SIST EN ISO 9053-2:2020

Acoustics - Determination of airflow resistance - Part 2: Alternating airflow method (ISO 9053-2:2020)

This document specifies an alternating airflow method for the determination of the airflow resistance[5], [6] of porous materials for acoustical applications.
Determination of the airflow resistance based on static flow is described in ISO 9053‑1.

Akustik - Bestimmung des Strömungswiderstandes - Teil 2: Alternierendes Strömungsverfahren (ISO 9053-2:2020)

Dieses Dokument legt ein Luftwechselstromverfahren zur Bestimmung des Strömungswiderstandes [5] [6] von porösen Materialien für akustische Anwendungen fest.
Die Bestimmung des Strömungswiderstandes auf der Grundlage einer statischen Luftströmung wird in ISO 9053 1 beschrieben.

Acoustique - Détermination de la résistance à l’écoulement de l’air - Partie 2: Méthode avec écoulement d’air alternatif (ISO 9053-2:2020)

Le présent document spécifie une méthode avec écoulement d'air alternatif pour la détermination de la résistance à l'écoulement de l'air[5][6] des matériaux poreux utilisés pour les applications acoustiques.
La détermination de la résistance à l'écoulement de l'air reposant sur un écoulement statique est décrite dans l'ISO 9053-1.

Akustika - Ugotavljanje upornosti zračnemu toku - 2. del: Metoda izmeničnega zračnega toka (ISO 9053-2:2020)

General Information

• Status: Published
• Public Enquiry End Date: 19-Mar-2020
• Publication Date: 15-Nov-2020
• ICS: 17.140.01 - Acoustic measurements and noise abatement in general
• ICS: 91.100.60 - Thermal and sound insulating materials
• Technical Committee: AKU - Acoustics
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 19-Oct-2020
• Due Date: 24-Dec-2020
• Completion Date: 16-Nov-2020
• Ref Project: EN ISO 9053-2:2020 - Acoustics - Determination of airflow resistance - Part 2: Alternating airflow method (ISO 9053-2:2020)

Overview

EN ISO 9053-2:2020 - Acoustics: Determination of airflow resistance (Part 2: Alternating airflow method) specifies an alternating airflow method for measuring the airflow resistance of porous materials used in acoustical applications. Published by CEN/ISO in 2020, this part complements ISO 9053‑1 (static flow method) and provides the test principle, required equipment, specimen preparation rules, measurement procedure, uncertainty estimation and reporting requirements.

Key topics and requirements

• Scope and purpose: Measurement of airflow resistance (R), expressed as the ratio of RMS pressure difference across a specimen to RMS volumetric flow (Δp / q), for porous acoustical materials.
• Definitions and symbols: Clear definitions for airflow resistance, specific airflow resistance (Rs), airflow resistivity (σ), airflow velocity, sound pressure level and related quantities; reference sound pressure is 20 μPa.
• Principle: Uses an alternating (oscillatory) airflow generated by a piston or similar device; the method records RMS pressure and volumetric flow in a measurement cell to obtain R.
• Equipment requirements:
  • Device producing alternating airflow (piston or equivalent)
  • Sound measuring device and pressure sensors
  • Measurement cell / vessel and airtight termination
  • Devices to measure static pressure and piston frequency
• Test specimens: Guidance on homogeneity, shape, lateral dimensions and thickness; number of specimens to be tested.
• Procedure and corrections: Step‑by‑step test procedure, thermal conduction correction and acoustic modelling considerations to ensure accurate results.
• Uncertainty and reporting: Annexes provide calculation of measurement uncertainty (GUM guidance), and required content for test reports.
• Informative annexes: Effective ratio of specific heats for air, acoustic flow models, uncertainty calculation examples, and treatment of airflow resistance with perforated supports.

Applications and practical value

• Characterizing porous absorbers, insulation, and acoustic liners for product development and quality control.
• Specifying material input parameters for acoustic modelling, room acoustics design and sound-absorbing product selection.
• Verifying compliance with acoustic performance claims in manufacturing and certification.
• Useful in R&D, test laboratories, façade and building acoustics, HVAC silencer design and automotive/transport acoustic component testing.

Who should use this standard

• Acoustical engineers and consultants
• Materials and insulation manufacturers
• Accredited test laboratories and metrology institutes
• Product certification bodies and building acoustics specialists
• R&D teams developing sound-absorbing materials

Related standards

• ISO 9053‑1 - Determination of airflow resistance by static flow (complements Part 2)
• ISO/IEC Guide 98‑3 (GUM) - Guide for expression of measurement uncertainty

Keywords: EN ISO 9053-2:2020, alternating airflow method, airflow resistance, airflow resistivity, acoustics, porous materials, specific airflow resistance, ISO 9053.

Standards Content (Sample)

SLOVENSKI STANDARD
01-december-2020
Akustika - Ugotavljanje upornosti zračnemu toku - 2. del: Metoda izmeničnega
zračnega toka (ISO 9053-2:2020)
Acoustics - Determination of airflow resistance - Part 2: Alternating airflow method (ISO
9053-2:2020)
Akustik - Bestimmung des Strömungswiderstandes - Teil 2: Alternierendes
Strömungsverfahren (ISO 9053-2:2020)
Acoustique - Détermination de la résistance à l’écoulement de l’air - Partie 2: Méthode
avec écoulement d’air alternatif (ISO 9053-2:2020)
Ta slovenski standard je istoveten z: EN ISO 9053-2:2020
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
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 9053-2
EUROPEAN STANDARD
NORME EUROPÉENNE
October 2020
EUROPÄISCHE NORM
ICS 91.100.60
English Version
Acoustics - Determination of airflow resistance - Part 2:
Alternating airflow method (ISO 9053-2:2020)
Acoustique - Détermination de la résistance à Akustik - Bestimmung des Strömungswiderstandes -
l'écoulement de l'air - Partie 2: Méthode avec Teil 2: Alternierendes Strömungsverfahren (ISO 9053-
écoulement d'air alternatif (ISO 9053-2:2020) 2:2020)
This European Standard was approved by CEN on 22 September 2020.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 9053-2:2020 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 9053-2:2020) has been prepared by Technical Committee ISO/TC 43
"Acoustics" in collaboration with Technical Committee CEN/TC 126 “Acoustic properties of building
elements and of buildings” the secretariat of which is held by AFNOR.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by April 2021, and conflicting national standards shall be
withdrawn at the latest by April 2021.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
Endorsement notice
The text of ISO 9053-2:2020 has been approved by CEN as EN ISO 9053-2:2020 without any
modification.
INTERNATIONAL ISO
STANDARD 9053-2
First edition
2020-09
Acoustics — Determination of airflow
resistance —
Part 2:
Alternating airflow method
Acoustique — Détermination de la résistance à l’écoulement de l’air —
Partie 2: Méthode avec écoulement d’air alternatif
Reference number
ISO 9053-2:2020(E)
©
ISO 2020
ISO 9053-2:2020(E)
© 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
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved

ISO 9053-2:2020(E)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3  Terms and definitions . 1
4  Symbols . 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 . 7
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 Homogeneity of test specimen . 8
7.2 Shape . 8
7.3 Dimensions . 8
7.3.1 Lateral dimensions . . 8
7.3.2 Thickness . 9
7.4 Number of test specimens . 9
8  Test procedure . 9
9 Uncertainty .10
10 Test report .11
Annex A (normative) Effective ratio of specific heats for air .12
Annex B (informative) Acoustic model of the flow .15
Annex C (informative) Calculation of uncertainty .17
Annex D (informative) Airflow resistance of perforated support .19
Bibliography .20
ISO 9053-2:2020(E)
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 first edition of ISO 9053-2, together with ISO 9053-1:2018, cancels and replaces ISO 9053:1991,
which has been technically revised.
The main changes compared to the previous edition are as follows:
— the former method B in ISO 9053:1991 has been transferred to this document;
— the requirement to the dimensions of the test specimen have been updated;
— a correction for heat conduction has been 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.
iv © ISO 2020 – All rights reserved

INTERNATIONAL STANDARD ISO 9053-2:2020(E)
Acoustics — Determination of airflow resistance —
Part 2:
Alternating airflow method
1 Scope
This document specifies an alternating airflow method for the determination of the airflow
[5], [6]
resistance 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/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in
me a s ur ement (GUM: 1995)
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:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
airflow resistance
R
quantity defined by
Dp
R=
q
v
where
Dp
is the RMS air pressure difference, across the test specimen, due to the alternating airflow,
in pascals;
q is the RMS volumetric airflow rate, passing through the test specimen, in cubic metres
v
per second.
Note 1 to entry: Airflow resistance is expressed in pascals seconds per cubic metre.
ISO 9053-2:2020(E)
3.2
specific airflow resistance
R
s
quantity defined by
RR=⋅A
s
where
R
is the airflow resistance of the test specimen, in pascals seconds per cubic metre;
A
is the cross-section area of the test specimen, perpendicular to the direction of flow, in
square metres.
Note 1 to entry: Specific airflow resistance is expressed in pascals seconds per metre.
3.3
airflow resistivity
σ
quantity defined by the following formula if the material is considered as being homogeneous
R
s
σ=
d
where
R is the specific airflow resistance of the test specimen, in pascals seconds per metre;
s
d
is the thickness of the test specimen, in the direction of flow, in metres.
Note 1 to entry: Airflow resistivity is expressed in pascals seconds per square metre.
3.4
airflow velocity
v
quantity defined by
q
v
v=
A
where
q is the RMS volumetric airflow rate, passing through the test specimen, in cubic metres per
v
second;
A
is the cross-sectional area of the test specimen, perpendicular to the direction of flow, in
square metres.
Note 1 to entry: Airflow velocity is expressed in metres per second.
2 © ISO 2020 – All rights reserved

ISO 9053-2:2020(E)
3.5
sound pressure level
L
p
ten times the logarithm to the base 10 of the ratio of the time average of the square of the sound
pressure, pt() , during a stated time interval of duration, T (starting at t and ending at t ), to the
1 2
square of a reference value, p :
t
 2 
pt()dt
 ∫ 
t
T
L =10lg dB
p
 p 
 
 
where the reference value, p , is 20 μPa
Note 1 to entry: The sound pressure level is expressed in decibels.
4  Symbols
A cross-section area of the test specimen, in square metres;
A cross sectional area of the piston, in square metres;
P
b thickness of the thermal boundary layer, in metres;
C specific heat capacity at constant pressure, in joules per kilogram and degree kelvin;
P
c speed of sound, in metres per second;
d thickness of the test specimen, in the direction of flow, in metres;
f frequency of the piston movement, in hertz;
h amplitude of the stroke of the piston, in metres;
h
amplitude of the stroke of the piston when the measurement cell with the test specimen is
s
mounted, in metres;
h amplitude of the stroke of the piston when the air cavity is closed by the airtight termina-
t
tion, in metres;
j
−1
k thermal conductivity, in joules per meter, second and degree kelvin;
a
L sound pressure level, in decibels;
p
L background sound pressure level, in decibels;
pb,
L
sound pressure level in the air cavity when the measurement cell with the test specimen is
ps,
mounted, in decibels;
L sound pressure level in the air cavity with the airtight termination, in decibels;
pt,
l characteristic thermal diffusion length, in metres;
h
N acoustic compliance, in cubic metres per pascal;
P static pressure, in pascals;
S
ISO 9053-2:2020(E)
p
sound pressure, in pascals;
p
sound pressure when the test cell with the test specimen is mounted, in pascals;
s
p sound pressure when the air cavity is closed by the airtight termination, in pascals;
t
p sound pressure reference value, 20 µPa;
q rms value of the volume flow when the test cell with the test specimen is mounted, in cubic
s
metres per second;
q rms value of the volume flow when the air cavity is closed by the airtight termination, in
t
cubic metres per second;
q rms volumetric airflow rate, passing through the test specimen, in cubic metres per second;
v
R airflow resistance of the test specimen, in pascals seconds per cubic metre;
R specific airflow resistance of the test specimen, in pascals seconds per metre;
s
r ratio between the stroke amplitudes;
r radius of the perforations in the specimen support (Annex D), in metres;
r
S total area, in square metres;
U expanded uncertainty;
u standard uncertainty;
V volume of the air cavity with the airtight termination, in cubic metres;
v airflow velocity, in metres per second;
v rms-value of the airflow velocity through the test specimen, in metres per second;
s
y thickness of the support, in metres;
Z acoustic impedance of the cavity, in pascals seconds per cubic metres;
a
Dp
rms air pressure difference, across the test specimen, due to the alternating airflow, in
pascals;
φ
perforation rate;
η dynamic viscosity of air, in pascals seconds;
κ
ratio of specific heats for air;
κ '
effective ratio of specific heats for air;
λ wavelength, in metres;
ρ density of air, in kilograms per cubic metre;
σ
airflow resistivity of the test specimen, in pascals seconds per square metre;
ω
circular frequency, 2 · π · f, in per second.
4 © ISO 2020 – All rights reserved

ISO 9053-2:2020(E)
5  Principle
An alternating volume flow with a low frequency, f , 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
that 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 is the outside atmospheric pressure modulated by the alternating flow
generated by the piston. The microphone mounted inside the cavity therefore measures 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 that can be
calculated from the piston movement, the 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 can be computed.
It can be practical to use different piston stroke lengths for the closed vessel and when the measurement
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
ISO 9053-2:2020(E)
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 a static flow can give a different result. Examples of such materials are: a) fibre materials with
large fibres, such as some metal or plant fibres, b) foams with low porosity but big pores, such as some metal
foams, c) granular materials with large grains and low porosity, such as road pavements.
6 Equipment
6.1  General
The equipment shall consist of:
a) a device for producing the alternating airflow (see 6.2);
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 (see 6.3);
c) a vessel (see 6.4)
— containing the air cavity,
— allowing connections to the microphone and the source of the alternating airflow, and
— including an airtight termination and a measurement cell;
d) a device for measuring the static pressure (see 6.5);
e) a device for measuring the frequency of the piston (see 6.6);
f) a device for measuring the thickness of the test specimen when it is positioned 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, f , shall be in the range of 1 Hz to 4 Hz and known with sufficient accuracy (see Annex C).
6 © ISO 2020 – All rights reserved

ISO 9053-2:2020(E)
The amplitude of the piston stroke, h (see Figure 1 and Figure 2), shall be determined, normally by
dimensional measurements. The rms-value of the volume flow, q , produced by the moving piston is
v
qf=⋅2 π⋅⋅hA⋅
vP
Different stroke lengths can be applied for the measurement with the airtight termination and the
measurement cell with specimen. The two lengths shall be selected to obtain suitable sound pressure
levels in both situations as well as to generate the required airflow velocity through the specimen. 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.
The rms-value of the flow velocity through the test specimen, in metres per second, is calculated
according to Formula (1):
2⋅⋅π fh⋅⋅A
sP
v = (1)
s
A
−4 -1 −−31
It is recomm
...

SLOVENSKI STANDARD
01-december-2020
Akustika - Ugotavljanje upora pretoku zraka - 2. del: Metoda izmeničnega pretoka
zraka (ISO 9053-2:2020)
Acoustics - Determination of airflow resistance - Part 2: Alternating airflow method (ISO
9053-2:2020)
Akustik - Bestimmung des Strömungswiderstandes - Teil 2: Alternierendes
Strömungsverfahren (ISO 9053-2:2020)
Acoustique - Détermination de la résistance à l’écoulement de l’air - Partie 2: Méthode
avec écoulement d’air alternatif (ISO 9053-2:2020)
Ta slovenski standard je istoveten z: EN ISO 9053-2:2020
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
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 9053-2
EUROPEAN STANDARD
NORME EUROPÉENNE
October 2020
EUROPÄISCHE NORM
ICS 91.100.60
English Version
Acoustics - Determination of airflow resistance - Part 2:
Alternating airflow method (ISO 9053-2:2020)
Acoustique - Détermination de la résistance à Akustik - Bestimmung des Strömungswiderstandes -
l'écoulement de l'air - Partie 2: Méthode avec Teil 2: Alternierendes Strömungsverfahren (ISO 9053-
écoulement d'air alternatif (ISO 9053-2:2020) 2:2020)
This European Standard was approved by CEN on 22 September 2020.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 9053-2:2020 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 9053-2:2020) has been prepared by Technical Committee ISO/TC 43
"Acoustics" in collaboration with Technical Committee CEN/TC 126 “Acoustic properties of building
elements and of buildings” the secretariat of which is held by AFNOR.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by April 2021, and conflicting national standards shall be
withdrawn at the latest by April 2021.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
Endorsement notice
The text of ISO 9053-2:2020 has been approved by CEN as EN ISO 9053-2:2020 without any
modification.
INTERNATIONAL ISO
STANDARD 9053-2
First edition
2020-09
Acoustics — Determination of airflow
resistance —
Part 2:
Alternating airflow method
Acoustique — Détermination de la résistance à l’écoulement de l’air —
Partie 2: Méthode avec écoulement d’air alternatif
Reference number
ISO 9053-2:2020(E)
©
ISO 2020
ISO 9053-2:2020(E)
© 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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ii © ISO 2020 – All rights reserved

ISO 9053-2:2020(E)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3  Terms and definitions . 1
4  Symbols . 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 . 7
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 Homogeneity of test specimen . 8
7.2 Shape . 8
7.3 Dimensions . 8
7.3.1 Lateral dimensions . . 8
7.3.2 Thickness . 9
7.4 Number of test specimens . 9
8  Test procedure . 9
9 Uncertainty .10
10 Test report .11
Annex A (normative) Effective ratio of specific heats for air .12
Annex B (informative) Acoustic model of the flow .15
Annex C (informative) Calculation of uncertainty .17
Annex D (informative) Airflow resistance of perforated support .19
Bibliography .20
ISO 9053-2:2020(E)
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 first edition of ISO 9053-2, together with ISO 9053-1:2018, cancels and replaces ISO 9053:1991,
which has been technically revised.
The main changes compared to the previous edition are as follows:
— the former method B in ISO 9053:1991 has been transferred to this document;
— the requirement to the dimensions of the test specimen have been updated;
— a correction for heat conduction has been 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.
iv © ISO 2020 – All rights reserved

INTERNATIONAL STANDARD ISO 9053-2:2020(E)
Acoustics — Determination of airflow resistance —
Part 2:
Alternating airflow method
1 Scope
This document specifies an alternating airflow method for the determination of the airflow
[5], [6]
resistance 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/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in
me a s ur ement (GUM: 1995)
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:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
airflow resistance
R
quantity defined by
Dp
R=
q
v
where
Dp
is the RMS air pressure difference, across the test specimen, due to the alternating airflow,
in pascals;
q is the RMS volumetric airflow rate, passing through the test specimen, in cubic metres
v
per second.
Note 1 to entry: Airflow resistance is expressed in pascals seconds per cubic metre.
ISO 9053-2:2020(E)
3.2
specific airflow resistance
R
s
quantity defined by
RR=⋅A
s
where
R
is the airflow resistance of the test specimen, in pascals seconds per cubic metre;
A
is the cross-section area of the test specimen, perpendicular to the direction of flow, in
square metres.
Note 1 to entry: Specific airflow resistance is expressed in pascals seconds per metre.
3.3
airflow resistivity
σ
quantity defined by the following formula if the material is considered as being homogeneous
R
s
σ=
d
where
R is the specific airflow resistance of the test specimen, in pascals seconds per metre;
s
d
is the thickness of the test specimen, in the direction of flow, in metres.
Note 1 to entry: Airflow resistivity is expressed in pascals seconds per square metre.
3.4
airflow velocity
v
quantity defined by
q
v
v=
A
where
q is the RMS volumetric airflow rate, passing through the test specimen, in cubic metres per
v
second;
A
is the cross-sectional area of the test specimen, perpendicular to the direction of flow, in
square metres.
Note 1 to entry: Airflow velocity is expressed in metres per second.
2 © ISO 2020 – All rights reserved

ISO 9053-2:2020(E)
3.5
sound pressure level
L
p
ten times the logarithm to the base 10 of the ratio of the time average of the square of the sound
pressure, pt() , during a stated time interval of duration, T (starting at t and ending at t ), to the
1 2
square of a reference value, p :
t
 2 
pt()dt
 ∫ 
t
T
L =10lg dB
p
 p 
 
 
where the reference value, p , is 20 μPa
Note 1 to entry: The sound pressure level is expressed in decibels.
4  Symbols
A cross-section area of the test specimen, in square metres;
A cross sectional area of the piston, in square metres;
P
b thickness of the thermal boundary layer, in metres;
C specific heat capacity at constant pressure, in joules per kilogram and degree kelvin;
P
c speed of sound, in metres per second;
d thickness of the test specimen, in the direction of flow, in metres;
f frequency of the piston movement, in hertz;
h amplitude of the stroke of the piston, in metres;
h
amplitude of the stroke of the piston when the measurement cell with the test specimen is
s
mounted, in metres;
h amplitude of the stroke of the piston when the air cavity is closed by the airtight termina-
t
tion, in metres;
j
−1
k thermal conductivity, in joules per meter, second and degree kelvin;
a
L sound pressure level, in decibels;
p
L background sound pressure level, in decibels;
pb,
L
sound pressure level in the air cavity when the measurement cell with the test specimen is
ps,
mounted, in decibels;
L sound pressure level in the air cavity with the airtight termination, in decibels;
pt,
l characteristic thermal diffusion length, in metres;
h
N acoustic compliance, in cubic metres per pascal;
P static pressure, in pascals;
S
ISO 9053-2:2020(E)
p
sound pressure, in pascals;
p
sound pressure when the test cell with the test specimen is mounted, in pascals;
s
p sound pressure when the air cavity is closed by the airtight termination, in pascals;
t
p sound pressure reference value, 20 µPa;
q rms value of the volume flow when the test cell with the test specimen is mounted, in cubic
s
metres per second;
q rms value of the volume flow when the air cavity is closed by the airtight termination, in
t
cubic metres per second;
q rms volumetric airflow rate, passing through the test specimen, in cubic metres per second;
v
R airflow resistance of the test specimen, in pascals seconds per cubic metre;
R specific airflow resistance of the test specimen, in pascals seconds per metre;
s
r ratio between the stroke amplitudes;
r radius of the perforations in the specimen support (Annex D), in metres;
r
S total area, in square metres;
U expanded uncertainty;
u standard uncertainty;
V volume of the air cavity with the airtight termination, in cubic metres;
v airflow velocity, in metres per second;
v rms-value of the airflow velocity through the test specimen, in metres per second;
s
y thickness of the support, in metres;
Z acoustic impedance of the cavity, in pascals seconds per cubic metres;
a
Dp
rms air pressure difference, across the test specimen, due to the alternating airflow, in
pascals;
φ
perforation rate;
η dynamic viscosity of air, in pascals seconds;
κ
ratio of specific heats for air;
κ '
effective ratio of specific heats for air;
λ wavelength, in metres;
ρ density of air, in kilograms per cubic metre;
σ
airflow resistivity of the test specimen, in pascals seconds per square metre;
ω
circular frequency, 2 · π · f, in per second.
4 © ISO 2020 – All rights reserved

ISO 9053-2:2020(E)
5  Principle
An alternating volume flow with a low frequency, f , 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
that 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 is the outside atmospheric pressure modulated by the alternating flow
generated by the piston. The microphone mounted inside the cavity therefore measures 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 that can be
calculated from the piston movement, the 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 can be computed.
It can be practical to use different piston stroke lengths for the closed vessel and when the measurement
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
ISO 9053-2:2020(E)
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 a static flow can give a different result. Examples of such materials are: a) fibre materials with
large fibres, such as some metal or plant fibres, b) foams with low porosity but big pores, such as some metal
foams, c) granular materials with large grains and low porosity, such as road pavements.
6 Equipment
6.1  General
The equipment shall consist of:
a) a device for producing the alternating airflow (see 6.2);
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 (see 6.3);
c) a vessel (see 6.4)
— containing the air cavity,
— allowing connections to the microphone and the source of the alternating airflow, and
— including an airtight termination and a measurement cell;
d) a device for measuring the static pressure (see 6.5);
e) a device for measuring the frequency of the piston (see 6.6);
f) a device for measuring the thickness of the test specimen when it is positioned 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, f , shall be in the range of 1 Hz to 4 Hz and known with sufficient accuracy (see Annex C).
6 © ISO 2020 – All rights reserved

ISO 9053-2:2020(E)
The amplitude of the piston stroke, h (see Figure 1 and Figure 2), shall be determined, normally by
dimensional measurements. The rms-value of the volume flow, q , produced by the moving piston is
v
qf=⋅2 π⋅⋅hA⋅
vP
Different stroke lengths can be applied for the measurement with the airtight termination and the
measurement cell with specimen. The two lengths shall be selected to obtain suitable sound pressure
levels in both situations as well as to generate the required airflow velocity through the specimen. 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.
The rms-value of the flow velocity through the test specimen, in metres per second, is calculated
according to Formula (1):
2⋅⋅π fh⋅⋅A
sP
v = (1)
s
A
−4 -1 −−31
It is recommen
...