IEC 61400-11:2002

Wind turbine generator systems - Part 11: Acoustic noise measurement techniques

Presents measurement procedures that enable noise emissions of a wind tubine to be characterized with respect to a range of wind speeds and directions. Allows comparisons between different wind turbines. May be applied by wind turbine manufacturers, purchasers, operators and planners or regulators.
This publication is of high relevance for Smart Grid.

General Information

• Status: Published
• Publication Date: 27-Nov-2006
• ICS: 27.180 - Wind turbine energy systems
• Technical Committee: TC 88 - Wind energy generation systems
• Drafting Committee: MT 11 - TC 88/MT 11
• Current Stage: DELPUB - Deleted Publication
• Completion Date: 07-Nov-2012

Relations

• Amended By: IEC 61400-11:2002/AMD1:2006 - Amendment 1 - Wind turbine generator systems - Part 11: Acoustic noise measurement techniques
• Effective Date: 05-Sep-2023
• Revised: IEC 61400-11:2012 - Wind turbines - Part 11: Acoustic noise measurement techniques
• Effective Date: 05-Sep-2023
• Revises: IEC 61400-11:1998 - Wind turbine generator systems - Part 11: Acoustic noise measurement techniques
• Effective Date: 05-Sep-2023

Standards Content (Sample)

INTERNATIONAL IEC
STANDARD
61400-11
Second edition
2002-12
Wind turbine generator systems –
Part 11:
Acoustic noise measurement techniques
Aérogénérateurs –
Partie 11:
Techniques de mesure du bruit acoustique
Reference number
Publication numbering
As from 1 January 1997 all IEC publications are issued with a designation in the
60000 series. For example, IEC 34-1 is now referred to as IEC 60034-1.
Consolidated editions
The IEC is now publishing consolidated versions of its publications. For example,
edition numbers 1.0, 1.1 and 1.2 refer, respectively, to the base publication, the
base publication incorporating amendment 1 and the base publication incorporating
amendments 1 and 2.
Further information on IEC publications
The technical content of IEC publications is kept under constant review by the IEC,
thus ensuring that the content reflects current technology. Information relating to
this publication, including its validity, is available in the IEC Catalogue of
publications (see below) in addition to new editions, amendments and corrigenda.
Information on the subjects under consideration and work in progress undertaken
by the technical committee which has prepared this publication, as well as the list
of publications issued, is also available from the following:
• IEC Web Site (www.iec.ch)
• Catalogue of IEC publications
The on-line catalogue on the IEC web site (http://www.iec.ch/searchpub/cur_fut.htm)
enables you to search by a variety of criteria including text searches, technical
committees and date of publication. On-line information is also available on
recently issued publications, withdrawn and replaced publications, as well as
corrigenda.
• IEC Just Published
This summary of recently issued publications (http://www.iec.ch/online_news/
justpub/jp_entry.htm) is also available by email. Please contact the Customer
Service Centre (see below) for further information.
• Customer Service Centre
If you have any questions regarding this publication or need further assistance,
please contact the Customer Service Centre:
Email: [e-mail]
Tel: [phone]
Fax: [phone]
INTERNATIONAL IEC
STANDARD
61400-11
Second edition
2002-12
Wind turbine generator systems –
Part 11:
Acoustic noise measurement techniques
Aérogénérateurs –
Partie 11:
Techniques de mesure du bruit acoustique
 IEC 2002  Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic or
mechanical, including photocopying and microfilm, without permission in writing from the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: [phone] Telefax: [phone] E-mail: [e-mail]  Web: www.iec.ch
PRICE CODE
Commission Electrotechnique Internationale
X
International Electrotechnical Commission
Международная Электротехническая Комиссия
For price, see current catalogue

– 2 – 61400-11  IEC:2002(E)
CONTENTS
FOREWORD . 4
INTRODUCTION .5
1 Scope . 6
2 Normative references. 6
3 Definitions . 7
4 Symbols and units . 8
5 Outline of method . 9
6 Instrumentation.10
6.1 Acoustic instruments.10
6.2 Non-acoustic Instruments .11
6.3 Traceable calibration .12
7 Measurements and measurement procedures .12
7.1 Measurement positions.12
7.2 Acoustic measurements.13
7.3 Non-acoustic measurements.15
8 Data reduction procedures.17
8.1 Wind speed .17
8.2 Correction for background noise .18
8.3 Apparent sound power levels.18
8.4 One-third octave band levels .19
8.5 Tonality .19
8.6 Directivity (optional).22
9 Information to be reported.23
9.1 Characterisation of the wind turbine.23
9.2 Physical environment.24
9.3 Instrumentation.24
9.4 Acoustic data.24
9.5 Non-acoustic data.25
9.6 Uncertainty .25
Annex A (informative) Other possible characteristics of wind turbine noise emission
and their quantification.35
Annex B (informative) Criteria for recording/playback equipment.37
Annex C (Informative) Assessment of turbulence intensity .39
Annex D (informative) Assessment of measurement uncertainty.40
Bibliography.43
Figure 1 – Mounting of the microphone .26
Figure 2 − Picture of microphone and board .27
Figure 3 − Standard pattern for microphone measurement positions (plan view).28
Figure 4 − Illustration of the definitions of R and slant distance R .29
0 1
61400-11  IEC:2002(E) – 3 –
Figure 5 − Allowable region for meteorological mast position as a function of β –
plan view.30
Figure 6 − Allowable range for anemometer height – cross section .31
Figure 7 – Workflow chart for tonality procedure .32
Figure 8 – Illustration of L level in the critical band .33
70 %
Figure 9 – Illustration of lines below the L + 6dB criterion .33
70 %
Figure 10 – Illustration of L level and lines classified as masking.34
pn,avg
Figure 11 – Illustration of classifying all spectral lines .34
Figure B.1 − Tolerances for frequency characteristic, IEC 60651 type 1 .37
Table 1 − Roughness length.18
Table 2 − Frequency resolution .19
Table D.1 − Examples of possible values of type B uncertainty components relevant for
apparent sound power level .41

– 4 – 61400-11  IEC:2002(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
WIND TURBINE GENERATOR SYSTEMS –
Part 11: Acoustic noise measurement techniques
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, the IEC publishes International Standards. Their preparation is
entrusted to technical committees; any IEC National Committee interested in the subject dealt with may
participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. The IEC collaborates closely with the International
Organization for Standardization (ISO) in accordance with conditions determined by agreement between the
two organizations.
2) The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, an
international consensus of opinion on the relevant subjects since each technical committee has representation
from all interested National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical specifications, technical reports or guides and they are accepted by the National
Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61400-11 has been prepared by IEC technical committee 88: Wind
turbine systems.
This second edition of IEC 61400-11 cancels and replaces the first edition published in 1998
and constitutes a technical revision.
The text of this standard is based on the following documents:
FDIS Report on voting
88/166/FDIS 88/171/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this publication will remain unchanged
until 2004. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
61400-11  IEC:2002(E) – 5 –
INTRODUCTION
The purpose of this part of IEC 61400 is to provide a uniform methodology that will ensure
consistency and accuracy in the measurement and analysis of acoustical emissions by wind
turbine generator systems. The standard has been prepared with the anticipation that it would
be applied by:
• the wind turbine manufacturer striving to meet well defined acoustic emission performance
requirements and/or a possible declaration system;
• the wind turbine purchaser in specifying such performance requirements;
• the wind turbine operator who may be required to verify that stated, or required, acoustic
performance specifications are met for new or refurbished units;
• the wind turbine planner or regulator who must be able to accurately and fairly define
acoustical emission characteristics of a wind turbine in response to environmental
regulations or permit requirements for new or modified installations.
This standard provides guidance in the measurement, analysis and reporting of complex
acoustic emissions from wind turbine generator systems. The standard will benefit those
parties involved in the manufacture, installation, planning and permitting, operation,
utilization, and regulation of wind turbines. The measurement and analysis techniques
recommended in this document should be applied by all parties to insure that continuing
development and operation of wind turbines is carried out in an atmosphere of consistent and
accurate communication relative to environmental concerns. This standard presents
measurement and reporting procedures expected to provide accurate results that can be
replicated by others.
– 6 – 61400-11  IEC:2002(E)
WIND TURBINE GENERATOR SYSTEMS –
Part 11: Acoustic noise measurement techniques
1 Scope
This part of IEC 61400 presents measurement procedures that enable noise emissions of a
wind turbine to be characterised. This involves using measurement methods appropriate to
noise emission assessment at locations close to the machine, in order to avoid errors due to
sound propagation, but far enough away to allow for the finite source size. The procedures
described are different in some respects from those that would be adopted for noise
assessment in community noise studies. They
...

IEC 61400-11
Edition 2.1 2006-11
INTERNATIONAL
STANDARD
Wind turbine generator systems –
Part 11: Acoustic noise measurement techniques

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester.
If you have any questions about IEC copyright or have an enquiry about obtaining additional rights to this publication,
please contact the address below or your local IEC member National Committee for further information.

IEC Central Office
3, rue de Varembé
CH-1211 Geneva 20
Switzerland
Email: [e-mail]
Web: www.iec.ch
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.
ƒ Catalogue of IEC publications: www.iec.ch/searchpub
The IEC on-line Catalogue enables you to search by a variety of criteria (reference number, text, technical committee,…).
It also gives information on projects, withdrawn and replaced publications.
ƒ IEC Just Published: www.iec.ch/online_news/justpub
Stay up to date on all new IEC publications. Just Published details twice a month all new publications released. Available
on-line and also by email.
ƒ Electropedia: www.electropedia.org
The world's leading online dictionary of electronic and electrical terms containing more than 20 000 terms and definitions
in English and French, with equivalent terms in additional languages. Also known as the International Electrotechnical
Vocabulary online.
ƒ Customer Service Centre: www.iec.ch/webstore/custserv
If you wish to give us your feedback on this publication or need further assistance, please visit the Customer Service
Centre FAQ or contact us:
Email: [e-mail]
Tel.: [phone]
Fax: [phone]
IEC 61400-11
Edition 2.1 2006-11
INTERNATIONAL
STANDARD
Wind turbine generator systems –
Part 11: Acoustic noise measurement techniques

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
CN
ICS 27.180 ISBN 2-8318-8692-9
– 2 – 61400-11 © IEC:2002+A1:2006(E)
CONTENTS
FOREWORD.4
INTRODUCTION.6

1 Scope.7
2 Normative references.7
3 Definitions.8
4 Symbols and units .9
5 Outline of method.10
6 Instrumentation.11
6.1 Acoustic instruments.11
6.2 Non-acoustic Instruments.13
6.3 Traceable calibration.13
7 Measurements and measurement procedures.14
7.1 Measurement positions.14
7.2 Acoustic measurements .15
7.3 Non-acoustic measurements.17
8 Data reduction procedures.20
8.1 Wind speed.20
8.2 Correction for background noise.21
8.3 Apparent sound power levels.21
8.4 One-third octave band levels .22
8.5 Tonality.22
8.6 Directivity (optional).25
9 Information to be reported .25
9.1 Characterisation of the wind turbine .26
9.2 Physical environment.27
9.3 Instrumentation.27
9.4 Acoustic data .27
9.5 Non-acoustic data.28
9.6 Uncertainty.28

Annex A (informative) Other possible characteristics of wind turbine noise emission
and their quantification .38
Annex B (informative) Criteria for recording/playback equipment .40
Annex C (Informative) Assessment of turbulence intensity .42
Annex D (informative) Assessment of measurement uncertainty .43

Bibliography.46

Figure 1 – Mounting of the microphone .29
Figure 2 − Picture of microphone and board.30
Figure 3 − Standard pattern for microphone measurement positions (plan view) .31
Figure 4 − Illustration of the definitions of R and slant distance R .32
0 1
61400-11 © IEC:2002+A1:2006(E) – 3 –
Figure 5 − Allowable region for meteorological mast position as a function of β –
plan view .33
Figure 6 − Allowable range for anemometer height – cross section .34
Figure 7 – Workflow chart for tonality procedure .35
Figure 8 – Illustration of L level in the critical band .36
70 %
Figure 9 – Illustration of lines below the L + 6dB criterion.36
70 %
Figure 10 – Illustration of L level and lines classified as masking .37
pn,avg
Figure 11 – Illustration of classifying all spectral lines.37
Figure B.1 − Tolerances for frequency characteristic, IEC 60651 type 1.40

Table 1 − Roughness length.20
Table 2 − Frequency resolution .22
Table D.1 − Examples of possible values of type B uncertainty components relevant for
apparent sound power level .44

– 4 – 61400-11 © IEC:2002+A1:2006(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
WIND TURBINE GENERATOR SYSTEMS –

Part 11: Acoustic noise measurement techniques

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 61400-11 has been prepared by IEC technical committee 88: Wind
turbines.
This consolidated version of IEC 61400-11 consists of the second edition (2002) [documents
88/166/FDIS and 88/171/RVD] and its amendment 1 (2006) [documents 88/260/FDIS and
88/264/RVD].
The technical content is therefore identical to the base edition and its amendment and has
been prepared for user convenience.
It bears the edition number 2.1.
A vertical line in the margin shows where the base publication has been modified by
amendment 1.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

61400-11 © IEC:2002+A1:2006(E) – 5 –
The committee has decided that the contents of the base publication and its amendments will
remain unchanged until the maintenance result date indicated on the IEC web site under
"http://webstore.iec.ch" in the data related to the specific publication. At this date,
the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
– 6 – 61400-11 © IEC:2002+A1:2006(E)
INTRODUCTION
The purpose of this part of IEC 61400 is to provide a uniform methodology that will ensure
consistency and accuracy in the measurement and analysis of acoustical emissions by wind
turbine generator systems. The standard has been prepared with the anticipation that it would
be applied by:
• the wind turbine manufacturer striving to meet well defined acoustic emission performance
requirements and/or a possible declaration system;
• the wind turbine purchaser in specifying such performance requirements;
• the wind turbine operator who may be required to verify that stated, or required, acoustic
performance specifications are met for new or refurbished units;
• the wind turbine planner or regulator who must be able to accurately and fairly define
acoustical emission characteristics of a wind turbine in response to environmental
regulations or permit requirements for new or modified installations.
This standard provides guidance in the measurement, analysis and reporting of complex
acoustic emissions from wind turbine generator systems. The standard will benefit those
parties involved in the manufacture, installation, planning and permitting, operation,
utilization, and regulation of wind turbines. The measurement and anal
...