SIST EN ISO 9053-2:2020

SLOVENSKI STANDARD
oSIST prEN ISO 9053-2:2020
01-marec-2020
Akustika - Ugotavljanje upora pretoku zraka - 2. del: Metoda izmeničnega pretoka
zraka (ISO/DIS 9053-2:2020)
Acoustics - Determination of airflow resistance - Part 2: Alternating airflow method
(ISO/DIS 9053-2:2020)
Ta slovenski standard je istoveten z: prEN ISO 9053-2
ICS:
17.140.01 Akustična merjenja in Acoustic measurements and
blaženje hrupa na splošno noise abatement in general
91.100.60 Materiali za toplotno in Thermal and sound insulating
zvočno izolacijo materials
oSIST prEN ISO 9053-2:2020 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN ISO 9053-2:2020

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oSIST prEN ISO 9053-2:2020
DRAFT INTERNATIONAL STANDARD
ISO/DIS 9053-2
ISO/TC 43/SC 2 Secretariat: DIN
Voting begins on: Voting terminates on:
2020-01-09 2020-04-02
Acoustics — Determination of airflow resistance —
Part 2:
Alternating airflow method
ICS: 91.100.60
THIS DOCUMENT IS A DRAFT CIRCULATED
This document is circulated as received from the committee secretariat.
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
ISO/CEN PARALLEL PROCESSING
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 9053-2:2020(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
©
PROVIDE SUPPORTING DOCUMENTATION. ISO 2020

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COPYRIGHT PROTECTED DOCUMENT
© ISO 2020
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
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Contents
Foreword . iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviations . 3
5 Principle . 5
6 Equipment . 6
6.1 General . 6
6.2 Device for producing the alternating airflow . 6
6.3 Sound measuring device . 7
6.4 Vessel and measurement cell . 8
6.5 Device for measuring the static pressure . 8
6.6 Device for measuring the frequency of the piston . 8
7 Test specimens . 8
7.1 Shape . 8
7.2 Dimensions . 9
7.2.1 Lateral dimensions . 9
7.2.2 Thickness. 9
7.3 Number of test specimens . 9
8 Test procedure . 9
9 Uncertainty . 11
10 Test report . 12
Annex A (normative) Effective ratio of specific heats for air . 13
A.1 Adiabatic compression . 13
A.2 Correction for heat conduction. 13
A.3 Calculated example . 15
Annex B (informative) Acoustic model of the flow . 16
Annex C (informative) Calculation of uncertainty . 18
C.1 General . 18
C.2 Calculated example . 19
Annex D (informative) Airflow resistance of perforated support . 20
Bibliography . 21

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Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national
standards bodies (ISO member bodies). The work of preparing International Standards is normally
carried out through ISO technical committees. Each member body interested in a subject for which a
technical committee has been established has the right to be represented on that committee.
International organizations, governmental and non-governmental, in liaison with ISO, also take part in
the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all
matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 43, Acoustics, Subcommittee SC 2,
Building acoustics.
This standard cancels and replaces method B included in the first edition (ISO 9053:1991), which has
been technically revised.
The main changes compared to the previous edition are as follows:
— the requirement to the dimensions of the test specimen is changed;
— a correction for heat conduction is added.
A list of all parts in the ISO 9053 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
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oSIST prEN ISO 9053-2:2020
DRAFT INTERNATIONAL STANDARD ISO/DIS 9053-2:2020(E)
Acoustics — Determination of airflow resistance —
Part 2:
Alternating airflow method
1 Scope
This International Standard specifies an alternating airflow method for the determination of the airflow
resistance [1], [2] of porous materials for acoustical applications.
Determination of the airflow resistance based on static flow is described in ISO 9053-1.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 9053-1, Acoustics — Determination of airflow resistance — Part 1: Static airflow method
ISO/IEC Guide 98-3: Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in
measurement (GUM:1995)
IEC 61672-1, Electroacoustics — Sound level meters — Part 1: Specifications
IEC 61260-1, Electroacoustics — Octave-band and fractional-octave-band filters — Part 1: Specifications
IEC 61094-2:2009, Electroacoustics — Measurement microphones — Part 2: Primary method for the
pressure calibration of laboratory standard microphones by the reciprocity technique
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp
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3.1
airflow resistance
𝑹𝑹
quantity defined by
∆𝑝𝑝
𝑅𝑅 =
𝑞𝑞
v
where
∆𝑝𝑝 is the RMS air pressure difference, in pascal, across the test specimen due to the alternating
airflow;
𝑞𝑞 is the RMS volumetric airflow rate, in cubic metres per second, passing through the test
v
specimen
Note 1 to entry: Airflow resistance is expressed in pascal second per cubic metre.
3.2
specific airflow resistance
𝑹𝑹
𝐬𝐬
quantity defined by
𝑅𝑅 =𝑅𝑅⋅𝐴𝐴
s
where
𝑅𝑅 is the airflow resistance, in pascal second per cubic metre, of the test specimen;
𝐴𝐴 is the cross-section area, in square metre, of the test specimen perpendicular to the direction of
flow
Note 1 to entry: Specific airflow resistance is expressed in pascal second per metre.
3.3
airflow resistivity
𝝈𝝈
quantity defined by the following equation if the material is considered as being homogeneous
𝑅𝑅
s
𝜎𝜎 =
𝑑𝑑
where
𝑅𝑅 is the specific airflow resistance, in pascal second per metre, of the test specimen;
s
𝑑𝑑 is the thickness, in metre, of the test specimen in the direction of flow
Note 1 to entry: Airflow resistivity is expressed in pascal second per square metre.
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3.4
airflow velocity
𝒖𝒖
quantity defined by
𝑞𝑞
v
𝑢𝑢 =
𝐴𝐴
where
𝑞𝑞 is the RMS volumetric airflow rate, in cubic metre per second, passing through the test
v
specimen;
𝐴𝐴 is the cross-sectional area, in square metre, of the test specimen perpendicular to the direction
of flow
Note 1 to entry: Airflow velocity is expressed in metre per second.
3.5
Sound pressure level
𝑳𝑳
𝐩𝐩
ten times the logarithm to the base 10 of the ratio of the time average of the square of the sound
pressure, 𝑝𝑝(𝑡𝑡), during a stated time interval of duration, 𝑇𝑇 (starting at 𝑡𝑡 and ending at 𝑡𝑡 ), to the square
1 2
of a reference value, 𝑝𝑝 :
0
1 𝑡𝑡
2 2
( )
∫ 𝑝𝑝 𝑡𝑡 d𝑡𝑡
𝑡𝑡
𝑇𝑇
1
𝐿𝐿 = 10 lg� � dB
p
2
𝑝𝑝
0
where the reference value, 𝑝𝑝 , is 20 μPa
0
Note 1 to entry: The sound pressure level is expressed in decibel.
4 Symbols and abbreviations
R airflow resistance, in pascal second per metre, of the test specimen
𝑅𝑅 specific airflow resistance, in pascal second per metre, of the test specimen
s
𝑝𝑝 sound pressure, in µPa
𝑝𝑝 sound pressure reference value, 20 µPa
0
𝑝𝑝 sound pressure when the test cell with the test specimen is mounted
s
𝑝𝑝 sound pressure when the air cavity is closed by the airtight termination
t
∆𝑝𝑝 rms air pressure difference, in pascal, across the test specimen due to the alternating airflow
𝑃𝑃 static pressure, in Pa
s
𝑞𝑞 rms value of the volume flow when the test cell with the test specimen is mounted
s
𝑞𝑞 rms value of the volume flow when the air cavity is closed by the airtight termination
t
𝑞𝑞 rms volumetric airflow rate, in cubic metres per second, passing through the test specimen
v
u airflow velocity, in metre per second
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𝑢𝑢 rms-value of the airflow velocity through the test specimen, in metre per second
s
𝐿𝐿 sound pressure level, in decibels
p
𝐿𝐿
background sound pressure level, in decibels
p,b
𝐿𝐿 sound pressure level in the air cavity when the measurement cell with the test specimen is
p,s
mounted, in decibels
𝐿𝐿 sound pressure level in the air cavity with the airtight termination, in decibels
p,t
d thickness, in metre, of the test specimen in the direction of flow
A cross-section area, in square metre, of the test specimen
𝐴𝐴 cross sectional area of the piston, m²
P
𝜎𝜎 airflow resistivity, in pascal second per metre, of the test specimen
f frequency of the piston movement, in Hz
h amplitude of the stroke of the piston, in m
ℎ amplitude of the stroke of the piston when the air cavity is closed by the airtight termination,
t
in m
ℎ amplitude of the stroke of the piston when the measurement cell with the test specimen is
s
mounted, in m
𝜅𝜅 ratio of specific heats for air
𝜅𝜅′ effective ratio of specific heats for air
V volume of the air cavity with the airtight termination, in m³
b thickness of the thermal boundary layer
−3 −1
𝑍𝑍 acoustic impedance of the cavity, in Pa⋅ m ⋅ s
a
𝑐𝑐 speed of sound, in metres per seconds
0
𝑙𝑙 characteristic thermal diffusion length, in metres
h
−1 −1 −1
𝑘𝑘 thermal conductivity, in J⋅ m ⋅ s ⋅ K
a
−3
𝜌𝜌 density of air, in kg⋅ m
0
−1 −1
𝐶𝐶 specific heat capacity at constant pressure, in J⋅ kg ⋅ K
P
j
√−1
𝜔𝜔 circular frequency, 2⋅𝜋𝜋⋅𝑓𝑓
2
S total area, in m
λ wavelength, in m
N acoustic compliance
r ratio between the stroke amplitudes
u standard uncertainty
U expanded uncertainty
y thickness of the support in metres
η dynamic viscosity of air, in Pa s
𝜙𝜙 perforation rate
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5 Principle
An alternating volume flow with a low frequency, 𝑓𝑓, for example of 2 Hz, is generated by a piston or
similar device (see Figure 1 and Figure 2) moving sinusoidally. This volume flow acts on an air cavity
which is either closed by an airtight termination or terminated by the test specimen mounted in a
measurement cell. The sound pressure level is measured in the air cavity for both cases.
The pressure inside the cavity will be the outside atmospheric pressure modulated by the alternating
flow generated by the piston. The microphone mounted inside the cavity will therefore measure the
pressure difference across the specimen when the test cell with the specimen is mounted.
When the air cavity is closed, the volume flow creates a sound pressure in the air cavity which may be
calculated from the piston movement, dimensional information of the cavity and the atmospheric air
pressure.
When the measurement cell is mounted, the main part of the generated volume flow passes through the
test specimen and a lower sound pressure is observed in the air cavity. The difference between the
sound pressure levels when the vessel is closed and when the test cell is mounted is a direct function of
the airflow resistivity of the test specimen. By the measurement of the sound pressure differences, the
airflow resistance for the test specimen may be computed.
It can be practical to use different piston stroke lengths for the closed vessel and when the test cell is
mounted.

Key
1 Vessel 2 Air cavity
3 Piston 4 Microphone
5 Seal 6 Measurement cell
7 Test specimen 8 Optional support for test specimen
Figure 1 — Basic principle, termination with the test specimen
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Key
1 Vessel 2 Air cavity
3 Piston 4 Microphone
5 Seal 6 Airtight termination
Figure 2 — Basic principle, termination with an airtight seal

NOTE For materials with a visco-inertial transition frequency below 100 Hz the method described in ISO
9053-1 using static flow may give a different result. Examples of such materials are: a) fibre materials with large
fibres like some metal or plant fibres, b) foams with low porosity but big pores like some metal foams, c) granular
materials with large grains and low porosity like road pavements.
6 Equipment
6.1 General
The equipment shall consist of
a) a device for producing the alternating airflow;
b) a sound level meter or an alternative device for measuring the sound pressure level in a narrow
frequency band (e.g. a fractional-octave band) around the frequency of the piston;
c) a vessel
− containing the air cavity,
− allowing connections to the microphone and the source of the alternating airflow,
− including an airtight termination and a measurement cell;
d) a device for measuring the static pressure;
e) a device for measuring the frequency of the piston;
f) a device for measuring the thickness of the test specimen when it is in position for the test.
6.2 Device for producing the alternating airflow
The alternating airflow shall be produced by a sinusoidally moving piston. The frequency of the piston
movement, 𝑓𝑓, shall be in the range 1 Hz to 4 Hz and known with sufficient accuracy (see Annex C). The
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amplitude of the piston stroke ℎ (see Figure 1 and Figure 2) is to be determined, normally by
dimensional measurements. The rms-value of the volume flow, 𝑞𝑞 , produced by the moving piston is
v
𝑞𝑞 =√2⋅𝜋𝜋⋅𝑓𝑓⋅ℎ⋅𝐴𝐴
v P
where
𝑓𝑓 is the frequency of the piston movement, in Hz;
ℎ is the amplitude of the stroke of the piston in m;
𝐴𝐴 is the cross sectional area of the piston, in m².
P
Different stroke lengths may be applied for the measurement with the airtight termination and the test
cell with specimen. The two lengths should be selected to obtain suitable sound pressure levels in both
situations as well as generating the required airflow velocity through the specimen.
ℎ is the amplitude of the stroke of the piston when the air cavity is closed by the airtight
t
termination;
ℎ is the amplitude of the stroke of the piston when the measurement cell with the test specimen
s
is mounted.
The rms-value of the flow velocity through the test specimen in m/s is calculated according to
Formula (1):
√2⋅𝜋𝜋⋅𝑓𝑓⋅ℎ ⋅𝐴𝐴
s P
(1)
𝑢𝑢 =
s
𝐴𝐴
where 𝐴𝐴 is the cross-sectional area of the test specimen, in m², perpendicular to the direction of flow. It
−4 −3
is recommended to use rms-values of the flow velocity between 5 · 10 m/s and 4 · 10 m/s.
NOTE 1 A piston with a diameter of 10 mm and stroke lengths of 1,4 mm (airtight termination) and 14 mm
(measurement cell with specimen) has proven to be appropriate for a measurement cell diameter of 100 mm and
−3 3
an air cavity with a volume of about 10 m .
NOTE 2 The use of different piston frequencies and stroke lengths can be used to demonstrate that the
obtained airflow resistance is independent of the airflow velocity.
NOTE 3 The uncertainty analysis shows that the ratio between the different applied stroke lengths is
important. The ratio can be verified by using a sound level measuring system that covers the pressures generated
by all the applied strokes lengths.
6.3 Sound measuring device
The sound measuring device shall be able to measure sound pressure with the piston frequency. The
applied sound pressure shall be within the linear measurement range for the device.
The sound measuring device shall have a small bandwidth around the piston frequency for reducing
background noise and harmonic distortions.
For all related measurements at a particular piston frequency including measurement of background
noise, the bandwidth of the sound measuring device shall not be changed.
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The sound measuring device may be a sound level meter, including microphones and cables,
conforming to the requirements of IEC 61672-1 class 1 or class 2, and with fractional-octave band filters
meeting the requirements of IEC 61260-1 class 1 or class 2.
NOTE 1 The sound measuring device is mainly used to determine the difference in sound pressure levels for
sound with a constant frequency. Level linearity performance at this frequency is therefore the most important
property.
NOTE 2 It is important that sound measuring device only measures the sound with frequencies close to the
frequency of the piston in order to reduce the effect of harmonic distortions and background noise. The band
limiting function can be obtained by the use of a fractional-octave band filter or FFT-analyser/technique.
6.4 Vessel and measurement cell
The vessel and the measurement cell shall be in the shape of a circular cylinder or a rectangular
parallelepiped (preferably with a square cross-section in the latter case). The vessel shall include
appropriate seals to enable a leak free mounting of the airtight termination and the measurement cell.
The vessel and the airtight termination shall be sufficiently stiff to avoid volume changes under
alternating pressure conditions. The volume 𝑉𝑉 of the air cavity inside the closed vessel with the airtight
termination mounted shall include all connecting pipes such as to the microphone and to the piston.
The piston shall be in centre position when the volume is measured.
The diameter or smallest edge of the measurement cell shall be chosen depending on the specimens to
test. In any case, the minimum diameter or smallest edge of the measurement cell shall be 29 mm.
Furthermore, the air cavity shall have a cross section which is at least the same as the cross section of
the measurement cell. Various measurement cells can be used as long as they fulfil all the requirements
of this standard.
The vessel and the measurement cell should be made such that the airflow is along the flow direction to
be measured. This is normally perpendicular to the surface of the specimen to be measured. The
measurement cell may include two grills or perforated plates for keeping the test specimen in position.
It is important that the test specimen do not move due to the alternating air flow. The supports shall
have an open area of minimum 50 %, evenly distributed. The holes in the support shall have a diameter
of not less than 3 mm. The airflow resistance of the support should be less than 1 % of the airflow
resistance to be measured. See informative Annex D for information.
6.5 Device for measuring the static pressure
The device for measuring the static pressure shall be capable of performing measurements with a low
uncertainty. The uncertainty in the static pressure shall be considered in the uncertainty budget.
6.6 Device for measuring the frequency of the piston
The frequency of the piston shall be determined with low uncertainty. The uncertainty in the frequency
shall be considered in the uncertainty budget. The frequency may be measured from the microphone
signal by the use of a frequency counter or by frequency analysis.
7 Test specimens
7.1 Shape
The test specimen may be circular or rectangular, corresponding to the shape of the measurement cell.
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7.2 Dimensions
7.2.1 Lateral dimensions
The lateral dimensions of a specimen shall contain a minimum of 10 pores for a foam specimen,
10 fibres for a fibrous material specimen, 10 grains for a granular specimen. In case no information
about the microstructure of the material (number of pores, fibres or grains per millimetre) is available,
a minimum diameter of 95 mm or a smaller edge of 90 mm minimum is required for the material
specimens.
The measurement cell shall have the same lateral dimensions as the material specimen to test. See 7.2
to avoid leaks between the measurement cell and the specimen.
Care should be taken to avoid dimensional distortion of the test specimen.
7.2.2 Thickness
The thickness of the test specimen shall be chosen to obtain a measurable sound pressure level above
self-noise in the instrument and noise in the environment.
The test specimen shall be mounted in the measurement cell in a way to prevent altering the thickness
of the specimen.
If the test specimens available are not sufficiently thick to produce a suitable sound pressure level, test
specimens chosen in the same way, may be superimposed if it does not modify the material microscopic
structure. In particular, when test specimens of fibrous materials or non-woven textiles are
superimposed, the same orientation of the fibres shall be used for the individual superimposed
specimens. For perforated plates or woven textiles, holes or patterns should all be superimposed.
7.3 Number of test specimens
The required number of test specimens depends on the type of the material and is commonly defined in
product standards. Usually three to six samples are required.
8 Test procedure
7.1 Place the test specimen, prepared as described in Clause 6, in the measurement cell.
7.2 Ensure that the edges are properly sealed. A thin layer of petroleum jelly, thread seal tape or rings
may be used to seal the edges of specimens. When using petroleum jelly, care should be taken to avoid
penetration of the petroleum jelly inside the material specimen.
7.3 Bring the device for measuring the thickness of the test specimens into contact with the upper
surface of the test specimens, compressing it lightly if necessary.
7.4 Note the thickness and use this measurement to determine the free or the compressed volume
and from this derive the free or the compressed density of the test specimen when in position.
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7.5 Measure the static pressure 𝑃𝑃 . Adjust the volume flo
...