SIST EN 61400-11:2003
(Main)Wind turbine generator systems -- Part 11: Acoustic noise measurement techniques
Wind turbine generator systems -- Part 11: Acoustic noise measurement techniques
Presents measurement procedures that enable noise emissions of a wind turbine 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 of regulators.
Windenergieanlagen -- Teil 11: Schallmessverfahren
Aérogénérateurs -- Partie 11: Techniques de mesure du bruit acoustique
Cette norem existe seulement en langue anglaise.
Sistemi generatorjev vetrne turbine – 11. del: Tehnike merjenja hrupa (IEC 61400-11:2002)
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Standards Content (Sample)
SLOVENSKI SIST EN 61400-11:2003
STANDARD
oktober 2003
Sistemi generatorjev vetrne turbine – 11. del: Tehnike merjenja hrupa (IEC
61400-11:2002)
Wind turbine generator systems - Part 11: Acoustic noise measurement techniques
ICS 17.140.20; 27.180 Referenčna številka
SIST EN 61400-11:2003(en)
© Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno
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EUROPEAN STANDARD EN 61400-11
NORME EUROPÉENNE
EUROPÄISCHE NORM May 2003
ICS 27.180 Supersedes EN 61400-11:1998
English version
Wind turbine generator systems
Part 11: Acoustic noise measurement techniques
(IEC 61400-11:2002)
Aérogénérateurs Windenergieanlagen
Partie 11: Techniques de mesure Teil 11: Schallmessverfahren
du bruit acoustique (IEC 61400-11:2002)
(CEI 61400-11:2002)
This European Standard was approved by CENELEC on 2003-03-18. CENELEC 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 Central Secretariat or to any CENELEC 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 CENELEC member into its own language and
notified to the Central Secretariat has the same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Czech Republic,
Denmark, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Luxembourg, Malta,
Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and United Kingdom.
CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels
© 2003 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 61400-11:2003 E
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EN 61400-11:2003 - 2 -
Foreword
The text of document 88/166/FDIS, future edition 2 of IEC 61400-11, prepared by IEC TC 88, Wind
turbines, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as
EN 61400-11 on 2003-03-18.
This European Standard supersedes EN 61400-11:1998.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2003-12-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) -
Annexes designated "normative" are part of the body of the standard.
Annexes designated "informative" are given for information only.
In this standard, annex ZA is normative and annexes A to D are informative.
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 61400-11:2002 was approved by CENELEC as a European
Standard without any modification.
__________
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- 3 - EN 61400-11:2003
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
This European Standard incorporates by dated or undated reference, provisions from other
publications. These normative references are cited at the appropriate places in the text and the
publications are listed hereafter. For dated references, subsequent amendments to or revisions of any
of these publications apply to this European Standard only when incorporated in it by amendment or
revision. For undated references the latest edition of the publication referred to applies (including
amendments).
NOTE When an international publication has been modified by common modifications, indicated by (mod), the relevant
EN/HD applies.
Publication Year Title EN/HD Year
IEC 60386 1972 Method of measurement of speed - -
fluctuations in sound recording and
reproducing equipment
IEC 60651 1979 Sound level meters EN 60651 1994
IEC 60688 1992 Electrical measuring transducers for EN 60688 1992
converting a.c. electrical quantities to
analogue or digital signals
IEC 60804 2000 Integrating-averaging sound level EN 60804 2000
meters
1)
IEC 60942 1997 Electroacoustics - Sound calibrators EN 60942 1998
IEC 61260 1995 Electroacoustics - Octave-band and EN 61260 1995
fractional-octave-band filters
IEC 61400-12 1998 Wind turbine generator systems EN 61400-12 1998
Part 12: Wind turbine power
performance testing
1)
EN 60942 is superseded by EN 60942:2003, which is based on IEC 60942:2003.
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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
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: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch
PRICE CODE
Commission Electrotechnique Internationale
X
International Electrotechnical Commission
Международная Электротехническая Комиссия
For price, see current catalogue
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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
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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
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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.
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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.
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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 are intended to facilitate characterisation of
wind turbine noise with respect to a range of wind speeds and directions. Standardisation of
measurement procedures will also facilitate comparisons between different wind turbines.
The procedures present methodologies that will enable the noise emissions of a single wind
turbine to be characterised in a consistent and accurate manner. These procedures include
the following:
• location of acoustic measurement positions;
• requirements for the acquisition of acoustic, meteorological, and associated wind turbine
operational data;
• analysis of the data obtained and the content for the data report; and
• definition of specific acoustic emission parameters, and associated descriptors which are
used for making environmental assessments.
The standard is not restricted to wind turbines of a particular size or type. The procedures
described in this standard allow for the thorough description of the noise emission from a wind
turbine. If, in some cases, less comprehensive measurements are needed, such measure-
ments are made according to the relevant parts of this standard.
2 Normative references
The following referenced documents are indispensable for the application 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.
IEC 60386:1972, Method of measurement of speed fluctuations in sound recording and
reproducing equipment
IEC 60651:1979, Sound level meters
IEC 60688:1992, Electrical measuring transducers for converting a.c. electrical quantities to
analogue or digital signals
IEC 60804:2000, Integrating-averaging sound level meters
IEC 60942:1997, Electroacoustics – Sound calibrators
IEC 61260:1995, Electroacoustics – Octave-band and fractional-octave-band filters
IEC 61400-12:1998, Wind turbine generator systems – Part 12: Wind turbine power
performance testing
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61400-11 IEC:2002(E) – 7 –
3 Definitions
For the purposes of this standard, the following definitions apply:
3.1
apparent sound power level
L (in dB re. 1 pW)
WA
the A-weighted sound power level re. 1 pW of a point source at the rotor centre with the same
emission in the downwind direction as the wind turbine being measured, L is determined at
WA
each wind speed integer from 6 to 10 m/s
3.2
audibility criterion
L (in dB re. 20 µPa)
a
a frequency dependent criterion curve determined from listening tests, and reflecting the
subjective response of a ‘typical’ listener to tones of different frequencies
3.3
A-weighted or C-weighted sound pressure levels
L or L , respectively (in dB re. 20 µPa)
A C
sound pressure levels measured with the A or C frequency weighting networks specified in
IEC 60651
3.4
directivity
ΔΔΔΔ (in dB)
i
the difference between the A-weighted sound pressure levels measured at measurement
positions 2, 3, and 4 and those measured at the reference position 1 from the turbine
corrected to the same distance from the wind turbine rotor centre
3.5
inclination angle
φφ (in °)
φφ
the angle between the plane of the microphone board and a line from the microphone to the
rotor centre
3.6
reference distance
R (in m)
0
the nominal horizontal distance from the centre of the base of the wind turbine to each of the
prescribed microphone positions
3.7
reference height
z (in m)
ref
a height of 10 m used for converting wind speed to reference conditions
3.8
reference roughness length
z (in m)
0ref
a roughness length of 0,05 m used for converting wind speed to reference conditions
3.9
sound pressure level
L (in dB re. 20 µPa)
p
10 times the log of the ratio of the mean-square sound pressure to the square of the
10
reference sound pressure of 20 µPa
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– 8 – 61400-11 IEC:2002(E)
3.10
standardized wind speed
−1
V (in ms )
s
wind speed converted to reference conditions (height 10 m and roughness length 0,05 m)
using a logarithmic profile
3.11
tonal audibility ΔΔΔΔL (in dB)
a,k
The difference between the tonality and the audibility criterion at integer wind speeds k = 6, 7,
8, 9, 10
3.12
tonality ΔΔΔΔL (in dB)
k
the difference between the tone level and the level of the masking noise in the critical band
around the tone at integer wind speeds k = 6, 7, 8, 9, 10
4 Symbols and units
D rotor diameter (horizontal axis turbine) or equatorial diameter (vertical
axis turbine) (m)
H height of rotor centre (horizontal axis turbine) or height of rotor equatorial
plane (vertical axis turbine) above local ground near the wind turbine (m)
L or L A or C-weighted sound pressure level (dB)
A C
L equivalent continuous A-weighted sound pressure level at each integer
Aeq,k
wind speed, where k = 6, 7, 8, 9, 10 (dB)
L equivalent continuous A-weighted sound pressure level corrected for
Aeq,c,k
background noise at each integer wind speed and corrected to reference
conditions, where k = 6, 7, 8, 9, 10 (dB)
L equivalent continuous A-weighted sound pressure level in position ‘i ’
Aeq,i
corrected for background noise where i = 1, 2, 3, or 4 (dB)
L equivalent continuous sound pressure level of the background noise (dB)
n
th
L sound pressure level of masking noise within a critical band in the ‘j ’
pn,j,k
th
spectra at the ‘k ’ wind speed, where j = 1 to 12 and k = 6, 7, 8, 9, 10 (dB)
L average of analysis bandwidth sound pressure levels of masking in the
pn,avg,j,k
th th
‘j ’ spectra at the ‘k ’ wind speed, where j = 1 to 12 and k = 6, 7, 8, 9,
10 (dB)
th th
L sound pressure level of the tone or tones in the ‘j ’ spectra at the ‘k ’
pt,j,k
wind speed, where j = 1 to 12 and k = 6, 7, 8, 9, 10 (dB)
L equivalent continuous sound pressure level of only wind turbine noise (dB)
s
L equivalent continuous sound pressure level of combined wind turbine and
s+n
background noise (dB)
L apparent sound power level, where k = 6, 7, 8, 9, 10 (dB)
WA,k
P measured electric power (W)
m
P normalised electric power (W)
n
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61400-11 IEC:2002(E) – 9 –
R slant distance, from rotor centre to actual measurement position ‘i’,
i
where i = 1, 2, 3, or 4 (m)
R reference distance (m)
0
2 2
S reference area, S = 1 m (m )
0 0
T air temperature (C)
C
T air temperature (K)
K
U , U uncertainty components (dB)
A B
V wind speed at hub height, H (m/s)
H
V derived wind speed from power curve (m/s)
D
V wind speed at height, z (m/s)
z
V standardized wind speed (m/s)
s
f frequency of the tone (Hz)
f centre frequency of critical band (Hz)
c
p atmospheric pressure (kPa)
z roughness length (m)
0
z reference roughness length, 0,05 m (m)
0ref
z anemometer height (m)
z reference height for wind speed, 10 m (m)
ref
β angle used to define allowable area for anemometer mast location (°)
κ the ratio of standardised wind speed and measured wind speed
th
Δ directivity at ‘i ’ position, where i = 2, 3, or 4 (dB)
i
th th
Δ tonality of the ‘j ’ spectra at ‘k ’ wind speed, where j = 1 to 12 and
Ltn,j,k
k = 6, 7, 8, 9, 10 (dB)
φ inclination angle (°)
5 Outline of method
This Part of IEC 61400 defines the procedures to be used in the measurement, analysis and
reporting of acoustic emissions of a wind turbine. Instrumentation and calibration
requirements are specified to ensure accuracy and consistency of acoustic and non-acoustic
measurements. Non-acoustic measurements required defining the atmospheric conditions
relevant to determining the acoustic emissions are also specified. All parameters to be
measured and reported are identified, as are the data reduction methods required for
obtaining these parameters.
Application of the method described in this International Standard provides the apparent A-
weighted sound power levels, spectra, and tonality at integer wind speeds from 6 to 10 m/s of
an individual wind turbine. Optionally, directivity may also be determined.
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The measurements are made at locations close to the turbine in order to minimise the
influence of terrain effects, atmospheric conditions or wind-induced noise. To account for the
size of the wind turbine under test, a reference distance R based on the wind turbine
o
dimensions is used.
Measurements are taken with a microphone positioned on a board placed on the ground to
reduce the wind noise generated at the microphone and to minimise the influence of different
ground types.
Measurements of sound pressure levels and wind speeds are made simultaneously over short
periods of time and over a wide range of wind speeds. The measured wind speeds are
converted to corresponding wind speeds at a reference height of 10 m and a reference
roughness length of 0,05 m. The sound levels at standardized wind speeds of 6, 7, 8, 9, and
10 m/s are determined and used for calculating the apparent A-weighted sound power levels.
The directivity is determined by comparing the A-weighted sound pressure levels at three
additional positions around the turbine with those measured at the reference position.
Informative annexes are included that cover
• other possible characteristics of wind turbine noise emission and their quantification
(Annex A);
• criteria for recording/playback equipment (Annex B);
• assessment of turbulence intensity (Annex C);
• assessment of measurement uncertainty (Annex D).
6 Instrumentation
6.1 Acoustic instruments
The following equipment is necessary to perform the acoustic measurements as set forth in
this standard.
6.1.1 Equipment for the determination of the equivalent continuous A-weighted
sound pressure level
The equipment shall meet the requirements of a type 1 sound level meter according to
IEC 60804. The diameter of the microphone shall be no greater than 13 mm.
6.1.2 Equipment for the determination of one-third octave band spectra
In addition to the requirements given for type 1 sound level meters, the equipment shall have
a constant frequency response over at least the 45 Hz to 11 200 Hz frequency range. The
filters shall meet the requirements of IEC 61260 for Class 1 filters.
The equivalent continuous sound pressure levels in one-third octave bands shall be
determined simultaneously with centre frequencies from 50 Hz to 10 kHz. It may be relevant
to measure the low-frequency noise emission of a wind turbine. In such cases, a wider
frequency range is necessary as discussed in Annex A.
6.1.3 Equipment for the determination of narrow band spectra
The equipment shall fulfil the relevant requirements for IEC 60651 type 1 instrumentation in
the 20 Hz to 11 200 Hz frequency range.
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61400-11 IEC:2002(E) – 11 –
6.1.4 Microphone with measurement board and windscreen
The microphone shall be mounted at the centre on a flat hard board with the diaphragm of the
microphone in a plane normal to the board and with the axis of the microphone pointing
towards the wind turbine, as in Figures 1 and 2. The board shall be circular with a diameter of
at least 1,0 m and made from material that is acoustically hard, such as plywood or hard chip-
board with a thickness of at least 12,0 mm or metal with a thickness of at least 2,5 mm.
A larger board is recommended especially for soft ground. In the exceptional case that the
board is split (i.e. not in one piece) there are considerations; the pieces shall be level within
the same plane, the gap less than 1 mm, and the split must be off the centre line and parallel
with the microphone axis as shown in Figure 1a).
The windscreen to be used with the ground-mounted microphone shall consist of a primary
and, where necessary, a secondary windscreen. The primary windscreen shall consist of one
half of an open cell foam sphere with a diameter of approximately 90 mm, which is centred
around the diaphragm of the microphone, as in Figure 2.
The secondary windscreen may be used when it is necessary to obtain an adequate signal-
to-noise ratio at low frequencies in high winds.
For example, it could con
...
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