 2022. Published October 2022. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1963. Last previous edition approved in 2016 as C522 – 03 (2016). Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/C0522-03R22. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C522−03 (2022)
TABLE 1 Conversion from cgs to mks and SI units
6.1.1 Air Supply, a suction generator or positive air supply
To convert from to Multiply by arranged to draw or force air at a uniform rate through the test
3 5
specimen.
cgs acoustic ohm mks acoustic ohm (Pa·s/m)10
cgs rayl mks rayl (Pa·s/m) 10
2 3
NOTE 1—It may be necessary to use a large surge tank or other means
cgs rayl/cm mks rayl/m (Pa·s/m)10
cgs rayl/in. mks rayl/m (Pa·s/m ) 394 to reduce pressure fluctuations.
mks rayl/in. mks rayl/m (Pa·s/m ) 39.4
6.1.2 Flowmeter, to measure the volume velocity of airflow
through the specimen. It is preferable to have two or more
flowmeters with overlapping ranges to enable different airflow
3.3.2 The term specific airflow resistance has meaning only
velocities to be measured to the same precision.
when applied to a specimen of uniform thickness that is
6.1.3 Differential Pressure Measuring Device, for measur-
homogeneous in directions parallel to its surface but not
ing the static pressure difference between the faces of the
necessarily homogeneous in the direction of airflow perpen-
specimen with respect to atmosphere.
dicular to its surface.
3.3.3 The term airflow resistivity has meaning only when NOTE 2—Aslant manometer or pressure transducer system with a range
from 0 Pa to 250 Pa is usually satisfactory, but a second instrument with
applied to a specimen that is homogeneous in directions
a smaller range, for example, 0 Pa to 25 Pa, may be necessary for
parallel to a and perpendicular to its surface but not necessarily
measuring small pressures to the desired precision.
isotropic.
6.1.4 Specimen-Mounting Assembly, consists essentially of
3.4 Symbols:
amountingplateandaspecimenholderasshowninFig.2.The
3.4.1 P = air pressure difference across test specimen, Pa.
mounting plate has two holes for tube connections to the
3.4.2 U = volume velocity of airflow through the specimen,
pressure measuring device and to the airflow supply. The
m /s.
specimen holder, which is sealed to the mounting plate, is
3.4.3 u = U/S = linear velocity of airflow outside the
preferably a transparent plastic tube at least 150 mm long with
specimen, m/s.
a diameter not less than 50 mm. For testing materials that will
3.4.4 S = area of specimen, m.
support themselves, such as disks cut from boards, a slight
3.4.5 T = thickness of specimen, m.
taperatthetopofholderwillenablethespecimentobepressed
4. Summary of Test Method into position with a tight fit. For testing materials that will not
supportthemselves,aremovablescreenheldinpositionatleast
4.1 Thistestmethoddescribeshowtomeasureasteadyflow
25 mm above the mounting plate may be used alone or with a
of air through a test specimen, how to measure the air pressure
plunger assembly that can compress the specimen to a known
difference across the specimen, and how to measure the
thickness. For testing thin materials, such as fabrics or papers,
volume velocity of airflow through the specimen. From the
a flange at the top of the holder, together with a clamping ring,
measurements may be calculated the airflow resistance, R, the
will enable the specimen to be held securely for testing.
specific airflow resistance, r, and the airflow resistivity, r .
Specimens larger than the area of the holder can be tested with
suitable fittings attached to the end of the holder. In such cases,
5. Significance and Use
care must be taken to ensure that the airflow through the edges
5.1 The specific airflow resistance of an acoustical material
of the specimen is negligible in comparison to that through the
is one of the properties that determine its sound-absorptive and
face.
sound-transmitting properties. Measurement of specific airflow
resistance is useful during product development, for quality
NOTE 3—If measurements are made concurrently by the impedance
tube method, Test Method E384, the two instruments may conveniently
control during manufacture, and for specification purposes.
have the same inside diameter.
5.2 Valid measurements are made only in the region of
laminar airflow where, aside from random measurement errors, 7. Sampling
the airflow resistance (R=P⁄U) is constant. When the airflow
7.1 Three or more specimens of a uniform sample material
is turbulent, the apparent airflow resistance increases with an
should be tested. When the sample is not uniform the speci-
increase of volume velocity and the term “airflow resistance”
mens should be selected to include the variations in the proper
does not apply.
proportion,orseveralrepresentativespecimensofthematerials
5.3 The specific airflow resistance measured by this test should be tested and the results averaged.
methodmaydifferfromthespecificresistancemeasuredbythe
8. Test Specimens
impedance tube method in Test Method E384 for two reasons.
In the presence of sound, the particle velocity inside a porous 8.1 Boards—Relatively hard, firm materials at least 5 mm
material is al
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