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

Status
Published
Public Enquiry End Date
19-Mar-2020
Publication Date
15-Nov-2020
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
19-Oct-2020
Due Date
24-Dec-2020
Completion Date
16-Nov-2020

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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

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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.
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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
quantity defined by
where

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

per second.

Note 1 to entry: Airflow resistance is expressed in pascals seconds per cubic metre.

© ISO 2020 – All rights reserved 1
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SIST EN ISO 9053-2:2020
ISO 9053-2:2020(E)
3.2
specific airflow resistance
quantity defined by
RR=⋅A
where

is the airflow resistance of the test specimen, in pascals seconds per cubic metre;

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

quantity defined by the following formula if the material is considered as being homogeneous

where

R is the specific airflow resistance of the test specimen, in pascals seconds per metre;

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
quantity defined by
where

q is the RMS volumetric airflow rate, passing through the test specimen, in cubic metres per

second;

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

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 :
 2 
pt()dt
 ∫ 
L =10lg dB
 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;
b thickness of the thermal boundary layer, in metres;

C specific heat capacity at constant pressure, in joules per kilogram and degree kelvin;

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;

amplitude of the stroke of the piston when the measurement cell with the test specimen is

mounted, in metres;

h amplitude of the stroke of the piston when the air cavity is closed by the airtight termina-

tion, in metres;
k thermal conductivity, in joules per meter, second and degree kelvin;
L sound pressure level, in decibels;
L background sound pressure level, in decibels;
pb,

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;
N acoustic compliance, in cubic metres per pascal;
P static pressure, in pascals;
© ISO 2020 – All rights reserved 3
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SIST EN ISO 9053-2:2020
ISO 9053-2:2020(E)
sound pressure, in pascals;
sound pressure when the test cell with the test specimen is mounted, in pascals;

p sound pressure when the air cavity is closed by the airtight termination, in pascals;

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

metres per second;

q rms value of the volume flow when the air cavity is closed by the airtight termination, in

cubic metres per second;

q rms volumetric airflow rate, passing through the test specimen, in cubic metres per second;

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;

r ratio between the stroke amplitudes;
r radius of the perforations in the specimen support (Annex D), in metres;
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;

y thickness of the support, in metres;
Z acoustic impedance of the cavity, in pascals seconds per cubic metres;

rms air pressure difference, across the test specimen, due to the alternating airflow, in

pascals;
perforation rate;
η dynamic viscosity of air, in pascals seconds;
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;
airflow resistivity of the test specimen, in pascals seconds per square metre;
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

qf=⋅2 π⋅⋅hA⋅

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
v = (1)
−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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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
...

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