SIST EN ISO 9053-2:2020
(Main)Acoustics - Determination of airflow resistance - Part 2: Alternating airflow method (ISO 9053-2:2020)
Acoustics - Determination of airflow resistance - Part 2: Alternating airflow method (ISO 9053-2:2020)
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.
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 upora pretoku zraka - 2. del: Metoda izmeničnega pretoka zraka (ISO 9053-2:2020)
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 9053-2:2020
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
SIST EN ISO 9053-2:2020 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 9053-2:2020
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SIST EN ISO 9053-2:2020
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.
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SIST EN ISO 9053-2:2020
EN ISO 9053-2:2020 (E)
Contents Page
European foreword . 3
2
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SIST EN ISO 9053-2:2020
EN ISO 9053-2:2020 (E)
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.
3
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SIST EN ISO 9053-2:2020
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SIST EN ISO 9053-2:2020
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
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SIST EN ISO 9053-2:2020
ISO 9053-2:2020(E)
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
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: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved
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SIST EN ISO 9053-2:2020
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 2020 – All rights reserved iii
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SIST EN ISO 9053-2:2020
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
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SIST EN ISO 9053-2:2020
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.
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SIST EN ISO 9053-2:2020
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
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SIST EN ISO 9053-2:2020
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 :
0
t
1
2
2
pt()dt
∫
t
T
1
L =10lg dB
p
2
p
0
where the reference value, p , is 20 μPa
0
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;
0
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
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SIST EN ISO 9053-2:2020
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;
0
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;
0
σ
airflow resistivity of the test specimen, in pascals seconds per square metre;
ω
circular frequency, 2 · π · f, in per second.
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SIST EN ISO 9053-2:2020
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
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SIST EN ISO 9053-2:2020
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
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SIST EN ISO 9053-2:2020
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 recommended to use rms-values of the flow velocity between 51· 0 ms and 41· 0 ms .
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 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 pressures 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.
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.
It is important that the sound measuring device only measure 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.
NOTE 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.
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, V , of the air cavity inside the closed vessel with the
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SIST EN ISO 9053-2:2020
ISO 9053-2:2020(E)
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 that 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 document.
The vessel and the measurement cell should be made so 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 Annex D for additional 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. Th
...
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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oSIST prEN ISO 9053-2:2020
ISO/DIS 9053-2:2020(E)
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
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: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved
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oSIST prEN ISO 9053-2:2020
ISO/DIS 9053-2:2019(E)
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
...
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