SIST EN 61265:2002

SLOVENSKI STANDARD
SIST EN 61265:2002
01-september-2002
Electoacoustics - Instruments for measurement of aircraft noise - Performance
requirements for systems to measure one-third-octave band sound pressure
levels in noise certification of transport-category aeroplanes (IEC 61265:1995)
Electroacoustics - Instruments for measurement of aircraft noise - Performance
requirements for systems to measure one-third-octave band sound pressure levels in
noise certification of transport-category aeroplanes
Elektroakustik - Geräte zur Messung von Flugzeuggeräuschen - Anforderungen an die
Eigenschaften von Systemen zur Messung von Schalldruckpegeln in Terzbändern bei
der Zertifizierung von Flugzeugen der Transport-Kategorie
Electroacoustique - Instruments pour la mesure du bruit des aéronefs - Prescriptions
relatives aux systèmes de mesure des niveaux de pression acoustique par tiers
d'octave, pour la certification acoustique des avions de transport
Ta slovenski standard je istoveten z: EN 61265:1995
ICS:
17.140.30 Emisija hrupa transportnih Noise emitted by means of
sredstev transport
49.020 Letala in vesoljska vozila na Aircraft and space vehicles in
splošno general
SIST EN 61265:2002 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 61265:2002

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SIST EN 61265:2002

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SIST EN 61265:2002

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SIST EN 61265:2002

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SIST EN 61265:2002

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SIST EN 61265:2002
CEI
NORME
IEC
INTERNATIONALE
1265
INTERNATIONAL
Première édition
STANDARD
First edition
1995-04
Electroacoustique –
du bruit des aéronefs –
Instruments pour la mesure
mesure
relatives aux systèmes de
Prescriptions
pression acoustique par tiers
des niveaux de
acoustique
d'octave, pour la certification
de transport
des avions
Electroacoustics –
–
Instruments for measurement of aircraft noise
requirements for systems to measure
Performance
one-third-octave band sound pressure levels
in noise certification of transport-category
aeroplanes
Droits de reproduction réservés — Copyright — all rights reserved
© CEI 1995
n may be reproduced or utilized in
Aucune partie de cette publication ne peut être reproduite ni No part of this publicatio
any form or by any means, electronic or mechanical,
utilisée sous quelque forme que ce soit et par aucun pro-
including photocopying and microfilm, without permission
cédé, électronique ou mécanique, y compris la photocopie et
les microfilms, sans l'accord écrit de l'éditeur. in writing from the publisher.
Genève, Suisse
Bureau Central de la Commission Electrotechnique Internationale 3, rue de Varembé
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International Electrotechnical Commission
PRICE CODE
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Pour prix, voir catalogue en vigueur •
•
For price, see current catalogue

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SIST EN 61265:2002
1265 ©IEC:1995 — 3 —
CONTENTS
Page
FOREWORD 5
INTRODUCTION 7
Clause
1 Scope and object 9
2 Normative references 9
11
3 Definitions
15
4 Requirements
Annexes
25
A Bibliography
27
B Methods of testing the electroacoustical performance of a measurement system

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SIST EN 61265:2002
1265 ©IEC:1995 — 5 —
INTERNATIONAL ELECTROTECHNICAL COMMISSION
ELECTROACOUSTICS -
INSTRUMENTS FOR MEASUREMENT OF AIRCRAFT NOISE -
PERFORMANCE REQUIREMENTS FOR SYSTEMS TO MEASURE
ONE-THIRD-OCTAVE-BAND SOUND PRESSURE LEVELS IN NOISE
CERTIFICATION OF TRANSPORT-CATEGORY AEROPLANES
FOREWORD
1) The IEC (International Electrotechnical Commission) is a world-wide organization for standardization comprising all national
electrotechnical committees (IEC National Committees). The object of the IEC is to promote inte rnational cooperation 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 na tional 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 condi tions determined by agreement between the two organizations.
2) The formal decisions or ag reements of the IEC on technical matters, prepared by technical committees on which all the Na tional
Committees having a special interest therein are represented, express, as nearly as possible, an inte rnational consensus of
opinion on the subjects dealt with.
form of recommendations for inte rnational use published in the form of standards, technical reports or guides
3) They have the
and they are accepted by the National Committees in that sense.
tional Committees undertake to apply IEC International Standards
4) In order to promote international unification, IEC Na
tional and regional standards. Any divergence between the IEC
transparently to the maximum extent possible in their na
Standard and the corresponding national or regional standard shall be clearly indicated in the latter.
International Standard IEC 1265 has been prepared by IEC technical committee 29: Electroacoustics.
The text of this standard is based upon the following documents:
DIS Report on voting

29/289/RVD
29(CO)216
Full information on the voting for the approval of this standard can be found in the repo rt on voting
indicated in the above table.
This International Standard cancels and replaces IEC 561 in its entirety. The present standard was
prepared to incorporate improvements in instrumentation, following a request to the IEC by the
ational Civil Aviation Organization (ICAO) to develop specifications for digital equipment for use in
Intern
rtification.
aircraft noise measurement and analysis for the purpose of noise ce
Annexes A and B are for information only.

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SIST EN 61265:2002
1265 © I EC:1995 – 7 –
INTRODUCTION
ormance of instruments
rf
This International Standard provides requirements for the electroacoustical pe
(that may be components of a complete system) for measurement of the sound produced by aeroplanes
in flight or by an aeroplane engine installed on an outdoor test stand. Methods are also indicated by which
ormance of such instruments may be tested periodically.
the perf
ification are described in Volume I of
rt
Measurement and data-analysis procedures for aircraft noise ce
Annex 16 to the Convention on International Civil Aviation, with further guidance and descriptions of
Environmental Technical Manual prepared by the ICAO
acceptable "equivalent procedures" given in the
Committee on Aviation Environmental Protection (CAEP), (see annex A). The procedures include
measurement and analysis of the sound from aircraft in flight, and, in some circumstances, of the sound
from static engines under test, under given operating and atmospheric conditions.

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SIST EN 61265:2002
1265 ©IEC:1995 — 9 —
ELECTROACOUSTICS -
INSTRUMENTS FOR MEASUREMENT OF AIRCRAFT NOISE -
PERFORMANCE REQUIREMENTS FOR SYSTEMS TO MEASURE
ONE-THIRD-OCTAVE-BAND SOUND PRESSURE LEVELS IN NOISE
CERTIFICATION OF TRANSPORT-CATEGORY AEROPLANES
1 Scope and object
This International Standard specifies requirements for the electroacoustical performance of systems of
instruments used to measure sound for the purposes of aeroplane noise certification, and recommends
rformance continues to comply with
methods by which tests may be made periodically to verify that the pe
the requirements given within stated tolerances.
In general, a sound measurement system for this purpose comprises a combination of instruments
extending from a microphone through data recording and processing devices to a suitable output.
Particular measurement systems, differing in their composition, perform the necessary functions in
different ways and operate on either analogue or digital principles.
ational Standard is to ensure that different measurement systems have the same
The purpose of this Intern
electroacoustical characteristics within the stated tolerances under specified reference environmental
is standard does not provide recommendations for installation of microphones or
conditions. Th
microphone windscreens, nor requirements for measurement and analysis procedures used in aeroplane
ormance specifications for the measurement systems used to
rf
noise certification, but gives only the pe
provide one-third-octave-band sound pressure levels averaged over a period of time.
ain of the requirements apply to the complete measurement system, including any means of recording
Cert
a time waveform of the sound pressure signal to be measured prior to analysis. Other requirements apply
specifically to the microphone which generates an electrical signal in response to the sound pressure
received. Still further requirements apply only to the instruments used to operate on that signal in order
to provide an output in the form of one-third-octave-band sound pressure levels.
The requirements of this International Standard apply to the instruments used to measure the sound
produced by jet- or propeller-driven transport-category aeroplanes of maximum certificated takeoff mass
over 9 000 kg, or their propulsion systems when installed on a suitable outdoor engine test stand.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute
provisions of this International Standard. At the time of publication, the editions indicated were valid. All
rties to agreements based on this International
normative documents are subject to revision, and pa
Standard are encouraged to investigate the possibility of applying the most recent editions of the
normative documents indicated below. Members of IEC and ISO maintain registers of currently valid
International Standards.
International Electrotechnical Vocabulary (lEV) – Chapter 801: Acoustics and
I EC 50(801): 1994,
electroacoustics

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SIST EN 61265:2002
IEC:1995
1265 © – 11 –
IEC 801-2: 1991,
Electromagnetic compatibility for industrial-process measurement and control
equipment – Part 2: Electrostatic discharge requirements
IEC 801-3: 1984, Electromagnetic compatibility for industrial-process measurement and control
equipment – Part 3: Radiated electromagnetic field requirements
IEC 942: 1988, Sound calibrators
IEC 1094-3: 199x, Measurement microphones – Part 3: Primary method for free-field calibration of
(in preparation) 1)
laboratory standard microphones by the reciprocity technique
IEC 1094-4:199x, Measurement microphones – Part 4: Specifications for working standard microphones
(in preparation) 2)
3)
IEC 1260: 199x, Electroacoustics – Octave-band and fractional-octave-band filters (in preparation)
3 Definitions
For the purposes of this Inte rnational Standard, the following definitions apply. Definitions are consistent
with corresponding definitions in IEC 50(801).
Combination of instruments used for the measurement of sound pressure
3.1 measurement system:
levels, including a sound calibrator, microphone system, signal recording and conditioning devices, and
a one-third-octave-band spectrum analysis system.
NOTE – Practical installations may include a number of microphone systems, the outputs from which are recorded
simultaneously by a multi-channel recording device. The signal recording and conditioning devices and/or the spectrum analysis
system may have separate channels in parallel, again with facilities for selection, either of the input or of the output. For the
purpose of this standard, each combination of a single microphone system and a single data-recording and data-analysis
rises a separate, complete measurement system, and the requirements apply
channel within the other instruments comp
accordingly.
3.2 Components of the measurement system which produce an electrical output
microphone system:
signal in response to a sound pressure input signal, and which generally include a microphone, a
preamplifier, extension cables, and other devices as necessary.
Angle expressed in degrees between the p rincipal axis of the microphone,
3.3 sound-incidence angle:
as defined in IEC 1094-3 and IEC 1094-4, and a line from the sound source to the centre of the
diaphragm of the microphone.
NOTE – When the sound incidence angle is 0°, the sound is said to be received at the microphone at "normal incidence"; when
the sound incidence angle is 90°, the sound is said to be received at "grazing incidence`.
reference direction: Direction of sound incidence specified by the manufacturer of the microphone,
3.4
relative to a sound incidence angle of zero degrees, in which the free-field sensitivity level of the
microphone system is within specified tolerances.
For a sinusoidal plane progressive sound wave
3.5 free-field sensitivity of a microphone system:
of specified frequency, at a specified sound-incidence angle, quotient expressed in volts per pascal of
the root-mean-square voltage at the output of a microphone system by the root-mean-square sound
pressure that would exist at the position of the microphone in the absence of the microphone.
Document circulated as a Draft International Standard under reference 29/294/DIS.
1)
2) Document circulated as a Draft International Standard under reference 29/295/DIS.
3) Document circulated as a Draft International Standard under reference 29/292/DIS.

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SIST EN 61265:2002
1265 ©IEC:1995 –13 –
In decibels, twenty times the logarithm to the
free-field sensitivity level of a microphone system:
3.6
base ten of the ratio of the free-field sensitivity to the reference sensitivity of one volt per pascal.
NOTE —The free-field sensitivity level may be determined by subtracting the sound pressure level (expressed in dB re 20 t Pa)
of the sound incident on the microphone from the voltage level (expressed in dB re 1 V) at the output of the microphone system,
and adding 93,98 dB to the result.
In decibels, ten times the logarithm to the base ten of
3.7 time-average band sound pressure level:
the ratio of the time-mean-square of the instantaneous sound pressure during a stated time interval and
in a specified frequency band, to the square of the reference sound pressure of twenty micropascals.
In decibels, setting of the controls provided in a measurement system for the recording
level range:
3.8
and spectral analysis of a sound pressure input signal.
In decibels, sound pressure level produced, under reference
3.9 reference sound pressure level:
environmental conditions, in the cavity of the coupler of the sound calibrator that is used to verify the
overall acoustical sensitivity of a measurement system.
In decibels, level range for verifying the acoustical sensitivity of the
3.10 reference level range:
measurement system, and containing the reference sound pressure level.
Nominal frequency, expressed in hertz, of the sinusoidal sound pressure
3.11 reference frequency:
signal produced by the sound calibrator.
3.12 level difference: In decibels, measured one-third-octave band output signal level on any level
range, adjusted for the nominal difference between the settings of the level range controls on the level
range and the reference level range, minus the level of the corresponding electrical input signal.
In decibels, level difference on the reference level range for a reference
3.13 reference level difference:
electrical input signal corresponding to the reference sound pressure level.
In decibels, level difference on any level range, at a selected one-third-octave
3.14 level non-linearity:
midband frequency, minus the reference level difference, all input and output signals being relative to the
same reference quantity.
In decibels, for a stated level range, range of levels of steady sinusoidal
3.15 linear operating range:
electrical signals applied to the input of a measurement system exclusive of the microphone system,
extending from a lower boundary to an upper boundary, over which the level non-linearity is within
tolerances specified in 4.5.2.

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SIST EN 61265:2002
–15 –
1265 ©IEC:1995
4 Requirements
4.1 General
The measurement system shall provide time-average one-third-octave-band sound pressure levels in
decibels covering at least the range of nominal midband frequencies from 50 Hz to 10 kHz, in accordance
with the requirements and recommendations of ICAO Annex 16 and the ICAO Environmental Technical
Manual (see annex A).
Measurement systems in which an analogue input signal is converted to a digital signal that is recorded
shall include an anti-alias filter before the analogue-to-digital conversion.
NOTE –The cut-off frequency of the anti-aliasing filter should be less than 0,5 times the sampling frequency.
Methods for periodic tests of the electroacoustical performance of a measurement system giving results
which are suitable for comparison with the requirements of this standard are described in annex B. The
results of any such tests shall be adjusted to correspond to reference environmental conditions (see 4.2).
4.2 Reference environmental conditions
Reference environmental conditions for specifying the performance of a measurement system are:
20 °C
- air temperature
101,3 kPa
- static air pressure
- relative humidity 65 %
4.3 Sound calibrator
The sound calibrator used to check the overall acoustical sensitivity of the measurement system shall
meet at least the Class 1L requirements of IEC 942. The reference sound pressure level produced in the
cavity of the coupler of the sound calibrator shall be calculated for the reference environmental conditions
of 4.2
...