SIST EN ISO 11691:2021

Acoustics - Measurement of insertion loss of ducted silencers without flow - Laboratory survey method (ISO 11691:2020)

This document specifies a laboratory substitution method to determine the insertion loss without flow
of ducted, mainly absorbent, circular and rectangular silencers, as well as other duct elements for use
in ventilating and air-conditioning systems.
NOTE Laboratory measurement procedures for ducted silencers with superimposed flow are described in
ISO 7235[5].
This document is applicable to silencers where the design velocity does not exceed 15 m/s. As the
method does not include self-generated flow noise, this document is not suitable for tests on silencers
where this type of noise is of great importance for the evaluation of the silencer performance. As most
silencers, particularly in offices and dwelling, have design velocities below 15 m/s, this document can
often be a cost-efficient alternative to ISO 7235[5].
The insertion loss determined according to this document in a laboratory is not necessarily the same
as the insertion loss obtained in an installation in the field. Different sound and flow fields in the duct
yield different results. In this document, the sound field is dominated by plane wave modes. Due to the
use of regular test ducts, the results can include some flanking transmission via structural vibrations
in the duct walls that sets an upper limit to the insertion loss that can be determined.
This document is intended to be used for circular silencers with diameters of 80 mm to 2 000 mm or for
rectangular silencers with cross-sectional areas within the same range.

Akustik - Messung des Einfügungsdämpfungsmaßes von Schalldämpfern in Kanälen ohne Strömung - Laborverfahren der Genauigkeitsklasse 3 (ISO 11691:2020)

Dieses Dokument legt ein Substitutionsverfahren zur Bestimmung des Einfügungsdämpfungsmaßes unter Laborbedingungen von runden oder rechteckigen, hauptsächlich absorbierend wirkenden Kanalschall-dämpfern ohne Strömung sowie von anderen Kanalelementen zum Einsatz in raumlufttechnischen Anlagen fest.
ANMERKUNG   Labormessverfahren für Kanalschalldämpfer mit überlagerter Strömung werden in ISO 7235 [5] beschrieben.
Dieses Dokument gilt für Schalldämpfer mit einer Auslegungsgeschwindigkeit von höchstens 15 m/s. Da in diesem Dokument das Strömungsgeräusch nicht behandelt wird, eignet es sich nicht zur Anwendung auf solche Schalldämpfer, bei denen diese Art des Geräusches wesentlich für die Beurteilung der Wirkung des Schalldämpfers ist. Da die meisten Schalldämpfer, insbesondere in Büro- und Wohnräumen, niedrigere Auslegungsgeschwindigkeiten als 15 m/s aufweisen, kann dieses Dokument häufig eine wirtschaftliche Alternative zu ISO 7235 [5] darstellen.
Das nach diesem Dokument in einem Labor ermittelte Einfügungsdämpfungsmaß ist nicht notwendigerweise gleich dem Einfügungsdämpfungsmaß, das sich in einer Anlage unter Betriebsbedingungen ergibt. Unterschiedliche Schall- und Strömungsfelder im Kanal führen zu unterschiedlichen Ergebnissen. In diesem Dokument überwiegen beim Schallfeld ebene Wellenformen. Durch den Einsatz von üblichen Prüfkanälen können die Messergebnisse Beiträge durch Nebenwegübertragung von Körperschall über die Kanalwände enthalten, wodurch das bestimmbare Einfügungsdämpfungsmaß nach oben beschränkt wird.
Dieses Dokument ist vorgesehen zur Anwendung auf runde Schalldämpfer mit Durchmessern von 80 mm bis 2 000 mm und für rechteckige Schalldämpfer mit Querschnittsflächen derselben Größenordnung.

Acoustique - Détermination de la perte d'insertion de silencieux en conduit sans écoulement - Méthode de mesurage en laboratoire (ISO 11691:2020)

Specifies a laboratory substitution method to determine the insertion loss of ducted circular and rectangular silencers without flow, as well as other duct elements for use in ventilating and air-conditioning systems.

Akustika - Merjenje dodanega dušenja dušilnika zvoka v kanalu brez pretoka - Laboratorijska informativna metoda (ISO 11691:2020)

General Information

• Status: Published
• Public Enquiry End Date: 04-Jul-2019
• Publication Date: 26-Jan-2021
• ICS: 17.140.01 - Acoustic measurements and noise abatement in general
• ICS: 91.120.20 - Acoustics in building. Sound insulation
• Technical Committee: AKU - Acoustics
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 08-Dec-2020
• Due Date: 12-Feb-2021
• Completion Date: 27-Jan-2021
• Directive: 2006/42/EC - Directive 2006/42/EC of the European Parliament and of the Council of 17 May 2006 on machinery, and amending Directive 95/16/EC (recast)
• Mandate: M/396 - Mandate to CEN and Cenelec for standardisation in the field of machinery
• Mandate: M/BC/CEN/88/13 - Standardization request to CEN/CENELEC relating to machinery
• Ref Project: EN ISO 11691:2020 - Acoustics - Measurement of insertion loss of ducted silencers without flow - Laboratory survey method (ISO 11691:2020)

Relations

• Replaces: SIST EN ISO 11691:2009 - Acoustics - Measurement of insertion loss of ducted silencers without flow - Laboratory survey method (ISO 11691:1995)
• Effective Date: 01-Mar-2021
• Replaces: SIST EN ISO 11691:2009 - Acoustics - Measurement of insertion loss of ducted silencers without flow - Laboratory survey method (ISO 11691:1995)
• Effective Date: 08-Jun-2022

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN ISO 11691:2021
01-marec-2021
Nadomešča:
SIST EN ISO 11691:2009
Akustika - Merjenje dodanega dušenja dušilnika zvoka v kanalu brez pretoka -
Laboratorijska informativna metoda (ISO 11691:2020)

Acoustics - Measurement of insertion loss of ducted silencers without flow - Laboratory

survey method (ISO 11691:2020)
Akustik - Messung des Einfügungsdämpfungsmaßes von Schalldämpfern in Kanälen
ohne Strömung - Laborverfahren der Genauigkeitsklasse 3 (ISO 11691:2020)
Acoustique - Détermination de la perte d'insertion de silencieux en conduit sans
écoulement - Méthode de mesurage en laboratoire (ISO 11691:2020)
Ta slovenski standard je istoveten z: EN ISO 11691:2020
ICS:
17.140.01 Akustična merjenja in Acoustic measurements and
blaženje hrupa na splošno noise abatement in general
91.120.20 Akustika v stavbah. Zvočna Acoustics in building. Sound
izolacija insulation
SIST EN ISO 11691:2021 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 11691:2021
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SIST EN ISO 11691:2021
EN ISO 11691
EUROPEAN STANDARD
NORME EUROPÉENNE
November 2020
EUROPÄISCHE NORM
ICS 91.120.20 Supersedes EN ISO 11691:2009
English Version
Acoustics - Measurement of insertion loss of ducted
silencers without flow - Laboratory survey method (ISO
11691:2020)

Acoustique - Détermination de la perte d'insertion de Akustik - Messung des Einfügungsdämpfungsmaßes

silencieux en conduit sans écoulement - Méthode de von Schalldämpfern in Kanälen ohne Strömung -

contôle en laboratoire (ISO 11691:2020) Laborverfahren der Genauigkeitsklasse 3 (ISO

11691:2020)
This European Standard was approved by CEN on 22 July 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 11691:2020 E

worldwide for CEN national Members.
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SIST EN ISO 11691:2021
EN ISO 11691:2020 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST EN ISO 11691:2021
EN ISO 11691:2020 (E)
European foreword

This document (EN ISO 11691:2020) has been prepared by Technical Committee ISO/TC 43 "Acoustics"

in collaboration with Technical Committee CEN/TC 211 “Acoustics” the secretariat of which is held by

DIN.

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 May 2021, and conflicting national standards shall be

withdrawn at the latest by May 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.

This document supersedes EN ISO 11691:2009.

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 11691:2020 has been approved by CEN as EN ISO 11691:2020 without any modification.

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SIST EN ISO 11691:2021
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SIST EN ISO 11691:2021
INTERNATIONAL ISO
STANDARD 11691
Second edition
2020-07
Acoustics — Measurement of insertion
loss of ducted silencers without flow
— Laboratory survey method
Acoustique — Détermination de la perte d'insertion de silencieux en
conduit sans écoulement — Méthode de contôle en laboratoire
Reference number
ISO 11691:2020(E)
ISO 2020
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SIST EN ISO 11691:2021
ISO 11691:2020(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: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved
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SIST EN ISO 11691:2021
ISO 11691:2020(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Test facility and arrangement ................................................................................................................................................................. 2

4.1 General ........................................................................................................................................................................................................... 2

4.2 Sound measuring equipment ..................................................................................................................................................... 3

4.3 Sound source equipment ............................................................................................................................................................... 4

4.3.1 General...................................................................................................................................................................................... 4

4.3.2 Electronic equipment, loudspeaker unit and transition element .......................................... 4

4.3.3 Modal filter ............................................................................................................................................................................ 4

4.4 Transition element .............................................................................................................................................................................. 5

4.5 Test ducts and substitution duct.............................................................................................................................................. 5

4.6 Reverberation room ........................................................................................................................................................................... 5

4.7 Other measurement environments ....................................................................................................................................... 5

5 Test procedure ........................................................................................................................................................................................................ 5

6 Measurement uncertainty .......................................................................................................................................................................... 6

7 Information to be recorded ....................................................................................................................................................................... 6

7.1 General ........................................................................................................................................................................................................... 6

7.2 Description of the silencer under test................................................................................................................................. 6

7.3 Description of the test arrangement .................................................................................................................................... 7

7.4 Acoustical test result .......................................................................................................................................................................... 7

8 Information to be reported ....................................................................................................................................................................... 7

Bibliography ................................................................................................................................................................................................................................ 8

© ISO 2020 – All rights reserved iii
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SIST EN ISO 11691:2021
ISO 11691:2020(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 1, Noise.

This second edition cancels and replaces the first edition (ISO 11691:1995), which has been technically

revised. The main changes compared to the previous edition are as follows:

— a modal filter has been inserted after the source to bring the standard more in line with the

[5]
corresponding arrangements in ISO 7235:2003 , and

— in this edition, test ducts and test object should, if possible, have the same cross-sections.

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 11691:2021
ISO 11691:2020(E)
Introduction

The insertion loss of absorbent silencers is generally not affected by the air flow, provided that the

flow velocity does not exceed approximately 20 m/s in the narrowest cross-section of the silencer. In

practice, non-uniform flow distributions must be considered, therefore the limit velocity of 20 m/s

corresponds to a design velocity of 10 m/s to 15 m/s.
© ISO 2020 – All rights reserved v
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SIST EN ISO 11691:2021
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SIST EN ISO 11691:2021
INTERNATIONAL STANDARD ISO 11691:2020(E)
Acoustics — Measurement of insertion loss of ducted
silencers without flow — Laboratory survey method
1 Scope

This document specifies a laboratory substitution method to determine the insertion loss without flow

of ducted, mainly absorbent, circular and rectangular silencers, as well as other duct elements for use

in ventilating and air-conditioning systems.

NOTE Laboratory measurement procedures for ducted silencers with superimposed flow are described in

[5]
ISO 7235 .

This document is applicable to silencers where the design velocity does not exceed 15 m/s. As the

method does not include self-generated flow noise, this document is not suitable for tests on silencers

where this type of noise is of great importance for the evaluation of the silencer performance. As most

silencers, particularly in offices and dwelling, have design velocities below 15 m/s, this document can

[5]
often be a cost-efficient alternative to ISO 7235 .

The insertion loss determined according to this document in a laboratory is not necessarily the same

as the insertion loss obtained in an installation in the field. Different sound and flow fields in the duct

yield different results. In this document, the sound field is dominated by plane wave modes. Due to the

use of regular test ducts, the results can include some flanking transmission via structural vibrations

in the duct walls that sets an upper limit to the insertion loss that can be determined.

This document is intended to be used for circular silencers with diameters of 80 mm to 2 000 mm or for

rectangular silencers with cross-sectional areas within the same range.
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 3741, Acoustics — Determination of sound power
...