IEC 61400-11:2002

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
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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
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– 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
...